Does anyone know the CORRECT spec for this thread?

It is NOT the .528-13 60/5 Brownells uses for their taps. (At least as far as I can tell)

It is a Buttress or Sägegewinde thread, but I cannot determine the exact size and pitch. Any help or direction would be MOST appreciated.

I have that info SOMEWHERE.....I'll look. it has been on my mind lately too. I had been contemplating making some safeties.

Ask and you will receive.

From a Old Obendorf print I have had reconstructed from an old friend in Germany.

Modified Buttress.

Major OD 13,5 mm
Minor ID 11,9 mm

Pitch 2mm per thread

Flat on top of crest ,35mm
Flat in valley of thread, ,35mm
Depth of vee section ,75 mm

Angle of buttress 30 degree slope, with 90 degree rear face.

I have a full page drawing of the military sleeve, the only thing missing is the indexing of the threads vs the sleeve. That must have been on page two that I never received. As it is in old German, you need to realy brush up on it to read some of the notes.

I gave Brownells a copy of this print about 15 years ago because thier tap is wrong, but either they never bothered or they had a BUNCH of taps made up.

When I was cutting that thread all the time, I did not bother with the flat in the valley, but you will need to do the flat on the crest to fit some of the older pre WW2 bolts.

James Wisner
Custom Metalsmith

James,

Awesome! Thank you VERY much!

Is there anyway I could finagle a copy of that print from you? I happen to have a few captive Germans that are knowledgeable in technical German that can translate for me.

Re: Indexing, If you cut the threads first, on bar stock, could you not then appropriately mill and turn the remainder of the safety based on the termination of the thread form?

If I can get made what I am trying to make I will send you a couple for your amusement.

Mr. Wisner , thank you very much. I am confident now that this is the incorrect way to go about it, but it was worth a try.

Picture to follow