Lock tumbler

[Scota@4570]

I should have added this for the OP. Sounds like the mainspring is out? IF you have the mainspring out, and you do not own a mainspring vice, you have a problem. The Kibler mainspring are very strong and they are also fiddley to get back in. You need a mainspring vice. IF you try to use pliers it will probably slip, break in two and the pieces will fly with force. A real gunsmith may have a mainspring vice. Good luck.

 

[Mikekj]

Pitch refers to the number of threads per inch.

Threads per inch and thread pitch is not the same thing.
Thread pitch is how far apart each thread is.
Threads per inch is self explanatory.

“TPI is a numerical representation of the number of threads in every inch of length along a screw. The thread pitch is a measurement of the distance between two thread peaks.”