Before the micrometer

[M. De Land]

I've been machining and making precision gun parts for about 40 years now and when I need things like sear edges or hammer notches filed or stoned perfectly I always build a jig of some sort for final fitting. It is especially important on small surfaces to keep them flat and square.
One can file say a steel block and inch square quite easily by proper file stroke as you can see the cut profile but on small parts it is almost impossible without a guide jig of some sort.

 

[coloradoclyde]

Just look at jewelry and clockworks....Lots of precision hand filing there....

Then there's medical instruments and prototyping.

Then there's printing but that's more engraving....

When filing doesn't get the tolerances tight enough, then the stones come out.

 

[M. De Land]

Sear and hammer notch engagements require level and square edges to avoid unsafe let off conditions and consistent breaking weight.Clocks and jewelry don't have the same leverage and width of surface contact requirements.
Apples and oranges situation in my opinion.

 

[coloradoclyde]

M.D...I agree, I wasn't arguing or comparing with you........ :thumbsup: