Thread Problems Part Failure

Agreed, radial. I have taught at a vo-tech for short time, and the first thing was to teach them the correct way to do a job safely. Some were more proficient than others, and once they grasped things some could handle other ways to go about a project. Others, well, lathing was the term some never lost :).
 
Think that you have problems (-:
I finished turning all of the OD and ID diameters of 64 parts today. Monday I will begin the internal threading, 24 parts 2"-4 TPI Acme, 12 are RH and 12 LH, followed by 40 parts 1 1/2"-4 TPI Acme 20 RH and 20 LH all in 1018 steel.

Before leaving at 3:00 today I turned a 2-4 TPI LH Acme male gauge plug in aluminum to get a handle on the thread depth required for these Vardex inserts, measured it over wires, (had to tweak it 3 times) then made a test nut in aluminum using the same thread depth and it screwed onto the GP Acme threaded rods by hand, a bit tight as I was right at the pitch diameter listed in the tables, adding .002 to .005 to the depth will make it just right.

This is the plug, Monday should prove to be a rather trying day, I have roughly 21 hours to finish all of the parts, wish me luck.
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20151016_171556_zpsdaklbljr.jpg

20151016_171556_zpsdaklbljr.jpg
 
Fun stuff! Had to do a 1 3/4-5 TPI full acme rod about 18" long a couple of times. Building a 'C' vise for pipe. Then had to do about a 5" long nut for it! The nut was welded to the frame afterwards. That stuff is fun to me!
 
Paul in OKC said:
Fun stuff! Had to do a 1 3/4-5 TPI full acme rod about 18" long a couple of times. Building a 'C' vise for pipe. Then had to do about a 5" long nut for it! The nut was welded to the frame afterwards. That stuff is fun to me!
Click to expand...

Very familiar with C-style pipe vises. One's I've dealt with over the years has a 2"-4 Acme thread on them. The latest one's I've had to deal with have a M55x4 Trapezoid thread! Glad I didn't have to cut them. Just had to disposition them as good or scrap.
 
Paul in OKC said:
Fun stuff! Had to do a 1 3/4-5 TPI full acme rod about 18" long a couple of times. Building a 'C' vise for pipe. Then had to do about a 5" long nut for it! The nut was welded to the frame afterwards. That stuff is fun to me!
Click to expand...
The LH threading did not work at all, these tools have the helix angle built into them, which is diameter specific as well, the LH tool should arrive tomorrow. using a RH tool to make a LH thread had the helix angle 180° apart, this cannot possibly work, well..
Also, each part took 125 threading passes or 4000 passes for 32 parts, good thing that I used a CNC lathe or I would be typing this from prison right about now.
 
Never had trouble using RH inserts for LH threads, but always been a 'V' thread, or stub acme. Not had to do a full acme LH, could see where that depth might give ya fits!
 
The inserts are laydown triangle and are symmetrical, the holder has 3+° of angle, when ran left handed that's 3° in the wrong direction, an insert with enough relief on both sides in a holder with zero angle would work both ways.
The helix angle for a 1 1/2-4 thread is 3.06°
 
Ok so what worked for me?
1. I used a live center. Made all the difference.
2. I tried both approaches live center and bumping (Not ramming lol) I will say both worked flawlessly without any issues. So I would say gimme six of one and half a dozen of the other. On bigger threads 1/2 up I will center drill more than likely, but as Paul said just bumping my center into the part to make a dimple and lock it down, worked just as good as center drilling.
3. Lighten up. What I mean is at the point I was within .015 I started with .003 cut. Then within .006 I just would take .002 to depth. Each pass followed with a spring pass. Worked great there.
4. Patience. I know I want to send the tool in .060 and the part winds up threaded in the first pass, but it just won't work. : )

Thanks to all who helped. I shall continue on my learning way.
 
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