40 Button Lachenal Anglo Restoration

I recently fully-restored a 40-button Lachenal Anglo. It was in pretty poor condition when I received it. The wooden ends were non-original, damaged, and not very well made.


The bellows may have been original, but they were worn-out and patched.

There was significant damage to the woodwork, including a couple of split reed chamber walls.

The pads were mostly dust held together with blobs of sealing wax, and the springs were mostly non-original and much too strong, probably in a vain attempt to make the knackered pads seal.

Step 1: remove the old bellows.

The bellows frames weren’t too bad underneath, apart from a few loose/missing corner blocks.

Next I dismantled the actions, laying the levers out on a piece of card so I could figure out which was which when it came time to reassemble the instrument. Quite a few of the action box walls had come apart at the glue joints, but the wood wasn’t too damaged.

Most of the end bolts and corresponding nut plates were worn out, probably due to somebody over-tightening them in an attempt to make the instrument airtight (unsuccessfully, because the various boards had all warped).

I already wrote an earlier blog post about making the new end bolts. I also made and fitted a new set of nut plates from thicker brass (3mm rather than 2mm), so they will hopefully be less prone to stripping in the future. The new wood screws are stainless steel and slightly longer than the originals. I plugged up the old screw holes with matchsticks before fitting the new screws.

The end bolt holes in the action box walls were worn oversized (particularly at the tops, where the screw heads had sunk through the end plates and worn a deep gouge), so I plugged them all with beech dowels.

I glued the walls back together in a band clamp using hot hide glue. Unfortunately the top and bottom halves didn’t quite match up perfectly, which I later realised must be because they originally came from different instruments (they are a different wood, and the pad gouges on the inside of the top walls don’t marry up with the positions of the pads).

I used a simple jig to re-drill the end bolt holes a consistent distance from the outside of the instrument.

Then I clamped the bellows frame to the bottom half of the action box and drilled the tapping holes in the nut plates.

Once I’d got a couple of them drilled, I used spare drill bits to keep them aligned to each other while I drilled the other four.

I took the plates off again to tap them, to avoid embedding a lot of greasy swarf inside the bellows frames for perpetuity.

As I mentioned previously, two of the reed chamber walls had split. I could have attempted to glue them back together but I doubt it would have held up for long, so I unglued them (hot water to soften the hide glue, and waggling until it suddenly came free like a loose tooth).

I glued new quartersawn sycamore walls in place, with hide glue again, using the reed as a wedge to hold it in place while the glue dried.

One reason why this wall was weak was that part of it needs to be cut away to make space for the valve in the next-door chamber. I thought it best to chisel this out in-situ.

I used a combination of needle file and skew chisel to undercut the new wall for the dovetailed reed slots.

Both the action boards were badly warped, so they didn’t seal properly to the tops of the reed pan walls. I cured this by painstakingly lapping them using a sheet of sandpaper glued to glass. I don’t seem to have a picture of it, but I also inlaid a piece of sycamore to repair the deep gouge visible in this one where the sound post screw goes through it.

On the right hand reed pan, it was so hollow near the sound post screw hole that I decided to glue a piece of veneer to the area to build up the thickness before lapping most of it away. This incidentally also filled in the oversized gouge around the screw hole.

The reed pans were warped too, though sadly not in a way that matched the warping of the action boards, so I also had to lap the tops of the walls. To avoid removing too much depth from the chambers, I had to glue tapered shims to the tops of about half of the walls near the outer edge.

After getting the tops of the reed pans flat, I replaced all the support blocks in the bellows frames. This is far easier to do without the bellows in the way, hence why I did all the above work prior to making the new bellows.

This shows why you sometimes find a block or two that isn’t right in the corner of the bellows frame.

The woodwork repairs done, I made and fitted new chamois leather gaskets. Not pictured, it was necessary to fit card shims to the inside of the bellows frames before the chamois to get the pans to fit tightly.

I have recently bought an old picture framing mat board cutter. This tool makes it much easier to cut the bellows card into strips, bevel the top edges at 45°, and with a simple jig, cut the strips into individual cards. Incidentally I switched from 1.5mm thick greyboard to 1mm thick millboard. It is a little more flexible but the reduced thickness really makes the bellows feel a lot less bulky. I think it’s a better quality material too, and likely to last longer.

After my experiment with self-adhesive hinge linen on the last set of bellows, I went back to Fraynot linen cut on the bias, attached with a bookbinders’ starch paste. The resulting hinges are thinner and much more supple.

Because I originally made my bellows mould to fit a set of bellows that came off a 6″ instrument, and this was a 6 ¼” instrument, I had to pack them out a little using strips of thin plywood between the core and the forms.

This time I prepared all of the leather parts before starting to glue them on. I also refined the shape of the gussets a little, and skived most of the parts slightly thinner than on previous bellows.

The bellows immediately after taking them off the mould! They are initially quite stiff and need to be broken in. In order to maximise their useful range, I spent the next few weeks while I was working on other parts of the restoration alternating between squeezing them fully closed in my bellows press and stretching them fully open using a couple of the forms from the bellows mould, exercising them a bit every time I handled them. I think this treatment along with other improvements really helped; the finished bellows are the most supple I have made to date.

A set of reproduction Lachenal bellows papers really helped them to look the part.

I recently bought a small Eclipse fretsaw frame that is the ideal size for concertina ends; much less tiring to use than a standard large fretsaw frame. I had to make new blade clamps because the old ones had stripped threads. I made the new clamps from scraps of tool steel and hardened them, so they ought to last pretty much forever now! I also made a new saw table with a nice big flat rigid top.

This shows why I made the top of the saw table so high; I prefer to do piercing standing up, and this height results in my arms being in the most comfortable position.

I cut the new ends from 22 S.W.G nickel silver (German silver) sheet, starting by roughly cutting them out oversize with a slitting blade in an angle grinder.

The fretwork design is based on photos I found online of a vintage Lachenal 40-button, but I redrew it and modified it a little (eliminating the redundant unused button holes on the opposite side from the thumb button on each side).

I drilled all the holes first. The bolt holes are actually transferred from the action box frames, not the template. I later realised the button holes should have been a bit larger to give more clearance around the buttons, so I had to enlarge them after I had cut all the fretwork.

Piercing in progress. I actually find this one of my favourite parts of the job; my mind goes into a flow state, and when I emerge some hours later I have made a beautiful thing.

