Gunsmithing Square threads, anyone? Winnie bolt mandrel......

[JimT]

I need to make a mandrel to machine M70 bolt lugs. Unfortunately, Winchester is/was still in the stone age, using square threads in the bolt. If anyone could point me toward a reference that shows proper angles for the tool to cut said threads, I would appreciate it.

They also insist on using 1/4-32 bolts for the action. GL trying to find bolts with that thread pitch.

I know, I know.....just use an M700........

Coned breach
Extractor cut
Different threads
Oh my........

 

[bohem]

Re: Square threads, anyone? Winnie bolt mandrel......

Are you sure it's a truly square thread? I think it's an Acme thread. Double check that it's not an Acme thread, because if it is, you can just buy an Acme thread cutting tool from MSC or McMaster

 

[JimT]

Re: Square threads, anyone? Winnie bolt mandrel......

I found the answer to my own question. Pages 294-296 of <span style="text-decoration: underline">Machine Shop Essentials</span>.

The threads look square to me.

[img:left]

[/img]

This is the callout.

I was thinking about modifying one of these:

Grooving tool

Thoughts?

BTW, for you aspiring gunsmiths/machinists, <span style="text-decoration: underline">Machine Shop Essentials</span> is probably one of the best references I have found so far. The author really breaks things down.

 

[Victor N TN]

Re: Square threads, anyone? Winnie bolt mandrel......

Looks like you found what you were looking for.

 

[Kampfeld]

Re: Square threads, anyone? Winnie bolt mandrel......

I made mine using a .0625 grooving insert in my top notch holder.
It is a little sloppy but it tightens up just fine.

 

[colchester]

Re: Square threads, anyone? Winnie bolt mandrel......

Machinerys Handbook is also another great resource for this type of info I used mine for info to grind some tools to cut acme threads and square threads.