The Difference Between Two Safeties
I've gotten some questions about the difference between the Precise Metalsmithing Two-Position Safety Kit and the same style kit from Chapman. Both come from Brownells. If you have been reading these pages, then you know that I am pretty cheap, so my first choice was a Chapman Kit, below.
The first thing I noticed was that the swing pivot hole was to be tapped (by me) 6x48 and that the pivot would move up and down (a little) when operated. The little threaded rod is intended to be threaded into the shroud through one tapped hole and along the way through the pivot. I did not like this and decided to try a Precise Metalsmithing Two-Position Safety Kit, shown below.
The first thing I saw, the photo is poor, is that the metal is blued, and second, the pivot is much larger.
Both are threaded 6x48, but the PM pivot, left, is shouldered and provides a large bearing surface. The shoulder is tightened against the inside of the shroud.
Above, PM on the left, note the larger hole. The small hole provided by Chapman is intended to be tapped 6x48. Now 6x48 is a gunsmith tap and it is very difficult, if not impossible to find Class Three taps. All I have found are Class Two, or loose fit taps. Now a little looseness is OK in a thread intended to be tightened as tightening will remove the wobble, but as a pivot it never loses the wobble. On the other hand, it is very easy to provide less than 0.001-inch clearance between a round pin and a reamed hole.
And a bonus, the PM has vertical grooves on the part of the lever intended to be swung, preventing your finger from slipping.