I’m going to skip over a few days of toolmaking here; I may come back later and write a separate post about it. I made a press tool modelled on the one used by the Crabb company, which crimps the edges of a metal end plate one side at a time.

The side on the left has been crimped, the tool is about to press the side in the middle:

After pressing:

The end result. I found I had to do some manual cleanup work to neaten it where it hadn’t worked perfectly, particularly in places where the piercings were quite close to the border.

I polished the finished ends using my Bridek polishing spindle and various Menzerna compounds.

The button peg holes in the action boards were both worn oversize, and probably no longer exactly aligned with the button holes in the new ends, so I decided to plug them all with beech dowels and re-drill them.

I made this tool to drill the button peg holes; the brass bush is the right size to slide in the button hole and guide the drill bit to the right location in the action board. I used the depth stop on my drilling machine to make sure I didn’t quite drill all the way through the board.

You can see in this one that the new holes are sometimes slightly off from where the old ones were; if I hadn’t re-drilled them, the buttons wouldn’t have lined up right, which would probably have caused them to stick.

In order to bush the button holes, I needed to screw a piece of plywood to the underside of the end plate so I could glue the bushes into that rather than trying to glue them directly to the thin metal. (I later cut the board to match the fretwork.)

A different special tool used to accurately locate the pilot holes in the bushing board.

I fitted loudspeaker grille cloth below the fretwork. It proved a bit tricky to get the button holes in the right places; I settled on making a card template, then placing the template over the fabric, cutting around it with a rotary cutter, and punching the holes through the card and fabric both.

I glued the fabric to the underside of the metal with PVA (rather a fiddly job to avoid baggy areas or holes not lining up). One side-effect of this was that the acidic fumes given off by the glue oxidised the polished surface of the metal, and of course I couldn’t just take them back to the polishing machine because it would probably damage the cloth. I managed to clean it off with dry jewellery polishing pads but it was a bit annoying. Perhaps epoxy would be a better choice.

I laser-printed a replacement maker’s logo on archival paper and stuck it on with PVA.

This is a taper reamer I made from silver steel to slightly taper the holes in the bushing boards. By making the holes looser at the bottom than the top, they are better able to cope with any slight misalignment than if the sides of the holes were parallel.

Similarly, I made a new bushing reamer that is continuously tapered, thus making the bushes looser at the bottom. You can also see in this picture that I cut the boards closely to the outline of the fretwork and coloured the edges black so you can’t see them under the grille cloth.

Lachenal action levers sometimes wear in a way that causes them to twist as they pivot, causing uneven movement and pads not seating properly. The way I fix this is by building up silver (hard) solder on the worn area of the lever, then filing it back until it fits well again. Usually the post isn’t badly worn enough to need the same treatment. I had to do this repair to about half a dozen of the levers on this instrument.

Cleaned and rebuilt actions, with new springs, bushes, dampers, pads, etc.:

My first attempt at the elongated air hole pad was to cut it from the same leather/felt/card sandwich as the ordinary pads. It sort of sealed, but would leak when you pressed the bellows hard. I worked out that it was because the card was too flexible; the ends of the pad were flexing up and letting air leak out. I fixed this problem by making a special pad with a top layer made from thin stainless steel sheet instead of card.

Skipping over a bunch of toolmaking again; I made a set of dies to punch my own valves to a consistent range of sizes. I also got hold of some special thicker (very expensive) leather that is better-suited for the largest valves. I made the new valve restraint pins from 24 S.W.G. stainless steel spring wire. I have switched to using gum arabic to glue the valves to the reed pans; it is plenty strong enough when dry, easy to use and non-messy, and very easily removed with a little warm water on a cotton bud when you need to replace a problematic valve. I lightly cleaned all the reeds, and where necessary shimmed the slots in the reed pan to get the reeds to fit snugly.

The strap-adjuster thumb screws were the wrong ones for the instrument; the thread didn’t fit the captive nuts. To cut a long story short, I decided to make all new nuts and screws with an M3 thread.

Luckily I was able to reuse the tiny wood screws; finding replacements for them might have been tricky.

I’m quite proud of these thumb screws; it may seem like a trivial detail but the first ones I made were pretty bad in comparison, and I really think I have got the hang of them now. If you dig back through my Instagram page, somewhere in there is a post describing my process.

There’s quite a bit going on in these next two pictures. Firstly, notice the bottom half of the wall is ebony (original to this instrument), the middle section is mahogany (probably came from a different vintage instrument), and then there’s what appears to be another ebony section between the mahogany and the metal plate. I needed to add the second black section as a spacer to make the boxes a bit deeper, because the action levers were hitting the bushing boards. It is made from a manufactured ebony substitute called Rocklite Ebano. Although I needed to do this for mechanical reasons, I actually think the three-layer effect looks quite unique and attractive.

Secondly, I sanded and lightly French-polished the woodwork. I deliberately didn’t go overboard building up a high gloss, and I tried not to remove too much of the old patina in the process.

Thirdly, I made new brass strap rings (the loop thing that holds the strap down to the thumb rest), replaced the captive nuts in the ends of the handles with M3 ones, and made domed brass washers to hold the fixed end of the straps.

Fourthly, I made new leather hand straps. I don’t think I’ve quite got the pattern perfect yet (the ‘tails’ are about an inch too long), but I have figured out how to round and smooth the edges using an edge beveler and a burnishing spindle so they feel more comfortable on the hands.

When I received the instrument it was in C#/G#, old philharmonic pitch, which is about half a semitone higher than modern concert pitch. In consultation with the client, we decided I would re-tune it up to D/A concert pitch. Actually, I later realised that it may have originally started out as D/A old pitch and been tuned down to C#/G#, because the note stamps on the frames made more sense if that was the case. Most of the reed tongues were steel but there were a handful of brass ones in there too; you have to be very gentle with them as a tiny amount of filing can cause a big shift in the pitch, much more so than with steel ones.

The highest reed on the instrument was missing. I worked out from button charts that it was supposed to be a very high F#. I made a replacement, making an educated guess as to the length of the vent. It was so small that I didn’t have an end mill that could cut the vent slot so I did it by hand with a jeweller’s saw and tiny files (not as difficult as it sounds, though a little time-consuming to get it perfect). After experimenting with the profiling for a while, I managed to get it sounding remarkably well on the tuning bellows. Unfortunately once in the instrument, this reed, along with the other three or four highest notes, were pretty unresponsive, needing quite a high bellows pressure to get them to start. After quite a long time spent experimenting with them, I came to the conclusion that the problems mostly came down to the reed chambers being too large.

The worst one would barely speak at all (the one on the bottom side of this chamber; it is quite a lot higher in pitch than the corresponding top-side reed). I managed to significantly improve it by replacing the end wall with one closer to the vent slot so as to reduce the chamber volume.

My highest reed was in an inboard chamber. I managed to improve its response by making a little removable block that significantly reduces the dead volume in the chamber.

The finishing touch was to add my mark to one of the reed pans.

I had one or two bits left over after I finished putting it back together!

The finished instrument (photo courtesy of the instrument’s owner, Wallace Calvert). I am particularly proud of how nicely the new end plates turned out.

And now for a special treat, here is a clip of Wallace playing The Humours of Tullycrine on the instrument:

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Turning End Bolts

On my first instrument, the ends were held on with commercially-made stainless steel allen-head M3 screws. They work fine, but I felt they gave the instrument a bit of a modern, almost industrial look.

I am currently working on restoring a vintage Lachenal Anglo for a client, and the end bolts and captive nuts are missing or badly worn due to past over-tightening (probably from trying to cure leaks that were actually due to internal structural problems). Needless to say, it wouldn’t have been appropriate to replace them with modern screws. Rather than try to source a better second hand set from a parts dealer, I decided it was time to figure out how to make my own new brass end bolts from scratch.

I sourced some 4.5mm diameter free-machining brass bar. The finished heads want to end up about 4.5mm, so I need to avoid turning it any smaller in the process. It came in 330mm lengths, which I figured out would comfortably make eight bolts if I cut it into four sections.

One bit ended up too short due to a mistake. Incidentally I used to think junior hacksaws were rubbish until I got some better quality Sheffield-made blades and found this excellent frame for a pound at a car boot sale. It tensions the blade really tight, which prevents it flexing in the cut, and the aluminium handle is really comfortable.

If I’d only been making a small number of them I probably would have held the blanks in the three jaw scroll chuck and accepted that they would turn out slightly non-concentric, but since I needed to make a large batch and will be making more in the future, I decided I wanted to use a collet instead. Taig (the manufacturer of my lathe) sells a few standard imperial-size collets, and blanks that you can drill to whatever size you want. I’ve had this lathe for probably fifteen years and this is the first time I have ever used one of the blank collets! They are made from a nice free-machining steel that drills very easily:

The difficult part is holding the awkwardly-shaped piece of metal while you cut the slots in it. I settled on putting a piece of the 4.5mm brass in it, and holding that in the vice instead of the collet.

Once I had sawn the first slot, I turned it 90° and used the slot in the brass bar to guide the saw while I cut the second slot. Then I flipped it over and cut the other two slots.

The finished collet. Not too bad for a junior hacksaw.

The first step in machining the bolts was to put the blank in the collet with enough protruding for a single bolt, then turn down the shaft to 2.25mm. Before doing the job, I spent a long time worrying about how I would do this without the shaft flexing away from the tool towards the end, resulting in it getting fatter towards the tip. This wasn’t as much of a problem as I expected it to be. Getting the tool bit really sharp and running the lathe at its maximum speed was a good starting point.

The first method I found was to turn the first third of the shaft to finished diameter a bit at a time, then move along and turn the second two thirds to finished diameter. This worked fine but took a couple of minutes per bolt. I found I could take heavier cuts on the second section, then I got to experimenting to see how far I could push it, and to cut a long story short, it turns out that it’s perfectly possible to turn the entire thing to finished diameter in one pass! Once I figured this out, it sped things up quite a lot. It’s important that you do it in one pass, because you need the full diameter of the bar to the left of the tool to support the cut. If you try to do a second cleanup pass, however light, the bar will flex at the end. Here’s a video clip to prove it:

Next I used a fine single-cut file to put a blunt point on the shaft.

Then I used a tailstock die-holder and a good quality sharp HSS die to cut the threads. I used a dab of cutting oil (it really makes a noticeable difference to how easily the die cuts) and turned the spindle by pulling on the drive belt, using a ruler to measure when the tailstock had moved far enough for the desired length of thread. The video above also shows the thread cutting operation.

A brief digression about the threads: the original Lachenal bolts are about 2.25mm major diameter, but a relatively coarse pitch. I haven’t been able to find any standard thread that matches it. Since I don’t have a screw-cutting lathe, to copy it I would have had to commission a specially made tap and die set, which would have been very expensive. I instead decided to use 8BA, which has the same diameter but a finer pitch. I don’t think this is a problem for the restoration because I am replacing all the bolts and captive nuts at the same time. From what I have read, the Crabb company used 8BA bolts in their instruments too.  BA threads are mostly obsolete now apart from a few niche applications, but you can still get hold of new taps and dies for them.

After doing all the above steps to one end of the blank, I turned it around and did the same to the other end. I probably could have used slightly shorter blanks, it just worked out this way when I cut the bar stock into four.

Next I needed to cut the piece into two and form the domed heads. To do this efficiently I got a ¼” HSS tool blank and ground a special profile onto it. This profile first parts off the stock to length, then you carry on plunging it and it forms the domed shape.

Here’s a video of the process showing how quick it is:

Next I cut the slot in the head using a HSS slitting saw, 50mm diameter by 0.6mm thick with 100 teeth. I didn’t have a mandrel with the right centre diameter, but Taig sells blank mandrels that screw onto the headstock so you can turn a custom spigot to fit your saw blade. Luckily I have an older-model Taig milling machine that has the same headstock on it as my lathe; newer mills come with an ER16 collet chuck instead, which makes this sort of thing a bit more complicated because you can’t just transfer something straight from the lathe headstock to the mill.

A nice snug fit on the mandrel:

Next, I needed to make a special fixture to hold the bolts on the milling machine while cutting the head slot. I made the top part from aluminium, and the nut bar from mild steel. Tightening the set screw clamps the shaft of the bolt tightly.

The slitting setup on the milling machine:

Here’s a quick video clip of it cutting a slot:

Slitting the head of the bolt. #cncmilling #taigmill #concertinamaker

A post shared by Alex Holden (@alexholdenmaker) on

Although I did it with a short hand-written CNC program because I have a CNC mill, this operation would be dead easy on a manual mill or even a milling attachment on the lathe. I found that with the CNC mill, I could load a bolt in, hit Start, go back to the lathe, turn the head on the next bolt, and return to the milling machine around the time it finished cutting the slot.

