Threading issue.

[bigngreen]

I wanted to update this thread with a big THANKS for the help!! I recently got a new PM 1340 GT lathe, all loaded up with DRO and three phase with VFD and such, I was super excited to give it a run threading. Got the results I was looking for, nice, smooth, sexy threads! I threaded a chunk of Remington factory barrel which has been what's been giving me fits, the brake threads on all the way super smooth and with only four turns on the threads the brake has only .001 play. Super happy and digging the DRO!

 

[Bob Pastor]

Hi Bigngreen,

The Arthur R. Warner threading kit comes with a neutral and a positive threading insert. Use the positive insert on CM. For fine threads only take .002 per pass and use your slowest speed. Call me if you are still having problems. Bob Pastor 1-269-521-3671. I'm on Eastern Standard Time.

 

[Leeroy]

I grind my own HSS tools. Very sharp with lots of clearance. I set my compound at 29.5 degrees and feed with it 2 thou per pass, then down to 1 thou per pass and then 1/2 thou per pass.

Dennis it must take you an age to cut a full depth thread at those depth of cuts..
I use full form carbide inserts, thread at as fast a speed as i can manage(usually around 200 RPM) and for the first three or four passes in feed at 0.010". I don't bother with setting the compound, i just plunge straight in.. I'll then back off the DOC to 0.005" until I'm close then down to 0.001-0.0005 for the finish passes..
My threads are a smooth as any I've seen.. The only time I've ever had problems with threads tearing etc is with hammer forged stainless barrels (read tikka barrels). I normally use neat cutting oil but a good dose of "Rocol" cutting fluid is needed to get these barrels to cut smoothly.

Cheers
Leeroy

 

[Jkob]

dennis it must take you an age to cut a full depth thread at those depth of cuts..
I use full form carbide inserts, thread at as fast a speed as i can manage(usually around 200 rpm) and for the first three or four passes in feed at 0.010". I don't bother with setting the compound, i just plunge straight in.. I'll then back off the doc to 0.005" until i'm close then down to 0.001-0.0005 for the finish passes..
My threads are a smooth as any i've seen.. The only time i've ever had problems with threads tearing etc is with hammer forged stainless barrels (read tikka barrels). I normally use neat cutting oil but a good dose of "rocol" cutting fluid is needed to get these barrels to cut smoothly.

Cheers
leeroy

ditto!!!!

 

[JerrySharrett]

Think of what you are doing guys. On a vee thread and on a small lathe the first few cuts can be deeper per cut (say 0.005-0.010 total) then after the thread gets deeper you now are having more surface area and are removing more metal per increment on the dial. So, as you get deeper back off some on each pass.

The last few passes you need to feed, say about 0.001", then make a spring pass (no feed). On the last 2-3 passes, just take passes with no infeed. This takes the cutting pressure to zero and smooths the thread surface.

As to how much to feed per pass it depends on your lathes rigidity, type cutting tool (HSS or Carbide), the tools top geometry (is it positive rake or neutral), the tool shank overhang and rigidity, rpm, etc.