18 April, 2012

Fabricating a reproduction Sten loop stock (part two)

To read part one, click here. This is part two of a two part post.

Ok, now that I have resupplied with gas I applied heat and adjusted the bends so that I am happier with the arrangement.

I also found a piece of spare U-channel and bent it while orange hot. You will recall that the real Sten loop stock is made from this. You can see from the photo below that is deforms very badly and racks.

This happened in spite of some very careful bending and is the reason why I decided to use 10mm round cross-section rod and not U-channel. It could be bent with the correct tooling.

The next thing I did was CNC cut the attachment plate in 6mm plywood and cut two ferrules at the desired angle from 12mm round tube. This acted as a form which I then used to build a mould in Petrobond casting sand.

I then melted some aluminium in my 'flowerpot' aluminium foundry.

The hot air gun is my bellows and the furnace is fuelled with BBQ charcoal. The crucible is a pressed steel painters kettle. The flowerpot is lined with chimney cement and vermiculite. What you can's see here is the steel lid. This is extraordinarily hot and dangerous (DO NOT TRY THIS AT HOME). I am dressed head to foot in a full face visor, long welders apron and gauntlets.

Ok, now that the aluminium is ready I poured it into the mould.

Note the separate entry and exit holes (in-gate and out-gate).

I find this part really exciting. I never tire of removing a casting from the sand.

It looks a bit rough, but will clean up well.

After a quick clean up on the belt sander and the loop stock temporarily located in the ferrules, it is beginning to look the part.

Next I need to make it able to be mounted on the AGM Sten. So I drilled the hole for the existing blot and added another which fits into the channel at the back of the receiver.

After a bit more filing and sanding here is the finished result hanging up to dry outside my man-cave. It will dry much more matt.

And fitted to the AGM Sten (for some reason Blogger chose to rotate the image, tilt your heid please)...

It's lighter and more ergonomic than the nasty T-stock and should be robust enough. Of course only time will tell just how robust. I had originally planned to braze the ferrules onto the mounting plate, but on reflection casting as a single piece should be stronger than the brazing.

I am very happy indeed with the finished result. Of course it's not a exact copy of an original loop stock, but I set out to make something that would be a 'stand-off scale' replica and not an exact clone. I think I have achieved that.

Thanks for reading.