Next I put the bolt back in the lathe and used 800 grit emery paper and the top speed to smooth out any tool marks and burrs.

Finally to the polishing spindle to give the head a shiny finish. This Menzerna 480W compound is very effective on brass.

I had to use a screwdriver to clean excess polishing compound out of the slot of each one.

Here’s the first one I made between a couple of different ones from the vintage Lachenal. My head is more closely based on the shallower one on the right.

I made a batch of about seventy bolts; enough for the Lachenal restoration and my next few instruments.

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Brun Part 5: Bellows

The fifth instalment in the story of building my first concertina is about the bellows. First I had to make a new, rectangular mould to assemble them on. The stock for the forms was constructed from strips of softwood glued across a plywood base, which I then ripped into four pieces.

I again milled the forms to shape on the CNC mill. One thing I did differently this time was to rough them out in staircase form with an ordinary ¼” end mill first before cleaning them up with the large V bit.

When I made the forms for the hexagonal mould, I cut straight into the material with the V bit using lots of shallow passes, which caused lots of noise and vibration, resulting in a poor surface finish. Removing most of the material with an end mill first gave much better results.

The wide forms stretched the machine to the absolute limit of its Y axis capacity.

The bandsaw I had at the time wasn’t capable of ripping the angles off the undersides of the forms, and I don’t own a table saw, so I did them with a hand rip saw instead.

The rectangular core was relatively simple to make compared to the previous hexagonal one.

I split both of the long sides to make the mould easy to remove from the finished bellows.

Cutting the cards by hand with a craft knife. I hate this part; it makes my knife hand ache for days afterwards. Also, because this set of bellows was meant to be relatively heavy-duty for a ‘travel’ instrument, I chose to use thicker 1.5mm card rather than the standard 1mm stuff I used on the tuning bellows (in hindsight this may not have been a good idea because it made the bellows a bit bulkier). I have since bought a special card cutting guillotine that in the future will make this operation much quicker and easier.

Rounding the corners of the cards with a gouge. I started off pressing down onto the bench, but I found it was easier to put a cutting board in the vice and lean against the gouge handle with my hip.

I rounded the tops of the cards on a linisher (bench mounted belt sander) with an 80 grit belt. In hindsight I should have done this outdoors because everything in the garage including my car wound up covered in a thick coating of fine grey dust!

The rounded top of a card. This gives a nice shape to the peaks of the bellows folds, though in hindsight it would have looked better still if I had rounded the pointy corners a bit more.

I decided to try hinging the cards together with a self adhesive linen hinge tape made for bookbinding and other card related crafts. The roll was quite wide so I cut it in half. This picture shows the result of a strength test: the surface of the card ripped off before the glue or the linen failed (and it took quite an excessive amount of force to do so).

I started by hinging the cards together on the inside. The peak hinges can be taped with the cards laying flat, but it’s better to do the valley hinges with each pair of cards in the closed position (or flat but with spacers holding a slight gap between them), otherwise they will later resist closing.

I folded them up and clamped them tightly like this for a couple of days to help the tape glue to really bond well to the cards. Note that the end cards are slightly taller because the end boxes are about ¼” bigger than the bellows. This is partly cosmetic and partly to avoid the bellow peaks touching the table when you put the concertina down.

Next I tied the sets of cards to the mould with plastic coated gardening wire. Elastic bands would probably have been easier but I didn’t have any long enough. Note that the bellows frames aren’t attached to the mould. This wasn’t possible with this instrument because the frames have a divider across them due to the split reed pan design.

I ran the self adhesive linen tape all the way around each peak. This gives a stronger bellows than if you just put small pieces on each corner.

Afterwards I took the full set of cards off the mould and again pressed it tightly for a day or two to help the top hinges stick as well as possible. You can see in this picture what I meant about how it would have looked neater if I had rounded the corners of the cards a bit more.

I needed wider hinge strips on the end cards to attach the bellows to the frames, so I cut those from the ‘Fraynot’ hinge linen from Shepherds bookbinders’ suppliers that I used for all the hinges on my tuning bellows. I cut it on the bias to make it less likely to fray or rip.

Then I glued them on. From this point on, I used hot rabbit-skin glue for everything except the decorative papers.

A brief digression about my experience with the self adhesive hinge linen. In future I’m going to go back to using the Fraynot linen cloth for everything. Although the self adhesive tape worked fine and I don’t think it’s likely to come apart, I found that I much prefer working with the Fraynot and a liquid paste/glue, because if it goes on wonky you can peel it straight off and reposition it, whereas the self adhesive tape sticks instantly and you have to tear the surface of the card to get it off again, then throw away that strip of tape. The tape is surprisingly expensive too, though that’s not my primary consideration. It also had quite a lot of wrinkles in it where the cloth had stuck to itself during manufacturing and the glue is so strong it’s not possible to pull the wrinkle out; sometimes I had to waste a section of it to avoid putting a wrinkled piece on the bellows where it would be visible through the leather. Most importantly, I believe the hinges I get with strips of cloth are noticeably thinner and more supple than with the tape. The difference is fairly subtle when looking at a single hinge, but an entire bellows set with hinges on both sides of the peaks feels relatively stiff and bulky when assembled with the self adhesive tape. Although it’s possible the tape is made from a heavier cloth, I suspect the main difference is in the properties of the glue. I have found that traditional wheat paste doesn’t noticeably stiffen the hinge at all, whereas rabbit glue does stiffen it a little initially but after working it for a while it ‘breaks in’ and becomes supple again. Whatever is on the self-adhesive tape has a rubbery feel to it, and seems to add a bit to the thickness of the hinge too.

I covered the bellows with a nice brown goatskin leather from Hewit, cutting it into strips with an Olfa rotary cutter, which really cuts very nicely, much easier to use than a craft knife.Using my Scharffix 2000 to pare the leather down.

Thanks to a thread on the concertina.net forum, I learned that Israeli-made Personna safety razor blades fit the Scharffix and cut really well, better even than the thicker OEM blades that came with the machine. It’s crucial with this machine to use ultra-sharp blades, otherwise it behaves terribly, stretching and ripping holes in the thin leather.

Checking the thickness of the valley strips.

And gluing them on:

 

Cutting out the gussets with a template and craft knife. This is rather a tedious job; a die tool would make it much quicker.

