Work in progress

Not Dead Yet

The blog has been quiet for a while because I’ve been very busy over the summer with non-concertina-related projects, but as autumn draws in things are starting to get more interesting here. I’ve got a third earring design on the drawing board, my CNC milling machine is nearly ready to make its first cut, and I’m in discussions with a client about developing a couple of exciting new instruments.

Yesterday I got a bigger external monitor so that I can fit a lot more on the screen at once when I’m doing CAD/illustration work. Designing the bellpush fretwork on a 13″ laptop screen was an experience that I’d prefer not to repeat!
design_station
The design on the screen is the logo for a side project I’ve been working on in my spare time for the past couple of months. It’s a piece of software called Handwheel for sending instructions to my milling machine. More on that in due course!

More Earrings

I’ve been commissioned to make another couple of pairs of the hexagonal English earrings. Here are some photos from this afternoon’s work drilling and cutting.

I’m still drilling manually using the Taig mill. I used a 1.2mm bit for the button holes, a 0.9mm bit for most of the piercings, and a 0.7mm bit for the tiniest piercings. All re-sharpened PCB drilling solid carbide bits, and for a change I didn’t break any!

earring_making_1

Lots of silver swarf. Unfortunately it’s not very practical to collect it, though I do keep the scrap from the piercings. One day I may have enough to melt down and cast them into something useful!earring_making_2

The saw blade has to be unclamped and threaded into each piercing in turn. The teeth are too fine to easily see so you have to figure out which way to put it in the frame by running your finger along it. The wing nut is used to set the tension.earring_making_3

In this picture you can see my new bench peg clamped to the crossbar of a builder’s trestle stand. I like to work standing up with the saw table quite high so that I can get my eyes close to the template without needing to bend over, which would hurt my back after a while.earring_making_4

After a lot of frustration with paper templates that inevitably came unstuck or became illegible, I think I’ve finally found a template material that works reasonably well for very fine metal piercing: inkjet-printable matte white self-adhesive vinyl film. It’s not cheap but then you don’t need much of it for a pair of earrings, and if it enables me to produce a better end product with fewer headaches then it was well worth it!earring_making_5

Thanks to Juliet for the photos of me working. ūüôā

 

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

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 Рthis 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.