Threads in frame for grip screws

[ithacaartist]

Hey Jack,

I'm about to embark on the same journey; I, too, have discovered buggered grip screw threads on the left side of the frame of my better '06 AE. Someone ran the screw in fairly far, cross-threaded, and the screw does not tighten closely enough to secure the grip. The threads are Whitworth format, not SAE or Metric. I was just about to search the threads (on the forum, not the gun) and find the one I remember from a few weeks ago, in which this was discussed. In that post are mentioned the correct size and pitch. The taps and dies are available on line, I've found from Googling.

Here's a thought I had about the job:

Chasing threads out can be tricky if the tap starts to cut yet another set of threads instead of cleaning out the originally intended grooves. Worst case would be 90 degrees out of phase, and the new groove would run in such a way as to almost completely remove the lands of the old thread, resulting in further loss of steel to the extent that you'd be approaching a clearance hole in diameter. The screw would turn in just fine until you hit bottom, at which point the tightening power would serve to strip out whatever remains of any threads.

Lining the tap totally perpendicular to the surface is paramount, as is getting the cutting edges to start so that they cut/clean only the former thread groove, and not remove any more meat from the frame. Also, don't forget cutting fluid for lubrication.

Once I have the correct tap, I'll approach the messed up hole from the back side. This can be accomplished by gently turning the tap through the opposing hole from the outside, and through the mag passageway. This way, the tap can be started in the end of the messed up hole with the most material remaining in original threads/condition. If the array of cutting teeth on the tap turns out to be too long to engage only one hole at a time, grind down its shank enough to allow the tap to leave off its contact with the first set of threads before it encounters the set you want to clean out. This will allow you to "feel" for the remnants of the correct path, and not be bound to the orientation of the first threads--which may be out of phase with those on the other side of the grip, as I mentioned above.

If the threads in yours are not badly buggered, then what I've suggested about lineup may be unnecessary. Use magnification to see, and you'll be able to tell at the point the tap is first engaged, whether or not your work will remove material in the right way.

I hope this helps, and that I've detailed the features of this job enough to give you the reassurance to do it, and not frighten you off from it completely!

David Parker

p.s. I'm envious of your Luger collection; the stuff you've showed us so far is in exquisite condition!

[CAP Black]

Yeah, David, you seem to have hit the problem right on the nose. You obviously have thought through the dilemma in more depth than I had. Lots of things I like to do myself but I get upset with myself when I try to take on a job that should go to a gunsmith. Its just hard to know the WHEN of it all. Getting through on the back side may require making a gadget to get from HERE TO THERE. I thought about taking a good screw and plenty of oil and running it through from the back side. I don't know. I'll ponder on it some more and await for the calvary to come forth with more help.
Thanks. You have kept me from making a big mistake.
Jack

[sheepherder]

Originally Posted by ithacaartist

I was just about to search the threads (on the forum, not the gun) and find the one I remember from a few weeks ago, in which this was discussed. In that post are mentioned the correct size and pitch.

Probably this one -

http://forum.lugerforum.com/showthread.php?t=25753

The member who did the testing of the three taps found that 3/16" x 30tpi and 3/16" x 32tpi are indistinguishable on the thin Luger frame...

(That thread might make a good 'sticky'...)