2023-12-23

Last modified: 2023-12-23 15:52:05

Thin barrel

So the plan is to try and make a thin barrel, and then wind a mainspring with it.

The barrel will have a gap in the perimeter to permit winding up the mainspring, and also a small drilled hole to hook the end through.

I want to make a ~50mm barrel out of 1mm brass, using a large superglue arbor to drill the centre hole and machine away the ~0.3mm depth for the spring to fit in.

Here's a big superglue arbor:

The big disc is from an offcut from the lawnmower hubs. The shaft is glued in with Loctite 603, it was a very close running fit, which is I think exactly what is required.

Next up, cut out a piece of brass to glue onto it to make the 50mm barrel.

Come to think of it, maybe Loctite on a superglue arbor is a bad idea, because the Loctite will let go when it is heated to free the superglue. May need to fix it some other way.

After facing off the join is almost invisible:

I'm not really convinced by how well the brass is glued:

I think I need a better way to spread the pressure when clamping it. I used a small-ish rod in the tailstock chuck, pressed up against the aluminium die block, pressed against the brass. But maybe need something flatter.

Seems to be working!

This brass seems different to the rod stock, the chips are long and stringy and brighter in colour. It turns more like aluminium.

Great success, looks good:

I had a lot of trouble measuring the depth though, so it's likely that this is either too deep (coils will try to ride over each other and bind up), or too shallow (cap won't seat properly). Hopefully too deep and I can maybe sand it to fit.

So now I need to separate this from the superglue arbor, make a slot in the rim to allow the wire to pass in (only so that I can use it as a mainspring winder), and make a hole near the rim to hook the spring on.

Hmm, my normal technique for getting it off the superglue arbor isn't going to work because I can't grip it.

I slid a knife underneath it, but I think it's not as flat as it was.