Internal Acme Threads...

[cdhknives]

Yet another practice piece to see if I can build the skills before parting with $200 for my form 1...

I spent the last week on and off working on a muzzle brake cover to fit a YHM QD 30 cal brake (normally on my Rem 700 308Win). This was dual purpose, to practice and to reduce ringing ears during long sessions at the range. No I don't always shoot suppressed...

Anyway, I didn't think my old Atlas 10x36 (QC54 technically) had the mass to cut ACME threads with a true form tool so I ground a thin tool and planned to take multiple passes. This quickly became a real hassle.

Is this old Atlas of mine up to the task of using a true full size ground form tool to cut internal ACME threads or am I stuck with light cuts and a lot of them?

 

[gi_984]

Good question, I've got a 12X36. Haven't cut acme threads on mine but I don't see why you couldn't on your 10x36 as long as you have a rigid set up. Look up Lyle's (Mr Pete 222) youtube video on ACME threads. It is machining tips #24 &#25 if I remember correctly. I'd recommend buying a copy of his "How to run a Atlas lathe" video series that he sells. Has four chapters on cutting internal and external threads on the 12X36.

 

[pdentrem]

I have done square threads on my Atlas 10" for my Savage 99. Used a form tool for that. No issues, many smallish passes at the end. You can rough out the Acme threads with a regular V tool and follow up with the Acme tool to finish if needed.
Pierre

 

[randyc]

I have done square threads on my Atlas 10" for my Savage 99. Used a form tool for that. No issues, many smallish passes at the end. You can rough out the Acme threads with a regular V tool and follow up with the Acme tool to finish if needed.
Pierre

Hi Pierre, I wasn't aware that the 99 had acme or square threads. Would that be the barrel/receiver interface ? (Your method for producing the threads sounds like a good one !)

 

[pdentrem]

Randy
The 99 used 12 tpi Square right up to the shoulder on the barrel shank. See pictures. It is surprising the variety of thread types used in the firearms over the years. Mostly V type but lots of Square and some weird ones. Like the Ross rifle used a what looks like a buttress Acme thread and the Danish Krag 1889 looks to be a tapered pipe thread.
Pierre
View media item 94635View media item 94636

 

[rgray]

I to opted for cutting with a 60 degree threading tool first then following with the acme tool. The acme tool is much happier squaring up the V than cutting from scratch.

 

[gi_984]

Interesting, I've never heard of roughing out with the traditional 60 degree threading tool first. Makes sense though as long as you don't have a problem picking the thread up. How far did you cut with the 60 degree before switching over to the ACME tool? Did you just switch out the threading tool without moving the tool holder?

 

[rgray]

Interesting, I've never heard of roughing out with the traditional 60 degree threading tool first. Makes sense though as long as you don't have a problem picking the thread up. How far did you cut with the 60 degree before switching over to the ACME tool? Did you just switch out the threading tool without moving the tool holder?

I went full depth with the 60 degree. Course only the point is full depth. Leaving the sides for the acme tool to cut. I did it with the angled compound for the V thread. Once that is cut the acme tool is advanced straight in.
On the internal thread using a boring bar with a square hole for a tool bit the change out is simple as changing the bit. On the external I changed out the bit in a QCTP holder. If both are pressed against the rear wall of the tool holder the change out is simple there also.

 

[randyc]

Randy
The 99 used 12 tpi Square right up to the shoulder on the barrel shank. See pictures. It is surprising the variety of thread types used in the firearms over the years. Mostly V type but lots of Square and some weird ones. Like the Ross rifle used a what looks like a buttress Acme thread and the Danish Krag 1889 looks to be a tapered pipe thread.
Pierre

Thanks, Pierre ! Learn something new every day. The 99 was ahead of its time in almost every respect, in my opinion. I have one in .300 Savage and it's a sweetheart.

I have only two lever-actions; the other is a Marlin .45-70 boomer, also a lot of fun ! I collected only bolt actions for many years until I shot a 99 at the range about twenty years ago. It opened my eyes about the so-called inaccuracy of lever actions.

The Krag-Jorgenson rifle looked like it was DESIGNED by a pipe fitter, LOL

 

[barnett]

Randy

Whats wrong with being a Fitter ?! LOL