System Aydt Sear

[ddillson]

I have a System Aydt schuetzen rifle from which the sear is missing. Can anyone help me find the part or a good drawing so I can make one?
I know approximately the shape, but dimensions and details would save a lot of machining.

[JSnover]

I have a System Aydt schuetzen rifle from which the sear is missing. Can anyone help me find the part or a good drawing so I can make one?
I know approximately the shape, but dimensions and details would save a lot of machining.

I have one of those rifles, I'll dig it out tonight.

[ddillson]

Thanks! That would be great! A photo of the part on graph paper, with a part thickness would be very helpful. The dimensions of the spring would save a lot also. I plan on making a spring as designed, with the integral dovetail. I look forward to hearing from you.
Jim

[JSnover]

Here ya go. The piece is .298" thick. Hope this helps.
I'll take some measurements tomorrow, when it's a little easier to keep my eyes open but it seems like these rifles were unique to whichever shop they were built in.

[ddillson]

Wow, thanks! Is the paper 1/4" grid?
Jim

[Ballistics in Scotland]

This has been a very cheering response - reminiscent of an American correspondent sending me drawings and measurements which led to my making the trigger-guard and hammer for my Belgian Spirlet. Those were close enough to get good results with the first attempt in metal, after a wooden hammer with a projecting pin, around which I made a car body filler cast of the firing-pin tunnel. Fortunately the Aydt has no double action.

But with the Aydt (although I expect most of those small German makers bought actions from just a few or one factory), there could be quite a bit of variation in dimensions. Even if someone like Numrich have a condemned rifle, the sear might be a disappointment.

I think I would start by carving one (or several) from a hard plastic like plexiglass. 5/16in. O1 tool steel, which hardens in oil with minimum distortion and is freely available in engineers' suppliers and on eBay, is easily workable. You might even find that the slot in the other parts accommodates the full .3125in. thickness, letting you out of a bit of file work. A belt sander, even a hand-held woodworking one, can be useful.

[ddillson]

Hi Ballistics,
Thanks very much for the helpful suggestions. Your project looks much more exacting. The plastic model is a good idea. I think I have a piece of 1/4" Lexan around. The sear slot is .305, but I have a hobby mill.
I wonder if tool steel is appropriate. German gun parts all seem to be hardened, but I worry about the set trigger's let-off hammer becoming deformed if it is less hard than the sear. That part would be harder to replace. What do you think about carburizing the sear cocking notch instead of hardening the whole sear?
Jim

[JSnover]

Wow, thanks! Is the paper 1/4" grid?
Jim

Yep, 1/4".

[Ballistics in Scotland]

Hi Ballistics,
Thanks very much for the helpful suggestions. Your project looks much more exacting. The plastic model is a good idea. I think I have a piece of 1/4" Lexan around. The sear slot is .305, but I have a hobby mill.
I wonder if tool steel is appropriate. German gun parts all seem to be hardened, but I worry about the set trigger's let-off hammer becoming deformed if it is less hard than the sear. That part would be harder to replace. What do you think about carburizing the sear cocking notch instead of hardening the whole sear?
Jim

You wouldn't expect to have to hit the sear with a hammer to release the hammer, and the blow received from the little hammer in the set trigger is a lot lighter. I wouldn't expect there to be any risk of damage. But I am sure carburised mild steel would be fine. Proprietary case-hardening powders will probably do a better job than the old-fashioned bone dust, horn shavings etc.

What I would do, though, is differentially anneal it. First heat it red-hot and quench it. Then polish it bright - in which you must be careful, as it will be glass-hard and glass-brittle. Just hold the place you want to stay hard with a pair of pliers to absorb heat, and heat the rest gently until it is about purple. You can do this with one of the little torches that are filled from lighter fuel butane cartridges, or you can dip it in molten lead. Then lay it on a piece of ceramic tile, and watch the colours creep into the part the pliers have protected. Tip it into the water as soon as that part is a deep brown colour.

[ddillson]

Thanks! I'll give it a try. I was successful some time ago making a leaf spring for a Remington #4 (beautiful gun, 1929, still has case color on the receiver), because the original had broken early in its life. In fact, I might try making the sear spring out of the broken Remington spring. It has enough material to shape it and form the dovetail, once I anneal it.

[Ballistics in Scotland]

A spring is actually easier. You can just cover the glass-hard spring with mineral oil (car engine oil is fine) in a shallow vessel outdoors, ignite it with a torch, and when it has all burned away you should have a filthy but tempered spring. It might be a good idea to put in a similar sized piece of steel with no find shaping in it, to check for brittleness or softness, and if that goes wrong, harden the spring again. But it has always worked for me.

[ddillson]

Great! Thanks!