Threads in frame for grip screws

[CAP Black]

If the screw hole gets buggered up a little how is the best way to get those "chased back" to being good again. Any help will be appreciated.
Thanx
Jack

[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

[alanint]

Always remember.......a gunsmith's best friend is a home gunsmith!!!!

[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'...)

[sheepherder]

Originally Posted by alanint

Always remember.......a gunsmith's best friend is a home gunsmith!!!!

Took me a bit of thought to 'get' that...

So, an auto mechanics best friend is the backyard mechanic???

[alanint]

Yep, a trained gunsmith can almost be guarranteed 2-3 times the billable hours once a home "gunsmith" starts fiddling with a project beyond his capabilities!!

[CAP Black]

There is no doubt in my mind. I just like to stay on the right side of the knowledge line. I try to practice the concept of "know thyself." And I hate it when I'm wrong.

[lugerholsterrepair]

Jack..I'll ponder on it some more and await for the calvary to come forth with more help

Did you want to invoke the help of Jesus at Calvary where he died or were you wanting the CAVALRY ..horse mounted troops?

Just curious

[CAP Black]

By calvary I meant that host of old experienced pros, of this forum, who have fought their way through many, many obstacles like this one and even much more difficult. As you know, those masters of the craft have many pointers to pass on.
Jack

[lugerholsterrepair]

Jack, Jesus died at Calvary..How does that relate to any of these old pros who have fought etc?

[hgreer2]

The Whitworth thread was the world's first standard [1], devised and specified by Joseph Whitworth in 1841. Until then, every industry had used their own screw threads. The new standard specified a 55° thread angle and a thread depth of 0.640327p and a radius of 0.137329p, where p is the pitch. The thread pitch increases with diameter in steps specified on a chart. The Whitworth thread system was later to be adopted as a British Standard to become British Standard Whitworth.
In the USA, BSW was replaced when steel bolts replaced iron, but was still being used for some aluminium parts as late as the 1960s and 1970s when metric based standards replaced the Imperial ones.




Harry

[LugerVern]

I have always used both the tap and die.
Often after over torquing the screw threads will be damaged also, chasing both will ensure no further issues.

Good Luck

Vern

[John Sabato]

Yep, a trained gunsmith can almost be guarranteed 2-3 times the billable hours once a home "gunsmith" starts fiddling with a project beyond his capabilities!!

Posted on the wall of the late master gunsmith, and my friend, John Dusing, God Rest His Soul, who unfortunately was only able to teach me a small portion of what he had learned in a lifetime... and I am grateful for every scrap of knowledge he gave me...

Gunsmith Hourly rate: $25.00 (BTW, these are 1970 rates)

...If you watch, $35.00!

...If you attempt to help: $55.00!

(we never had many clients attempt to help )

[sheepherder]

Originally Posted by John Sabato

Gunsmith Hourly rate: $25.00 (BTW, these are 1970 rates)

Interesting you should post that, as that is what I charge for my labor in 2011...Of course, I'm a gun hack, not a gun smith...

But I only take work that interests me...Production work gets a thumbs down immediately...I don't usually charge for setup, unless it involves a lot of muscle or fabrication...

A good example of what interests me is a guy on another forum who has made a laminated Enfield buttstock to military configuration and needs to drill the hole for the butt stock bolt...I would use the original buttstock as a template and I would clamp it to my angle plate to locate the hole and then clamp the laminated stock to the plate and drill it with my lathe chuck...(I might make a simple wooden cradle to hold it securely)...

Something like that would take me an hour or a bit to set up and maybe two minutes to do...and I would charge $.00...because it interests me...

...Now...What was this thread about???

Oh, yeah - grip screw holes! If this was a shooter, I might peen the hole edges and re-tap/chase it then...In the mill...Maybe even peen it for a collectible...Depends on how bad the threads were buggered...

Or you could drill it out oversize, and press or thread an insert in (something like the M1911A1 uses)...and then tap that...That wouldn't need re-bluing...Just touchup...You could weld in a plug and tap it, but that would require re-bluing...

[ithacaartist]

Received the BSF 3/16"-32 bottoming tap in the mailbox today from e-taps. After work, I chased out the offending grip screw hole. All went well, did not need to feed it thru the frame from the good hole's side, nor fuss around setting it up for the drill press. Feeling for the right "start", it became evident that I could run it gently through by hand and have the tap remain perpendicular all the way.
BTW, I did try the thru the frame method, tempted by how much of the tap's shank was relieved to clearance diameter. Lucky again, there was just enough room between the walls of the mag well to allow the tap to be applied in the manner I suggested above!