Schärf-Fix 2000

This was my Christmas present to myself.

scharffix1

scharffix2

scharffix3

It is a Schärf-Fix 2000 manual leather paring machine made by Teknomek HB in Sweden. I think the name means something like quick-sharp in German (presumably the model number ‘2000’ was chosen because it sounded futuristic when they were developing it!). It is used for easily and consistently thinning down leather in three different modes.

It is primarily intended for traditional bookbinders who cover books with leather, but it turns out that the construction of English-style concertina bellows has a lot in common with bookbinding. They are nicely designed and well-made machines but they are very expensive new, are highly sought-after by hobbyist bookbinders, and AFAIK no other manufacturers currently make a similar machine. I had to wait about a year for a second hand one to come up for sale on eBay. My backup plan had been to build my own by adding a roller and an adjustable blade holder to the frame of an old sewing machine.

The first operation mode is skiving. You turn the top knob to tilt the blade relative to the roller so that when you pull a piece of leather through it, it thins the edge of the piece to almost nothing at a shallow taper angle:

scharffix4

The reason for skiving edges is so you can glue one piece on top of another without a step, both for cosmetic reasons and so there isn’t an exposed edge to catch on things and come loose. This is what an overlapping joint might look like without any skiving:scharffix5

And this is the same two pieces of leather but with the edges of both top and bottom pieces skived so the tapers match up. Looking at the vintage concertina bellows I have, joints made this way tend to be almost invisible. Unlike a butt joint, a skived overlap joint is air-tight and nearly as strong as the original leather:scharffix6

The machine’s second mode is splitting: if you set the blade parallel to the roller it will pare the leather down to a controlled thickness. Although it can only pare strips 30mm wide, it’s possible to do wider pieces using multiple passes. There are two main reasons to split leather: to make it more flexible, and to compensate for variations in thickness in different parts of a hide. This photo shows a piece I split down to the sort of thickness that I think is normally used in bellows construction:

scharffix7

The third mode of operation is probably not very useful for concertina making. You can replace the standard parallel roller with one that has a raised portion and set the blade parallel, so it cuts a furrow out of the middle of a piece of leather, forming a more flexible area. I think bookbinders use this technique at the hinges of a book.scharffix8

0
Facebooktwittermail

Belgian Blue Whetstone

I like to sharpen my cutting tools, particularly the ones I use for wood carving. Actually that’s not entirely accurate; I prefer to carve with tools that are extremely sharp, which meant I had to learn how to sharpen them. I also often sharpen cooking knives, axes, chisels, hand plane irons, scissors, and for the concertina work I’ll need to be able to put a really good edge on leather skiving knives and possibly gravers.

Until now what I have tended to do is to sharpen tools on a fine India oilstone, which leaves a sharp but slightly rough edge, and then hone/polish them using a rotary electric polishing machine. That does sort of work, but because the wheel is flexible it tends to round off the edge at a microscopic level, dulling it slightly in the process. I recently went looking for a better solution and, after a lot of research, decided I liked the sound of the Belgian Blue whetstone. A letter was written to Santa Claus my parents, and as a result I found one in my Christmas stocking.

The Belgian Blue is a natural abrasive stone that is similar to, and found right next to, the famous Ardennes Coticule. It is less aggressive than the coticule, but it apparently produces practically the same finish and because it is much more abundant and found in larger pieces it is merely quite expensive rather than astonishingly expensive. It is a pretty purplish slate with red mottling:

bluestone1

 

You can’t really see it in the photo, but it glitters subtly. This is because embedded throughout the slate are millions of microscopic garnets, which are very hard crystals. You can simply wet the surface of the stone and rub your knife on it in the usual way and it will slowly polish the metal, though it is much more effective if you first rub the smaller stone (known as a slurry stone) over the surface, which generates a pinkish abrasive slurry:

bluestone2

The Belgian Blue isn’t aggressive enough to sharpen a blunt edge in a reasonable timescale. You need something coarser to do that. What it’s good for is going from a rough but sharp edge to the next level: a smooth, shaving-sharp edge:bluestone3It should also be good for touching up edges that have gone a bit dull (too much to fix by simply stropping on leather) but aren’t damaged or blunt enough to need a lot of metal removing with a coarser stone.

 

0
Facebooktwittermail

Pretty Punches

My best friend, Juliet, gave me a set of New Old Stock hand-cut 1/8″ number punches for Christmas. I plan to use them to stamp the serial numbers in all the instruments I make.
prettypunches1

The astute among you may have noticed that there is no number 9 punch – that is because you are intended to use an upside-down number 6 instead! The bottom line in the photo was my first attempt, punching into soft aluminium sheet on a block of wood; the metal deformed quite a lot so I tried again on an anvil and got much better definition.