I use the Sharffix to do as much of the skiving as possible, but the gussets always need a bit of manual cleaning up afterwards with a skiving knife.

Gussets glued on. It proved rather a pain to get the bottom corners to fully stick to the valleys without leaving a little gap. I wound up waiting for them to initially dry, then adding a bit more glue to each gap with a tooth pick and pressing it down with a bone folder until it stayed in position. This is less of a problem with bellows that have more than four sides because you don’t have to stretch the gussets around such a tight angle.

I roughed up the tops of each gusset slightly with sandpaper before gluing the top runs over them.

Cutting more long strips of leather for the top and end runs. It’s a pain when the Scharffix goes wrong in the middle of one of these strips because you need the whole run to be good to avoid having more than one joint.

Top runs glued on.

Next I needed to take the bellows off the mould and attach them to the frames, starting with the hinge linen.

Now the end gussets. This was way more difficult to do neatly without the aid of a mould. It helped to use a stick clamped to the frames to hold them a fixed distance apart.

Finally the end runs. As I mentioned in part three, here’s where I realised I’d made a mistake in not making the bellows frames a tiny bit smaller than the action boxes, in order to hide the edge of the end run. I skived the edge down as close to nothing as I could and tried to get that skived edge flush with the edge of the frame, but it was impossible to get it absolutely perfect, so when I subsequently trimmed the extra off, the edge wasn’t infinitely thin any more so it is possible in places to see a tiny bit of unfinished leather. I recognise I am quite possibly being over-critical of my own work here!

Looking pretty good!

For the decorative papers, I took a sample of the leather down to my local craft shop and looked for a patterned decoupage paper that went well with it. This is what I found. I avoided cutting papers from the area near the bottom that looks dirty (the design is actually printed that way).

I spent a pleasant evening cutting out papers and pasting them on while watching TV programmes in the background.

The finished bellows. I think the papers really go quite well with the leather. Although they were still quite stiff and springy at this stage with a preference for remaining open, I subsequently spent quite a while pressing them and exercising them, and they gradually broke in and became easier to play.

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Brun Part 4: Actions

Part four of the story of how I made my first instrument is about the actions (i.e. the mechanisms that uncover holes and let air through a reed when you press a button).

I made the action boards from birch plywood on the CNC milling machine, which seemed to work pretty well. Although I’m sure high-quality plywood is a good choice for strength and stability, on the next instrument I may try making the action boards from solid wood instead to see if it has a beneficial effect on the tone.

Another thing I will probably do differently next time is to not drill the button peg holes at this stage using CNC. They need to be very accurately aligned with the button holes in the end plates for the buttons to work smoothly, and by doing it this way it took me a lot of fiddling about to get the two boards to line up well enough to avoid the buttons sticking. I think a more accurate way would be to bolt the action boxes together with the action boards inside, then use the pillar drill and spot through the end plate using a drill bit glued into a mandrel that is the same diameter as a button (not my idea: I recently heard about this technique via another maker).

The action boards sit in a rebate in the bottom half of the action boxes. The problems I had with the walls not gluing up perfectly square meant I had to make careful adjustments to the edges of the action boards to get them to fit snugly in the rebates while also accurately aligned with the button holes.

I turned a couple of cylindrical brass dies that mark a circle around each pad hole to help glue the pad in the right place.

Lots of pads.

I made a couple of button guide boards to hold them in the right place while gluing the pads on.

Fitting the cross hole bushes in the buttons (see my earlier article about how I made them) using Bob Tedrow’s method of pulling a strip of cloth through them all, then snipping them apart with scissors:

I cut the lever posts from 1.5mm brass on the CNC mill:

And the levers themselves from 1mm brass:

It took quite a lot of fettling with needle files and emery paper to clean them up. I put the pivot points at the half way points for reasons that made sense on the drawing board, however I have since learned that it is better to put them closer to the button if you can find the space to do so (this causes the pad to lift up by more than the distance the button travels down). In hindsight this may have helped with some of the issues I later had with ciphers because I could have reduced the button height by 0.5mm without compromising the amount of pad opening.


I already wrote about the die I made to thread the grommet ends of the levers, but I have since learned that I get a cleaner, more consistent result from it if I squeeze the tool in a vice instead of hitting it with a hammer.

Before and after forming the threads:

Riveting went fairly smoothly. I only had to redo a couple of them because the pivots tightened up.

The reason for the odd shape of the lever posts is so I could knock them in or pull them back out using a tool with a matching notch cut in it (not my original idea).

The tool has a flaw: because the socket is on an edge of the tool but you hit it in the centre, the force is transmitted to the post off-axis, which tends to cause it to go in at a slight angle. I had to straighten up each post with needle nose pliers after knocking it in. I will probably modify or remake the tool before the next instrument to prevent this happening.

All the levers and buttons installed. Unfortunately I discovered a significant problem at this point. The button ends of the levers were too fat, making them very stiff, especially on the shortest ones.

I didn’t want to pull them all out again, so I instead used a rotary burr and needle files to slim them down in situ, which solved the problem.

Some of the springs.

An action board with all the springs and pads installed. Some of the spring locations proved problematic due to lack of space around the middle row of pads, and I wound up spending quite a bit of time working on getting the button pressure consistent across the instrument while also eliminating ciphers (notes that don’t stop playing when you let go of the button). Most of the ciphers were caused by the end of a lever or part of a spring hitting the underside of the end plate; there was really almost no wasted height inside the boxes.

Adjusting the heights of the buttons to get them consistent is done by bending part of the lever it’s attached to. To make this easier I made a pair of special tools from old screwdrivers to grip the levers in situ.

Overall, I’ve learned that there’s nothing tremendously difficult about building a concertina action, but there are lots of little parts to make and it takes a great deal of patience to assemble and adjust it until it works smoothly, consistently and reliably.

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Reed Pan Router Bit

I’ve spent hours searching for a commercially-made router bit that has the right dimensions to cut the dovetail slots in a traditional reed pan. It needs to be an unusually small diameter, but if you want to be able to cut the top slots after installing the chamber side walls as it was done originally (some of them undercut the walls), it needs to have a disproportionately long ‘neck’ between the cutter and the shank. On the plus side, the slot is quite shallow so the neck doesn’t need to be ridiculously skinny. In the end I decided to make my own.

