S&W lockwork geometry and case hardening questions.

[mountaindrew]

I am embarking on my first large scale gunsmithing project, So expect to here more from me in the near future.
Well I just bought a S&W 1917 that has been abused in the past bu some hamfisted gunsmithing, and it is my quest to repair it, as well as do a few custom mods to bring it back into service.

The first problem is a distinct notch/ catch in the double action trigger pull. I have diagnosed it ad tracked the problem down to the interface between the hammer and the trigger, specifically the transition between where the sear surface stops driving the hammer, and the little ledge below that takes over. The picture shows the area I am talking about.



Sorry wrong pic. Here:


The two surface catch rather than meshing smoothly. I believe this is due to over polishing of the rounded surface above the sear that drives the hammer back. This slightly changed the geometry, causing an interference. I slightly hit both surface with some 600 wet/dry and the catching lessened somewhat, but I am going to have to remove a little material from one surface or the other.

Which should it be? I am leaning toward the trigger, because it has already been modified, so if I cant fix it, I'll just replace it and start over.

Any advice?

My other question is about the hardening of these parts. I read thet they are case hardened and that working on them will remove the hard outer layer. Is this true? If so, the previous person might have already ruined the hardening on the trigger.
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If I can repair the geometry, should I get some Kasenit and try to re-harden the trigger, and maybe the hammer also?

Any suggestions on this one?
Thanks alot for any help, Drew

 

[Old Fuff]

Given the difficulty and expense associated with finding replacement lockwork for a Smith & Wesson model 1917, I’d suggest that you don’t polish anything unless you know what you’re doing.

Looking at your picture, I suspect that the D.A. sear mounted in the hammer face is too short, and is picking up the hammer too late. If this is the case you might be fortunate in finding a longer sear, which should cost far less then a new hammer.

Try www.e-gunparts.com

 

[mountaindrew]

Good call Old Fuff. I will order a new sear on monday and try it before I do anything else. It is possible that someone removed some material here and hurt the geometry. The interference that causes the catch looks like only a couple of thousandths.

What about the case hardening though? How can I tell if the parts are damaged?

 

[Old Fuff]

I would presume that at this point the case hardening has been damaged. It would appear that too many cooks have been working in the kitchen...

However after things are working you can reharden the lower part of the hammer, or upper rear of the trigger - but you won't get the famous S&W colors.

I'll explain in a longer post over the weekend. Right now it's past the poor ol' Fuff's bedtime.

 

[grendelbane]

However after things are working you can reharden the lower part of the hammer, or upper rear of the trigger - but you won't get the famous S&W colors.

Yes, I have done this before, and it is a lot easier than it sounds. Most people are going to tell you that you are crazy, however.

Last time I checked, that old N-frame was still running. I shot it quite a bit for several years with no problem, then traded it off to a friend. Still going strong after a quarter of a century.

 

[mountaindrew]

Old Fuff, you are a genius! I got a new sear from Numrich on friday. The new sear was significantly longer (.012" or so) than the old one. In fact it was slightly too long and wouldn't reset, but I was able to slowly remove stock (maybe .002" - .003") with 600 grit wet sandpaper on a flat surface until it was perfect, making sure to keep the original profile. then a couple of passes with some 1000 wet and installed in the gun. The trigger is wonderfully smooth now. As nice a double action pull as any I have owned.

I will still need to eventually re harden the critical surfaces.

How soft is this steel? I can use it for a while before I harden it can't I without ruining the parts?