Although it is possible to buy good quality brand new number punches, I believe they are now all cut by CNC machines and they look quite different. Being something of a traditionalist, I like the fact that they were hand-made, and it’s great that she managed to find a set in perfect un-worn condition. I’ve done a bit of research into how this kind of punch was made because at some point I want to cut a punch of my maker’s mark.

prettypunches2Taking the above No. 4 as an example. First they would have annealed a small piece of high carbon tool steel bar and filed the end into a triangular pyramid shape, then hardened and tempered it and polished it smooth. This tool is known as a counterpunch and could be re-used many times (perhaps occasionally dressing it on a fine stone if the corners get a bit rounded). Sometimes one counterpunch could be used for more than one character (e.g. ‘P’ and ‘R’).

Secondly they would forge another, larger, piece of tool steel into the shape of a punch blank and anneal it, then they would file and polish the end flat, square and smooth. They may have transferred the design onto it at this point, or more likely a skilled punch-maker would have just worked by eye.

Thirdly they would use the aforementioned counterpunch to punch the counter(!), which is the enclosed triangular space.

Fourthly they would use a small triangular file to cut away the metal around the outside of the lines, leaving a very narrow rounded top edge. The angle of taper is fairly important to get right so the tool cuts sharply-defined characters but doesn’t wear out quickly. On my punches they seem to have used a coarse file to remove most of the metal at a steep angle, then switched to a very fine file at a blunter angle in the last couple of mm.

Fifthly they would coat the point of the tool in something to protect it from firescale and then they would harden and temper it. They would use differential tempering to get a hard tip and a tough hammer-resistant shaft by heating the blunt end and watching the colours run up the shaft, then quenching it when the right colour reaches the point. I’ve seen a film of somebody using a pot of molten lead to do this in a very controllable way, though of course a skilled toolmaker can produce just as good results with a coal forge.

 

0
Facebooktwittermail

Concertina Earrings

Here are a couple of Christmas presents I made for my nieces: hand cut concertina-shaped silver earrings.

The first pair is a hexagonal 18 button English, 19mm across flats. The layout goes from G up to C and includes two sharps and three flats (copied from the layout of a real 18 button semi-miniature).earrings1

The second pair is an octagonal 20+1 button Anglo, 20mm across flats.

earrings2

My original plans included soldering on buttons and handrests, and engraving my maker’s mark onto the ovals, but the fretwork took far longer than expected and I ran out of time (I finished polishing them at 8PM on Christmas eve!). I didn’t realise until it was time to drill the piercing holes that the design I came up with for the anglo is much fiddlier than the English – lots of very small piercings.

What’s that you ask? Why yes, I do take commissions. There’s still plenty of time before Valentine’s day. 😉

Update: I have got a bit better at making these with practice. See the photos on this entry.

0
Facebooktwittermail

Manual Mill

It took more than a day’s work to dismantle, clean, reassemble and adjust the Taig mill. Funny how sometimes you don’t realise just how filthy a thing is until you start scrubbing the layers of grime off it (in this case, dried oil and grease with swarf and dust embedded in it):

mill1

Shiny clean parts ready for reassembly:

mill2

I also replaced the leadscrew bearings in the Y axis because they had gone rather lumpy. I’ll probably do the other two axes as well soon.

mill3

Reassembled mill, bolted to an offcut of kitchen worktop and ready to start a precision drilling job.

mill4

I need to drill about 120 holes, precisely located by eye (under magnification), 1mm dia or less in 1.5mm thick sterling silver. Annoyingly I broke two expensive Swiss 0.7mm HSS bits within the first few holes (not entirely sure why – it doesn’t help that you have no feel at all for how much torque you are applying). I am now using a 0.9mm carbide PCB drilling bit (which is bigger than I would prefer), and have successfully made it through about 40 holes by peck drilling and feeding very slowly indeed. I’m probably spending about a minute on each hole. CNC would certainly make the job easier, even if I was only using it to manually jog to each hole location before running a few lines of code to automatically drill the hole at a consistent feed rate.