I started with a piece of 1/4″ silver steel. After putting it in a collet and facing the end, I used the side of a threading tool to turn the tapered section, being careful to produce a sharp corner without significantly reducing the diameter of the base of the cone. I made it just long enough to be able to cut a 2mm deep slot, to avoid weakening the neck section unnecessarily. I set the tool holder over to produce the desired 60° taper:

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Next I extended some more stock from the collet and turned the ‘neck’. On my first attempt, swarf obscured my view of the work and I accidentally retracted the carriage too far to the right and put a groove in the cone area. There was no option but to start again! The second time, I used the tailstock as a right-hand carriage stop to protect the cone.

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The trickiest part of making your own router bit is producing the flutes without a special tool cutter/grinder machine. I cut three helical flutes by hand with a very small triangular saw file, then hardened and tempered it and sharpened the edges with diamond needle files:

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Unfortunately it didn’t work well at all. It splintered the surface badly, then overheated:

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Back to the drawing board. I studied a lot of photos of commercial dovetail router bits on Google Images and came up with a very different two-flute shape. Here’s a quick clip of me filing the relief angles on the second router bit with my saw file (click to stop it after you’ve seen it once, because the Instagram player auto-repeats):

Filing relief angles onto the Mk II reed pan router bit. Quite a ticklish job. #concertinamaker #toolmaking

A video posted by Alex Holden (@alexholdenmaker) on

And this is the finished bit, after heat treatment and sharpening. The thing it’s inserted into is one of my milling machine’s quick change tool holders:

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This photo shows the reason why it needs a long neck (I made it a bit longer than would have been necessary for this Treble English, in case I want to make an instrument with deeper bass reed chambers at some point):

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The second router bit works pretty well. Here’s a clip of it cutting a reed slot in a piece of scrap pine:

Programming the CNC mill to machine the slots is surprisingly complicated. The CAM software I’m using doesn’t understand how to cut a pocket with a tool that can’t plunge straight the workpiece and needs to enter and leave the edge of the material. I found a way to trick it into doing what I need, but the entire process filled nearly two pages of my logbook, and I need to do it all again for every size of frame I need to cut!

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Another problem I ran into is that the outer dimensions of the antique Lachenal reeds I’ve been copying are a bit variable. Not by much, but a tenth of a mm change in width makes the difference between a snug fit and a loose one. This one fits very well – I can throw the block of wood in the air and catch it and the reed is still nicely seated – but the reed taken from the slot next to it (nominally the same frame size) is loose enough that it would fall out. I think when the instrument was built, somebody must have spent a while individually fitting each reed to its slot. Luckily my CNC mill (which I’m using for both the frames and pans) is repeatable to tight enough tolerances that I shouldn’t have this problem.

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Acetal Buttons

I made a batch of buttons for my first prototype instrument. For simplicity I decided to use solid black acetal (an engineering plastic, commonly called Delrin, though that is a trademark of DuPont) rather than metal. Acetal is used by most modern concertina makers and it has a number of useful properties; particularly ease of machining, low mass, low friction, and low thermal conductivity (i.e. they don’t feel cold to the touch). I believe the top quality instruments still tend to use hollow metal buttons though.

The acetal came through the post in 1m lengths protected by a plastic tube. Long lengths of it are quite bendy. I started with 6mm and turned it down to 4.8mm. Before putting it in the lathe I cut it into 250mm lengths, which was about as long as I dared (shorter would result in more wastage, any longer risks the unsupported left hand end whipping around dangerously). I got nine buttons from each length.buttons2

I did most of the work on my manual Taig micro-lathe. I did a few things differently than usual in order to increase efficiency. For instance I set up both a standard right hand tool in the front toolpost and a parting off tool in the back toolpost so I wouldn’t have to mess about changing tools twice per button.

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I made a couple of simple length gauges to control how much of the stock was protruding from the chuck at each stage, then turned up to the Z axis stop (set up to allow the carriage to almost touch the chuck). The short gauge is for the peg on the bottom of the button, and the long gauge is for the main body of the button. I also made full use of the graduations on the cross slide handwheel to produce the two diameters without stopping to measure the part.

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I made a special jig to hold the button while I drilled and countersunk the cross hole on both sides. It is built in such a way that you can turn it over 180 degrees and locate it using the two pins on the baseboard, which is clamped to the drill press table.

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Although this photo shows a standard jobber drill bit, I found it worked better to first use a smaller, more precise drill press to spot the hole location with a small centre drill, otherwise the bit drifts to one side or the other and you end up with an off-centre hole.buttons7

Finishing the top of the button involved facing off the parting-off stub, hand-sanding to round it off slightly, then flame polishing with a pencil torch to get a smooth glossy finish.

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(Close-up picture of the polished button didn’t come out well – it turns out that my camera’s autofocus struggles to lock onto glossy black objects!).

This video shows the whole process:

Here’s a finished button:buttons8

And the full batch (more than I need for the first instrument – I made extra because I wasn’t sure how many I would ruin in the process, and I can always use the extras for my second instrument):

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After completing the buttons, I now had prototypes of all the parts of a concertina action, so I decided to put it all together in a little test piece:

As well as the crude box itself, I made the pad, samper, grommet, lever, post, spring, felt washers, button, and both bushes. It is currently sitting on my desk as an executive toy, and I find myself reaching out and pressing the button whenever I’m thinking about a problem!

Update: After a couple of days of pressing the button whenever I happen to be at my desk, it definitely operates smoother and easier than when I first assembled it. I think the pad may be sealing more tightly too.

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Prototype Action Lever

I made a prototype action lever. It’s a Wheatstone-style riveted lever hand-cut from 1mm thick brass sheet (the post is 1.5mm; possibly a bit thicker than necessary, but I didn’t want it to distort when I hammered it in).

The hardest part was making a die tool to thread the pad end so that I could screw the leather grommet onto it. Because the lever is cut from thin flat sheet rather than round bar, an ordinary thread cutting die wouldn’t have worked, so I instead made a sprung die set to form the thread.

