View Full Version : So who here has fit a thumb safety?
I am in the middle of doing it for the first time outside the armorer's course. Then I went at it with an Arkansas stone and didn't really care if it went too far and became a scant safety. Now I am deeply paranoid since it is my money on the line. The whole reason why I am fitting it is because it is a scant safety after another armorer fit it a few years back.
Post up your tips and experiences.
Take off the grips and take the mainspring out so you can see really well. Go slow and check constantly.
Go slow and check often.
Also remove the grip safety when fitting the TS
You can scribe the new safety where it meets the sear (in the safe position) so you know when you are getting close.
The 10-8 armorers block has a spot to pit the TS to help when filing to fit.
Patience is the watchword with a thumb safety. A few file strokes, test fit. A few more strokes, test it again. And so on. As others have said, remove the grip safety so you can watch the fit. You know you're getting close when you can insert the safety shank when you thumb the hammer back past the cocked position, but now when it's at the normal cocked position.
When I think the fit is right, I perform three tests. First, I cock the hammer, apply the safety, and release it. If the hammer moves forward at all, there's still a bit too much material. Second, I engage the thumb safety (keeping the grip safety removed) and try to pull the trigger. Watch for any movement whatsoever. Movement is bad ju-ju. The old military spec allowed for a slight amount, but now with modified sear geometries, shorter hammer hooks (often cut at negative angles), etc, you want no movement.
If it passes the "no sear movement" test, I go on to the "click test." Cock the hammer. Apply the thumb safety. Give the trigger a good, hard pull, with the safety on. Now, de-activate the safety, but do not pull the trigger. Hold the hammer-end of the gun up to your ear, and slowly thumb the hammer back past cock. If you hear a little "tink" sound, that's the sear resetting because the TS has allowed some sear movement. Repeat this half a dozen times to be sure. I've seen a bunch of factory Kimbers and Colts that would fail this test, either consistently, or every two or three times it was performed.
DISCLAIMER: I'm not a professionally trained gunsmith. I'm learning slowly by reading and listening a whole lot to knowledgeable people.
I got it fit. It is a little rough but it is acceptable. The reason why I stopped filing once it worked well without letting the sear move was because the previous safety that let the sear move still had a line on it from wear. I could not remember from class if we file to the point it no longer leaves a line. I figured it would be better to have "too much" on the safety lever as long as it works rather than too little and it doesn't work.
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