Broken Top Screw

[t.caster]

So, I built a 1697 French fowler for a guy in our club about 2002. The top screw has sheared off for the third time now! It is a French lock from the M/G shop, bought from ToTW. I am tired of just replacing the screw if it is soft metal or so hard it is brittle. There is a slight gap between the top jaw and the cock riser that maybe allowing for shift, but it wasn't that way new. This was a replacement top jaw and screw, it failed when pulling it back for the fifth shot! I don't think the main spring is all that powerful.

Any ideas to solve this?

Thanks, Tom c

[rich pierce]

Test it for hardness and anneal it if it’s hard. Soft shouldn’t break.

[whetrock]

Rather than buying a new screw from TOTW this time, you might consider just making a new one from scratch from something soft like 12L14, or even just a piece of hot rolled steel from the hardware store/Lowes, etc.

[Daryl]

When I didn't have a lathe, I chucked up the material in a 3/8" adjustable speed electric drill and clamped that in the
bench vice.  Just using files, I made a LOT of things with that rig, including a small rifle primer firing device for my TC
cap lock rifle as  percussion caps were not available in Smithers back in the 70's and they could not be mailed either.

[Mattox Forge]

If you send me a drawing or a picture and some measurements, I will make you one.

Mike

[t.caster]

The thread is 12-24.

[Mattox Forge]

I made it out of O1 tool steel. It is not heat treated, I usually don't bother. They get dinged up like the originals did if they aren't heat treated, but it is easy to do with O1. I did not cut the driver slot, I figured you would want to do that..

I can send it if you PM me an address.




Mike

[smart dog]

Hi Tom,
Is it possible the top jaw is hitting the frizzen (battery)?  Looking at the geometry, it seems the top jaw may come really close to hitting the frizzen, particularly if the flint is a little short or worn.

dave

[t.caster]

Mike, pm sent

Dave, the only way the top jaw hits the frizzen is if the flint fell out before the attempted shot. Yes, if the flint got worn down too short, but that didn't happen this time.
Tom

[t.caster]

Update: I ordered 2 new screws from TOTW prior to my 1st post and they have arrived. They appear to be heat treated with a dark straw color, and a file won't scratch it. So I will aneal them and see how that goes. I also ground back the front edge of the top jaw so it's not hitting the frizz face.
The cam on the frizz appears to have warn down and doesn't flip all the way open most the time, but it does spark like crazy every time.