I started with a 15mm x 25mm x 100mm bar of O1 tool steel, drilled and filed a spring shape on one end, then slit it in half:

first_lever_2

Next I clamped it tightly together in a vice, and drilled and tapped an M2 hole in the middle of the slit, near the opposite end to the spring:
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I put a couple of M5 threaded holes in the bottom so I could bolt it to a chunk of angle iron, then hardened and tempered it to 200C, differentially tempering the spring end to a higher temperature with a blowtorch so it won’t break in use:
first_lever_6

After a bit of experimentation, I found that I could get it to form an acceptable thread if I cut a section of the 1mm sheet to 2.5mm wide (this dimension is fairly critical: 2mm forms almost no threads, and 3mm distorts and creases badly). It works best to hammer the tool fairly hard four times: once with the lever vertical, once each at 30 degrees from vertical in both directions, then a final time with the lever vertical again.
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The lever after sawing it out with a jeweller’s saw, forming the thread, and riveting it to the post:
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The proportions were based on one of the shortest levers in a treble English; most of the levers will have longer straight sections. The straight section is 2mm wide; I had to make the threaded part a bit wider (the tool squishes it narrower and thicker):
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After screwing the grommet on. It is necessary to enlarge the hole in the leather grommet to 1.65mm before it will screw on without using excessive force and damaging the grommet:
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Spring Winder

I made a simple machine for winding concertina springs, inspired by Bob Tedrow‘s video.


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It has a drum with a mandrel sized for the desired coil diameter and a hook on the outside, driven by a crank handle. The small step at the base of the mandrel helps to get the first turn of the coil tight. The adjustable guide plate isn’t strictly essential, but it helps a bit with consistency.

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The raw spring material; 22 S.W.G. (about 0.7mm) phosphor bronze spring wire. It bends easily, is fairly corrosion resistant, and I’m told it lasts a lot longer than brass. At some point I’m planning to experiment with stainless spring steel and other diameters, but I’m sure the phosphor bronze is going to work fine for my initial prototype instrument.

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Step 1; use needle nose pliers to bend a right-angle that will form the ‘pin’ that you push into the action board:

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Step 2; insert the wire into the machine as shown. It’s important that the hooked end is parallel to the face of the drum:

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Steps 3 and 4; turn the crank handle clockwise about 2 1/4 times, then cut the wire off, using the guide plate to gauge where to cut.

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Step 5; use small round nose pliers to form the hook:

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Step 6; use needle nose pliers to bend the hook over at a right angle:

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The finished spring:

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Here’s a quick video of the process:

Sometimes it’s necessary to use an opposite-hand spring because of limited space on the action board. You make these in the same way but doing all the bends the other way and turning the crank handle anticlockwise:

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A few experiments with various arm lengths:

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Punching Washers and Grommets

I decided I wanted to try making some punch tooling in order to manufacture a couple of the parts involved in a traditional concertina action: the felt washers that go under the buttons and the leather grommets that screw onto the ends of the action levers.

As well as the big Smart & Brown 2-ton toggle press mentioned previously, I also have a little 600N Brauer one (if my calculations are correct, the big one is rated to deliver about 30 times the force of the little one). I got it second hand some time ago, with some odd custom tooling attached to it that I never figured out what it was supposed to do. Here it is after removing the tooling and cleaning it up a little (yes, that is an old gear knob on the end of the handle – actually quite a nice addition so I left it on):

washerpunches1

Because the throat height of the press is considerably more than the thickness of a piece of felt or leather, I turned up a 50mm tall spacer block from scrap 1″ mild steel bar. It bolts to the table of the press and has an M8 threaded hole in the top for the punch anvil, and a cross hole for the ejection of waste punched through the hole in the middle of the anvil.

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I needed to cleanly bore out the inside of the felt washer punch, so I ground a simple D bit from the 1/4″ shank of a broken HSS end mill:

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I drilled most of the waste out first, then used the D bit to open it out to 1/4″ and cut a flat bottom on the hole. At this stage I also drilled a 1.5mm hole for the centre pin:

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I used the compound slide to turn the tapered sections of the top punches, stopping while the edge was still fairly blunt. After hardening and tempering, I put them back in the lathe and used emery paper to clean up the taper and sharpen the edge.

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Threading the other end of a punch with an M8 die so it can screw into the press arbor:

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The anvil and felt washer punch installed in the press. I made the half-nuts that are used to lock the tool at the desired height by facing ordinary full nuts on an arbor.

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Here’s a quick video clip showing the felt washer punch in use:

This shows where the washers go on the buttons, to stop them making a clacking noise when they bottom out:

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A nice stockpile of washers for my first few instruments. I made these from a sample piece of ‘baize’ woven wool cloth as used on gaming tables. I also have several other sample pieces in various different colours. I think the original washers may have been made from an actual fine, thin felt rather than a woven cloth, though – I need to get hold of some samples to experiment with.

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The first anvil I made had a design flaw: the hole through the middle for the ejection of waste material was drilled 1.5mm diameter all the way through the tool. In practise it quickly became constipated and I had to repeatedly remove it and drill out the waste. The one on the right is a second, improved version that is relieved to a larger diameter until a couple of mm from the top surface:

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Here are all the punches and anvils I made. The first one is the felt washer punch. Inside it is a couple of layers of spongy foam and then a couple of felt washers; with careful adjustment of the pressing force this seems to be just right to prevent the washers getting stuck inside. The second one I had optimistically hoped might work the same way, but the grommets just got stuck inside it and wouldn’t come out, so I instead decided to use it to punch out the centre hole and mark the location of the outside of the grommet, then switch to the third punch which has a slot milled in the side to allow the grommets to be pushed through and removed from the top.

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Here is a video clip showing the leather grommet punches in use. Note that in the video I was using 2.5mm veg tan cowskin, however I subsequently found that I got much better results from 4mm leather instead (the 2.5mm leather compressed down to 1.5mm in the punching process and the 4mm to about 3.2mm). I also removed the stripper plate seen in the video because I found it was getting in the way and causing more trouble than it was worth:

This shows where the leather grommets go inside the instrument. They screw onto the end of the lever arm (which is lightly threaded), then glue to the samper disc on top of the pad:

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A couple of hundred leather grommets for my first few instruments:

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Although these are fairly trivial parts, it certainly feels like progress to be stockpiling significant quantities of production-quality parts that I have made using my own tooling.

UPDATE: I’ve since got hold of some 0.8mm piano bushing cloth and punched more washers from it:

red_washers

The piano bushing cloth is thinner, finer, and more tightly woven than the baize. Unfortunately I’ve only been able to find it in bright red with a white core. I may experiment with dyeing some of it black.

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Reed Prototypes Part 1: Frame and Clamp

Recently I made my first prototype concertina reeds. There’s a lot to write about so I’m going to divide it into two articles, this one will cover the frames and clamps, and the next one will cover the tongues.

