Help with thread finish on lathe, nothing I have ever seen before

Jbolt, I did go over that thing about the T nut and the tool post sitting firm on the compound. I have had that happen many times with an Aloris or other type of tool post install, exactly like you said.

I also had him thread with the compound at 90 and only using the cross slide to feed in. Nothing different (although I thought it would be worse since cutting with both sides)

Threading has a much higher feed rate than turning. Couple that with a slower surface speed and your comparing apples to oranges. Very good point and true, just tried to point out that it works fine for anything other than threading.

I asked about the tool holder if any damage or anything, said he has been using the same one for years without any problem, but that I do not know. If he joins here he can answer these questions.

I did send him a link to AR Warner for one of their HSS tools and some of their cutting oil as I am not sure which cutting oil he is using.

He seems to be concentrating on the spring pass still taking a cut but only sometimes. Like MKJS said, it happens, it happens to me all the time so I am not sure?
 
It sounds like you have eliminated the mechanical issues. The only other thing I can think of is if the cross slide gibb is loose but I assume that has been covered. Spindle bearing issues will show in turning as well as threading so since that is not a problem everything seems to point to the tool or insert.

This is not meant to get into the discussion of using a compound or not but this machine is perfectly capable of cutting quality threads without using the compound.

The part on the right is a replacement for a Bostar CXA tool post (left). Material is A36. Threads were turned with a right hand "on -edge" carbide insert with the tool inverted and threading away from the shoulder. The compound was set to zero and locked using only the cross slide. The cutting forces are lifting the tool so this should be less rigid than a conventional setup yet the machine is perfectly capable of cutting quality threads in this fashion.

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Could the jaws be worn in the chuck? I have a 4 jaw with worn jaws, I use copper shims to overcome the wear.
Have a good day
Ray
 
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