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A Bad Fly or A Trash Lock?

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This 7 month-old small Siler lock is not engaging at half cock much. It will 'click in' half cock fine several times and then it will roughly skip over the half-cock but engage solidly at full cock. This happens both on and off the gun so I believe it's not a lock mortise issue. Also, I checked the bridle and its not too tight nor loose.
Interestingly, when the lock isn't engaging at half cock, if I give the side plate a good stiff tap, it will thereafter click nicely into half-cock a few more times. (That's why I think it's a bum fly). Same thing when it's off the gun; a good tap on the cock screw head and it will then engage in half-cock.
I have it very well lucubrated with clipper oil.
I compared it with another small Siler lock I have and in comparison it looks really crude and obviously unpolished. It's on my Sparrow pistol, so I was wondering if rather than sending it off to be repaired ($$$), maybe I can take the lock apart myself (a first time doing that for me) and just remove the fly. Or, is this lock just trash? (Pics attached)
I'm bummed that I have to do this with a new lock that came from a pretty reputable dealer.
Thanks,
Bob
If it’s 7 months old, call the place.
 
Hi Bob,
If you have time, why not use your lock as an opportunity to learn some lock gunsmithing. Take it apart and first run a flat bastard file across the inside face of the lock. It will show how flat it is. If it needs flattening, file it flat and then use oil and stones or sand paper backed by a flat block and dipped in water. Once flat and polished, use stones and oil to clean up all the casting surfaces on the internal parts and polish all the bearing surfaces. Go light and remove as little metal as you can but still get rid of any rough surfaces. I would leave the tumbler post and tumbler hole in the plate alone except you can dust them with aluminum oxide powder or rottenstone and a little paraffin oil (lamp oil) then rotate the tumbler back and forth in its hole. It will polish the surfaces without adding any appreciable slop to the fit. Then buy and install a new fly. Clean everything up, reassemble the lock sparingly grease every surface on which something slides and sparingly oil every surface in which something rotates. Then off you go. Sure you can return it but the new lock may not be much better and it may differ slightly needing inletting.

dave
 
tum.jpg

This is old, but if it is still not solved..... Firstly, please use legible pictures. If the picture had no detail, fix it. I used MS picture manager. It would have been easier if it was a JPG or similar, not a webpage.

Anyway, The fly is in the correct foreword position . The sear will miss the half cock. Good. In the rearward position it needs to follow the yellow line I inserted. IF those are true the fly is shaped right.

If it still does not work then it is not moving freely. Often the bridles on these cast locks are to tight on the tumbler. That needs to be addressed. Loosing the bridle screw is not an acceptable fix. Once the bridle is fitted properly the fly should move in it's mortice freely. IF not, fix that. The fly must must be smooth. The pressure of the sear spring acting on the sear squirts it forward just past full cock. It must be smooth for that to happen. There must be reasonable sear spring pressure. Given all that, it will work.
 
Them things is tricky, polish and lube. I have added a fly to a lock that was for a single trigger but I installed a set trigger. It is tough to make those little thingys and to cut the tumbler.
 
It looks like a kit. Those rough parts aren't typical of a lock from Chambers. This is a learning opportunity. Disassemble it and polish all the contacting surfaces. A new fly is already hardened and can be replaced.
I have built several Siler kits. They come as cast and take a lot of polishing, grinding, drilling and heat treating of parts to be done properly. To me that does look like the kit model not finished as it should be. The regular locks are finished so much better.
 
Hi Bob,
If you have time, why not use your lock as an opportunity to learn some lock gunsmithing. Take it apart and first run a flat bastard file across the inside face of the lock. It will show how flat it is. If it needs flattening, file it flat and then use oil and stones or sand paper backed by a flat block and dipped in water. Once flat and polished, use stones and oil to clean up all the casting surfaces on the internal parts and polish all the bearing surfaces. Go light and remove as little metal as you can but still get rid of any rough surfaces. I would leave the tumbler post and tumbler hole in the plate alone except you can dust them with aluminum oxide powder or rottenstone and a little paraffin oil (lamp oil) then rotate the tumbler back and forth in its hole. It will polish the surfaces without adding any appreciable slop to the fit. Then buy and install a new fly. Clean everything up, reassemble the lock sparingly grease every surface on which something slides and sparingly oil every surface in which something rotates. Then off you go. Sure you can return it but the new lock may not be much better and it may differ slightly needing inletting.

dave
My thoughts as well. I got past my initial hesitation of taking it apart (mostly), and can see how it looks sloppy in there and am sure I can get good advise on any steps to take. I will need some polishing stuff and of course some dedicated learning time which is going to be something I will need to plan for.
I feel somewhat more confident now though.
 
I have built several Siler kits. They come as cast and take a lot of polishing, grinding, drilling and heat treating of parts to be done properly. To me that does look like the kit model not finished as it should be. The regular locks are finished so much better.
I know there was a shortage of them when I ordered this kit from MBS, so perhaps he went with something less than usual quality?
 
View attachment 208214
This is old, but if it is still not solved..... Firstly, please use legible pictures. If the picture had no detail, fix it. I used MS picture manager. It would have been easier if it was a JPG or similar, not a webpage.

Anyway, The fly is in the correct foreword position . The sear will miss the half cock. Good. In the rearward position it needs to follow the yellow line I inserted. IF those are true the fly is shaped right.

If it still does not work then it is not moving freely. Often the bridles on these cast locks are to tight on the tumbler. That needs to be addressed. Loosing the bridle screw is not an acceptable fix. Once the bridle is fitted properly the fly should move in it's mortice freely. IF not, fix that. The fly must must be smooth. The pressure of the sear spring acting on the sear squirts it forward just past full cock. It must be smooth for that to happen. There must be reasonable sear spring pressure. Given all that, it will work.
I can see how the fly extends more than the one I removed from this lock. My guess is that someone ‘polished’ it more than they should have, though nothing else in the internals has been polished !
 
The finish on the tumbler is OK. I see machine marks. Somebody took the time to machine and finish after casting. Some of the cats part locks I have worked on look like they were tumbled with a bunch of rocks and left that way after casting. I have no ide on the rest of it. The pictures lack detail.
 
I had an issue with the “Large Siler Lock” that came with my John Armstrong Rifle Kit I bought. I finally discovered after a lot of tinkering that the “Fly” had not been properly hardened and the sear was actually digging into the fly and creating a small notch that would catch whenever the set trigger was used. I replaced the fly with one I got from Track of the Wolf and have had no further problems. Cotton
 
It wasn’t that big of an issue, just bought another fly then fitted and hardened it. I was fitting and polishing the components to the lock anyways.
 

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