My plan was to make a drop-in replacement for one of the low ‘B’ reeds in my vintage Lachenal English. I think this instrument was probably one of Lachenal’s higher-end ‘broad scale’ models, because I also have another steel-reeded Lachenal that in many cases has narrower reed tongues in the same pitch. I’m not totally sure why the narrow scale models existed or were originally cheaper than the broad scale equivalent (the extra metal and labour is fairly trivial). They were probably quieter at the top end of the dynamic range, which might make them better for a student instrument.

I understand Wheatstone’s earliest reeds were made totally by hand, piercing them with a jewellers’ saw and cleaning them up with files. This must have been very labour-intensive, highly-skilled work, and prone to inconsistency. At some point fairly early on, perhaps when Louis Lachenal was hired to mechanise production(?), they changed to using fly-presses and dies to punch out the reed frames. This was much faster, worked well, and the presses could be operated by relatively unskilled workers, but the disadvantage is that precision dies are very expensive to make. To save on tooling costs, instead of making a different set of dies for every pitch of reed, they made do with a handful of sizes and made up for the gaps between them through careful tongue profiling. Until relatively recently, the need to invest in a set of press tooling was a significant barrier to entry for new reedmakers.

Enter CNC machining. I understand other makers have successfully used laser cutting or possibly wire EDM, but I have my own small CNC milling machine so that is the process I am going to use. It is fairly slow (certainly compared to a a press tool), but it works pretty well and I hope to get to the stage where I can load in enough brass for half an instrument worth of reed frames, and set it going with minimal supervision while I work on another task. As well as cutting out the shapes of the frames and clamps, it can also cut the vent slots (albeit with filleted corners), drill the clamp holes, engrave the note labels and a logo, counterbore the clamp screw holes, and even chamfer the top edges of the frame so they fit nicely into the dovetailed slots of the reed pan. Initially I’m planning to copy all the dimensions of my prototype reeds from the Lachenal instrument, but in future when I understand the design parameters better I will be able to make frames that are the optimal size for each pitch.

My first attempts at milling frames were using scrap aluminium. It took me quite a few failed attempts before I got one that seemed pretty good (the antique Lachenal frame I was copying is on the right):

aluminium_reed_attempts

Next I moved onto brass prototypes, immediately running into problems with it cutting very badly and breaking 1/16″ end mills:

failed_brass_reed_shoe

A microscope view of an end mill with clogged flutes, from a run that I aborted before it snapped:

clogged_end_mill

I think the reason for my problem was that the chips weren’t clearing from the slots properly so on subsequent passes they were getting re-cut and generating a lot of heat. I experimented with a lot of parameters, but basically what worked was making the depth of cut shallower, increasing the spindle speed to 10K RPM (the maximum my machine’s spindle can handle), significantly increasing the feed rate (to make bigger chips), and adding a compressed air blast to blow the chips away. I also changed from two flute HSS bits to three flute cobalt bits, though I’m not certain that helped with the chip clearance (it did allow me to increase the feed rate a bit more). It also proved necessary to make some proper mechanical clamps to hold the plate to the spoil board, because double-sided tape wasn’t holding it securely enough:

sheet_metal_mill_clamps

Here is a (21 minute long) video of the process of milling a single reed shoe prototype. Don’t bother watching the whole thing unless you’re really fascinated! This isn’t quite the final program: I subsequently altered the bevelling operation slightly so that the frame wedges more securely into the reed pan.

The CNC program includes small tabs that prevent the parts coming loose during machining. Afterwards these need to be manually cut. I found that it was possible to break them out with a small chisel but it left rough stubs that I then had to clean up with a file, so I changed to cutting them with a jeweller’s saw:

cutting_reed_frame_tabs

Because I cut the vents using a 1/16″ end mill, this leaves 1/32″ radius fillets in the corners, which should ideally be dead sharp. I’ve been manually cleaning these up using a fine square needle file with one edge ground smooth. I put the reed frame over the small square hole in my bench peg (see previous photo), hold the safe face of the file flat against the end of the vent, and carefully file sideways into the corner until it’s as sharp as possible without leaving a nick:

reed_vent_squaring

The clamp screws I’m using are a bit smaller than the originals; they are M1.6, stainless steel, with 2.5mm diameter allen heads:

clamp_screw_comparison

In my testing they are strong enough for the purpose and take up less space than the originals, and the finer pitch and allen heads make them easier to tighten and loosen without damaging them.

When tapping the clamp screw holes in the frame, it’s very important to keep the tap perpendicular to the hole. After researching tapping machines and complicated guides, I came up with this simple method that works surprisingly well (though I still managed to break a tap the first time I tried to tap one of the brass shoes!):

I added counterbores to the holes in the clamps because it was easy to do and significantly reduces the height of the reed without weakening the clamping ability. It also improves the accuracy of the location slightly. Because I was already using an engraving operation for the note labels, I added a simple brand to the clamp (HC=Holden Concertinas):

reed_clamp

Because the screws start out a couple of mm too long, I put them in the frame and grind them almost flush with the bottom of the frame, then finish them off with emery paper on a sheet of glass:

grinding_clamp_screws

One of the defining characteristics of traditional concertina reed shoes is that the underside of the vent is relieved (i.e. the bottom of the slot is slightly wider than the top). My current understanding is that this allows the reed to work properly even at very low bellows pressures, i.e. it enables you to play quietly if you want to. It also has an effect on the tone. I’m not doing this on the milling machine because there are good reasons to cut them out from the top and it would be a bit tricky to turn them over and accurately register them for an extra operation. Instead, I made a special jig that allows me to file the vent to a consistent angle using a flat needle file with two safe narrow edges.

The clamp part of the filing jig started out as an old war-surplus hand vice with damaged jaws:

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I trued up the jaws and modified the profile of the front jaw so that there is room for the file to tilt down below the level of the back jaw:

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Next I added an adjustable brass frame and a PTFE roller to guide the file, as shown in the following video. I align the top edge of the vent with the top of the back jaw, paint the inside of the vent with a black marker pen, and file until I’ve almost but not quite removed all the ink.

Here we have my first brass reed frame in my Lachenal reed pan. You can see how much lower-profile the new screw heads are: I think this might help with air flow inside the reed chambers. It took several prototypes before I was totally happy with the tightness of the fit in the dovetailed slot. There is a small area around the clamp that isn’t fully bevelled, giving a nice friction fit without compressing the sides of the frame adjacent to the vent.

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finished_brass_reed_frame

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