0
Facebooktwittermail

Mucky Mill

I’m back at my parents’ house for Christmas, and while I’m here I’m hoping to make a start on converting my Taig benchtop milling machine to CNC. It has been stored under a sheet of plastic in a damp shed since I moved out of my previous workshop about five years ago (crikey, has it really been that long?). Fortunately I smothered everything in oil at the time, so it hasn’t suffered too badly from rust – the worst bits are the handles, which I’ll be replacing with motors anyway. The oil has gone sticky and attracted a lot of dirt though, so my first task is going to be to completely dismantle, clean, oil, remantle (is that a word? if not, why not?), and adjust everything to run smoothly and accurately again. I have a little job coming up where a manual precision drilling machine would be very useful so I’m planning to do the first stage quite soon.

mucky_millThe thing on the spindle is a first generation HighTechSystems rapid tool changer. Unfortunately it’s now discontinued, though I already have a decent selection of holders for it and I think once I have converted my Taig lathe to CNC it shouldn’t be difficult to machine bespoke ones to hold different sizes of tool. The idea is you have a specific holder for each tool used in a job. You set up in advance a software table that tells the machine controller exactly how far each tool sticks out of its holder, so you don’t have to waste time re-zeroing it each time you change tools (which is a manual process but only takes a couple of seconds).

 

 

0
Facebooktwittermail

Bellpush For Sale

I’ve finished the bellpush and put it up for sale on eBay.

All the previous posts about the project are here.

Specifications

  • 2″ (51mm) wide, 2 ¼” (57mm) tall, 1 3/8″ (35mm) deep.
  • Hand cut stainless steel front plate.
  • Light green glow-in-the-dark vinyl membrane behind the fretwork.
  • Stainless steel button and front plate screws.
  • Varnished oak backing box.
  • Brass electrical screw terminals.
  • Heavy duty sterling silver contacts, suitable for electromagnetic bells.

finished_bell_push_1

finished_bell_push_2

0
Facebooktwittermail

Bellpush Final Details

The bellpush is almost finished. It just needs another two or three coats of exterior varnish, then I’ll put it up for sale (haven’t decided how yet – probably an eBay auction). Here are pictures of a few of the final details.

Deeply countersunk holes for three mounting screws (I thought two might be a little wobbly if the wall/door isn’t completely flat, particularly as there wasn’t room to space the screws evenly):

bellpush_details1

My maker’s mark carved on the back. This is a different thing to the Holden Concertinas logo (which isn’t on the bell push because I haven’t designed it yet). The HC logo will be the company brand and will be externally visible; my maker’s mark is my personal signature and is usually hidden away somewhere (I put it on most other things I make too).

bellpush_details2

A brass serial number plate (visible when you remove the top plate), rather crudely stamped with a worn set of letter punches. The letters stand for “Holden Concertinas Bell Push 1”. Also seen in this picture is a little drain slot so any rainwater that leaks into the switch recess can run out of the bottom.

First coat of exterior clear varnish (thinned down so it soaks into the grain), after sanding the bellows valleys because the bottoms of the trenches were a bit fluffy. The grain of the plain oak looks really pretty. I debated with myself for quite a while over whether to stain it darker to look more like a vintage rosewood concertina. In the end, after staining and varnishing a test piece, I decided against it because it looked a bit fake and the end grain stained much darker than the side grain.

bellpush_details4

0
Facebooktwittermail

Fiddly Fretwork

Because I made the bellpush fretwork before I started this blog, I thought I would take a step back and write a bit about how I did it. Here’s a picture of the finished item (remember it’s only 50mm wide):

Bell Push Top

What I didn’t do was to design it 1:1 with paper and a pencil. Given my limited artistic ability and the level of fine detail involved, using computer aided design software saved me a lot of time and almost certainly led to a better end result. I could zoom in and out, automatically turn wonky hand-drawn curves into nice smooth ones, repeatedly draw and erase (without leaving smudgy marks each time), undo, redo, tweak, retweak, and basically fiddle with the design for hours on end until I felt it was good enough to hit ‘print’. That’s my little secret: I’m not very good at freehand drawing (I wish I was), but if you’re patient enough CAD lets you keep on making hundreds of tiny incremental improvements until you finish up with something that looks pretty good. In theory also I could go from a vector drawing to a control program for a CNC tool like a laser cutter, which is something I want to try in the future, though this project was about learning to cut an end by hand.

The software I used is an open source vector drawing program called Inkscape. I’m using a snapshot of the current development version for two reasons: it has a couple of whizzy new features that make it easier to do this kind of design, and it finally runs natively on Mac OS X rather than via the rather clunky X11 interface. The two new features are both path effects: spiro spline and power stroke (stupid name). Spiro spline basically makes it easy to draw really smooth curves. Power stroke lets you draw variable width lines (you can later convert a power stroke into an outline path – i.e. two curves that define the edges of the power stroke line; unfortunately that’s a one-way conversion). Rather than me spend a few hundred words attempting to explain more clearly why the combination of these two features is really useful for drawing the scrolly shapes you find in a Victorian-style concertina end, take a look at this video. (Incidentally, he would have been better off using the Path->Union command at the end to combine multiple powerstrokes into a single path.)

