Month: March 2015

More Earrings

I just finished off some more earring orders. It was nice to get an order for the octagonal Anglo design; it is a more intricate design than the English and I don’t think I entirely did justice to it when I made the prototype. My tools, processes and skill with the piercing saw have all improved in the past few months and I’m pretty pleased with how the new pair turned out.

The inkjet-printable self-adhesive vinyl templates are working out great, particularly after fiddling with the printer settings to get them as sharp as possible. I’ve also tweaked the designs a bit to improve the drill targets.

Lots of holes to drill in the Anglo design. Quite a few of them need to be 0.7mm diameter because the piercing isn’t wide enough for a 0.9mm drill (I avoid using the smaller size for everything because they are extremely delicate):


Nice sharp lines on the template really help you to get accurate saw cuts. I do all the piercing with Vallorbe 8/0 blades, the smallest size I can easily obtain.

The finished Anglo earrings:

Somebody commented recently that the pictures on the earlier post make the Anglo design look much bigger than the English. In fact they are very similar in size, though perhaps the Anglo looks more substantial because the piercings are mostly smaller:

Star Punch

I made an eight-pointed star punch today for decorating an item of silver jewellery that I have been commissioned to make. Although it is not directly related to concertina-making, I thought it might make an interesting article for the blog anyway.

I made the punch from silver steel, which is a high-carbon tool steel with some chromium in it that comes as precisely-ground round bar stock in a range of standard diameters. It’s pre-annealed so it’s pretty easy to work with hand tools and machines before hardening. The bar I happened to have in stock was 3/8″ diameter.

I started by grinding a double-angled cone on the end:

Then I filed the facets of the punch using square and triangular jewellers’ files under magnification and plenty of light, resting the punch in a corner of my bench peg.

I must admit this took me two attempts. The first time I completely messed up the relief angles (it produced a circle of eight triangles with no centre), so I had to file it back to a blank cone and start again!

I lightly punched  a piece of softwood to check how it looked prior to hardening:

I didn’t want to have to try to grind firescale off the working end of the punch after hardening, so I coated it in a thick paste made from a stick of chalk mixed with a drop of water. The idea is that it prevents oxygen getting to the surface of the steel so it doesn’t corrode despite the extreme heat. My research on what substance to use for this purpose turned up a wide range of possibilities from specially-formulated industrial coatings through cockroach poison (boric acid) to something that sounded like a recipe for white bread. I had some chalk on hand and I saw it recommended in more than one place, so I thought it was worth a try.


It wasn’t worth firing up the forge for such a small job, so I simply placed the punch in a (metal) bucket of dry coke and hit it with a propane torch. The coke quickly heats up and reflects heat back at the work.


Here’s where I made my second mistake. In the heat of the moment (literally) I forgot that you are supposed to quench the tool by lowering it gently into the water tip-first so as to minimise stress and risk of cracking. Instead I thought “must cool it as quickly as possible,” grabbed it with the tongs, and randomly dunked it into the bucket side-on. This resulted in a crack along the length of the shank, luckily not reaching all the way to either end.

I tempered it by heating the shank in a spirit flame until the straw colour reached the sharp end. This differential tempering makes the end you hit with a hammer much softer and tougher than the end that cuts into the work, which is a desirable quality in a punch.

The finished punch. The anti-scale chalk paste did a reasonable job I think; all I did after hardening was to clean it off with a wire brush:

Here you can see the crack most of the way along the shank. The tool seems to be working OK regardless though:

Finally, the proof of the punch is in the marks it makes. I haven’t tried it on silver yet, this is a piece of scrap aluminium. I rather like the slight unevenness of the points, and it’s nice how you can vary the size of the star by the strength of the hammer blow:

Glue Pot

I’m a fan of hot hide glue for musical instrument work. There’s no need to rehash the pros and cons of HHG versus liquid hide glue and modern synthetic glues like PVA; suffice it to say that it has been used successfully for millennia and I think there are very good reasons to continue using it for certain things including high-quality instruments.

To use HHG, you first dissolve it in water to make a gel, then heat it to about 60C (140F) to melt it. Too cold and the open time is reduced; too hot and it ‘cooks’, compromising the strength of the glue joint. Traditionally cast iron or brass double-boilers were used on a stove, an alcohol burner, or a charcoal brazier. Around the turn of the previous century somebody invented an electric glue pot, which used a thermostat and a heating element to maintain the correct temperature with much less fuss and risk of overheating the glue.

I know of two manufacturers still making electric glue pots. Hold Heet in the USA makes fairly large pots that are probably best suited for antique and reproduction furniture work. Herdim in Germany make smaller pots that seem to be targeted mainly at luthiers. From my research it seems that the Hold Heet pots are expensive in the US and very expensive in Europe, while the Herdim pots are expensive in Europe and very expensive in the US. Second hand electric glue pots of either brand never seem to come up on eBay in the UK, and it wouldn’t have made financial sense to import a used Hold Heet from the US and buy a 240V-110V transformer to power it. I strongly considered buying a new Herdim, and if money was no object that’s probably what I would have done.

If you search Google for alternatives to commercial electric glue pots, people have made them from various kinds of electric coffee pots, baby bottle warmers, old cast iron glue pots on electric hotplates, etc.

My new one is made from a mini deep fat fryer (0.5 litre oil capacity). I wasn’t happy with its built-in mechanical thermostat (it had about 15C of hysteresis and would probably have needed frequent adjustment), so I have instead hooked it up to a cheap Chinese PID temperature controller (a Rex C100 clone) with solid state relay output. This works remarkably well, regulating the temperature of the water bath to within a degree of the set temperature by pulsing a little bit of power into the heating element about once a second. I found I needed to set the water bath temperature several degrees higher than the desired glue temperature.


I knocked together a simple wooden box to hold the controller and the SSR, and a Perspex cover to hold the inner pot in position and prevent the water in the outer bath evaporating away. The light blue gaskets are made from two-part mouldable silicone rubber. The inner pot is a 0.25 litre Stewart Sealfresh screw-top food container. I have several of them and I cut a brush-sized hole in one of the lids to reduce the rate at which water evaporates from the glue in the pot.

I also made several glue brushes in various sizes by whittling the handles from green wood and binding hog bristles to them with string. The smallest brush I made by boiling the end of the stick in water for five minutes, then smashing the fibres apart with a hammer: