The stepper motors have arrived that I’m going to use to convert my Taig Micro-Mill to CNC.

It’s hard to explain how exciting this is. I’ve dreamed of owning a CNC machine tool for probably twenty years and yet somehow never got around to building one. I bought the Taig about a decade ago for another project with the intention of fitting it with DC motors and encoders and building my own servo controllers (in hindsight that was a bit of a silly idea considering steppers are relatively cheap and work OK on a machine as small as the Taig). I got as far as buying the motors, encoders, pulleys and toothed belts, and a large block of aluminium that I was going to machine the mountings from, before the project ground to a halt. There are some photos on my old website of the mill when I first received it. I have used it occasionally as a manual mill but what I really want is to be able to use it to machine complicated parts under automatic control.

The motors are bigger than I expected, and I went for the small end of the range people tend to put on this machine. There are a couple of different theories on stepper motor sizing for the Taig mill: 1. use small motors and keep everything well adjusted and lubricated so you don’t need lots of torque. 2. use big motors so you have lots of torque in reserve and it doesn’t matter so much if the leadscrews and slides get a bit stiff. The advantage of the smaller motor option, as well as lower cost (both in terms of the motors and the electronics to drive them), weight, power consumption, and heat generated, is that smaller motors have lower winding inductance and armature mass. Lower inductance means the torque doesn’t drop off as rapidly as the speed increases; lower mass means they can accelerate and decelerate quicker. I’ve read people advocating both paths and claiming to get better results with small/large stepper motors, but the smaller, nimbler option appealed to my sensibilities more (as somebody who is happy driving a small, light car with a 48Bhp engine).

Here’s another lovely vintage tool; one that almost certainly will get used in my concertina production. It’s a small Swiss-made bench shear of a design that I have never seen before. One of the blades is a helical shape (that must have been pretty tricky to make!), and as you rotate it the shearing point slides along the fixed straight blade. The maker’s stamp appears to say ‘Clico’ but other than that I know very little about it. It’s quite small and very precisely made; I suspect it was probably intended for jewellery or clockmaking. It was a little bit pricey for a second hand tool (about the same as a new Chinese-made bench shear of more conventional design), but it’s such a lovely thing and works so well that I regard it as a bargain. As long as I don’t abuse it and hone the edges occasionally, it should outlast me. When I got it the blades were quite blunt but it still cut surprisingly well. I sharpened them last night and it now cuts really cleanly with more control and much less effort than a pair of hand shears.

The state the edges were in before sharpening:

The unclear maker’s stamp. I think it says “Clico”. The number doesn’t seem to refer to a patent (too short). Perhaps it is a serial number.

A brief video showing how it works (I would normally use two hands but one was holding the camera):

I love old well-made tools. Recently I picked up a vintage Moore & Wright spirit blowpipe (I thought they only made measuring tools!). It’s a very nicely made brass wick burner with a pipe that allows you to blow a stream of air across the flame. This creates a very hot, concentrated flame that can be used for hard soldering. I may not actually use it in concertina production (I have several modern gas torches than are more convenient and powerful), but I thought readers might be interested to see it.

I haven’t quite got the hang of it yet; it’s much trickier to use than a gas torch. It also doesn’t seem to produce much heat. I suspect it would work much better on a jeweller’s charcoal soldering block because then any excess oxygen in the stream would make the charcoal burn and generate extra heat. I tried it with a piece of ordinary barbecue charcoal but it crackled and spat sparks at my face so I quickly gave up! I also suspect the meths I’m using may be too dilute to produce a really hot flame.

Here’s a video of me experimenting with it. As you can see the brass got hot enough to anneal it but I doubt it was hot enough for silver soldering.

Update: I spent a while this afternoon practising with the blowpipe and successfully made several silver-soldered brass joints on the refractory brick in the video above. The key seems to be to blow very lightly and consistently (using circular breathing technique) in subdued lighting so you can see the parts of the flame clearly, and at all costs don’t let the blue inner cone dwell on the work. It is far colder than the outer flame. It also helped to push out a bit more wick to get a slightly larger flame. The job took longer than it would have with a cheap butane gas pencil torch, but I got there in the end.