It took me three attempts to come up with a design I was happy with. Here are the three versions side by side:

top1 top2 top3

I spent a lot of time studying pictures of vintage concertina ends between attempts 2 and 3: I could tell my version looked wrong but it took a lot of analysis before I figured out exactly why and how to fix it. Something you might notice if you look closely is that in the first two the right and left hand sides are almost exact mirror images of each other. In the third one there are many very small differences between the two sides – this asymmetry, I found, makes the design look far more organic.

If you carefully compare the final design to the photo above, you’ll spot where I made a mistake with the saw in one place. I carefully tweaked the design to work around the mistake and it almost looks like I did it on purpose now!

Hand piercing a stainless steel concertina-style bell push

I cut the end by hand with a jeweller’s piercing saw, following a paper template glued to a piece of 1mm stainless steel. I used stainless because the bell push needs to be weather resistant – metal concertina ends are more commonly made of nickel-silver AKA German silver, which is actually a type of brass and is much easier to cut, though it would quickly tarnish outdoors. The biggest mistake I made was putting wax polish on the paper – I thought it would lubricate the saw blade and save me having to keep manually waxing the blade. Bad idea. The sawing generated a very fine black dust which stuck to the waxy paper and smudged it so badly that eventually I couldn’t see the lines clearly (hence the mistake mentioned above, caused by carrying on cutting where I thought there was supposed to be a line). After that mistake I printed out and glued a new template on top of the smudged one – very tricky to get the two perfectly registered – but then I had lots of problems with the bottom, waxy layer coming unstuck from the metal when I was cutting the points of the scrolls, hence why many of the points are slightly misshapen.

halfway

Another problem I ran into was blunting and breaking 1mm drill bits because I centre-punched where I wanted the holes to go, which work-hardened the stainless enough to cause my HSS drill bits to rub and go blunt instead of cutting. I switched to solid carbide bits (actually re-sharpened PCB drilling bits from eBay, which are good and surprisingly cheap). They cut through the work-hardened stainless OK, but I broke several of them because they tend to snatch as they break through the back of the work. Carbide is so brittle and delicate that the bits just instantly snap when that happens. In hindsight a better solution might be: a. mark the drill points using a centre drill or a tri-cornered centre punch and a very light tap to avoid work hardening the material, b. drill on top of a sacrificial piece of brass or aluminium to reduce the likelihood of snatching on break-through. I could also try using good quality cobalt bits instead of carbide.

The final problem I encountered was that of blunting and breaking jeweller’s saw blades. I must have gone through two or three dozen of them. I’m talking about very fine blades here – the teeth are so small that you can barely see them with the naked eye. They need to be small so you can cut the tiny details and tight curves inside the piercings. I started out using a highly-regarded brand that I have had success with in the past when cutting silver and brass, but they turned out to be not hard enough for stainless – they tend to go dull in one or two strokes. I found another brand that stays usably sharp for a bit longer (perhaps two piercings), but it’s still extremely easy to snag the blade in the cut and snap them because they are so tiny and delicate. It’s also very hard to follow a line closely with a dull blade because it tends to want to drift off in one direction or the other depending on which side happens to be sharper. One trick I might try in future is cutting out the bulk of each piercing out with a thicker, more robust blade, then going back later and doing the inner points and other details with a fine blade.

0
Facebooktwittermail

Pint-size Printing Press

Here is my new toy essential concertina-making workshop tool (mug of tea is for scale):

adana1

adana2

It’s a little Adana High-Speed No.1 (also known as a HS1 or 3×2)  self-inking platen printing press, possibly dating back to the 1930s. I plan to use it to print decorative bellows papers and maker’s labels, and possibly also stationery and marketing materials – compliments slips, business cards, bookmarks, beer mats, etc. I could perhaps even take a few small commissions as a sideline (wedding invitations and the like!). The maximum size of forme you can fit in the bed is 3 3/4″ x 2 5/16″ (95 x 59mm), though obviously the paper can be a little bigger than that if the design has margins around the edge. I got it cheap because it looks a bit tatty and it’s missing several parts, many of which are no longer made.

Some of you are probably wondering at this point, “why bother?” I much prefer the appearance of Letterpress printing over modern laser or offset printing because the type makes a 3D impression in the paper (you can also use proper metallic gold or silver ink, which you can’t do with a laser). It’s almost certainly also the method that was used on original Victorian concertinas. Although there are still a handful of commercial letterpress printers around who would probably be willing to print my designs for a fee, I want to do the printing myself on a machine in my own workshop with plates I’ve designed and made myself, for the same reasons that I’m planning to make all the other parts of the concertina myself.

Luckily you can download the original user manual for free. It is ‘arrestingly written in a non-technical style.’

printing_made_easy

From these instructions I gather the way you use it is to place an arrangement of (missing) movable metal type and furniture called a forme in a (missing) chase or clamp it directly into the bed, use a (missing) hand roller to transfer some ink onto the (missing) inking disk, then move the handle most of the way down and back up to pick up some ink on the (missing) pair of inking rollers and transfer it onto the face of the type. Next you place your piece of paper or card on the (missing) tympan (which is held to the platen by the (missing) tympan clips), lining the bottom edge up against the (missing) lay gauge. Finally you push the handle all the way down to press the paper onto the type. When you release the handle the (missing) spring-loaded gripper finger pulls the paper off the type.

adana3

I’m not bothered about the fact that it didn’t come with any metal type, furniture, chases, quoins, etc. because I’m instead planning to make my own printing plates after designing them on a computer. I have a few different ideas for ways to make the plates. The most obvious one is to use sheets of photo-sensitive polymer that are designed for the purpose (I already have a UV exposure box for PCB photo-etching); the main drawback with them seems to be that they aren’t super robust and they have a limited shelf life; perhaps a few years at best. For one-off print runs that would be fine. I suppose it wouldn’t be too much of a hardship to make new polymer plates every couple of years.

Alternatively I could use the same techniques that I use for PCB etching to make etched brass printing plates (using spray-on photo-resist). If I can get that to work and produce clean sharp edges, brass is hard enough that the plates ought to last pretty much forever as long as I don’t abuse them. Another idea I’m considering is to cut brass or aluminium plates on the CNC milling machine with a small vee engraving bit. That ought to produce excellent clean results, although it would probably be quite a slow process and any sharp internal corners might require cutting by hand with a fine graver. It might not be trivial to convert the design into G-code either. I’ve even considered using the mill to engrave a positive “matrix” into a piece of aluminium and use that to cast plates in type metal. One potential advantage of this method is I could mill a single matrix for a bellows paper or logo design and then cast as many copies of it as will fit into the bed of the press.

I’ve had to buy a new pair of inking rollers because, although I probably could have made the mechanical parts, I don’t have any practical way of casting the special soft rubber compound onto them. Luckily they are still made, though a pair cost me more than I paid for the entire machine!

I’ve also ordered a cheap soft rubber hand roller made by “Speedball” (isn’t that slang for an illegal substance?) to ‘mill’ the ink (work it until it’s totally smooth) on a sheet of glass and transfer it to the inking disk.

The inking disk shouldn’t be too hard to make. I’m planning to cut it from 3mm engraver’s brass sheet with a scroll saw, round off the edges, and braze a steel hub to the bottom. I haven’t yet decided how to make the ratchet on the bottom that rotates it to evenly distribute the ink, but I have a couple of ideas. The simplest way seems to be a circle of holes drilled in another disk soldered/glued to the bottom. The point of the pawl is a bit worn, but interestingly it looks like it was made to be reversible when the first point wears out:

adana4

The tympan clips will be trivial to make from stainless steel sheet. The tympan/packing is a bit of mystery to me – it would probably be easy to make if I knew exactly what to make it from (it seems to be some combination of card and paper). The purpose of it is to provide a soft surface between the paper and the platen so that the type makes a visible impression in the paper and isn’t damaged by being forced hard against the metal platen. More research and probably experimentation needed.

The lay gauge will probably not be too difficult to make from a strip of brass or aluminium and some small screws and wing nuts, though I don’t fully understand the illustrations of it in the manual – it has various cutouts and holes in it that I haven’t yet worked out the purpose of.

The most difficult replacement part to make looks like being the gripper arm and gripper finger. This is the part that holds the paper against the tympan so that when you release the handle the paper doesn’t remain stuck to the type (if it did, the inking rollers would probably run over the back of it before you had a chance to manually remove it). It needs to be adjustable for different sizes and thicknesses of paper and there needs to be a long spring so it can easily be lifted up to replace the paper. I’ll also need to track down a nut that fits the shaft so that I can attach it to the machine (almost certainly won’t be metric; possibly 2BA or similar).

0
Facebooktwittermail