Lathe Threading: Several Techniques

[Uglydog]

I've noticed several different techniques available for threading on a lathe.
I went back to the old texts and attempted to plow through which is preferred and why, and was quickly overwhelmed with the details and complexity of the old masters.
I've found that if I'm able to get my head wrapped around the big picture then I can better understand the complexity.
Turns out there are several methods.

Once again I was fortunate to stumble on Rick Sparbers work. His clear explanations are astounding.
http://rick.sparber.org/spt.pdf (document attached)

Turns out I somehow fell into using the Parting Tool Method for my larger lathes, and the Traditional Method for my lil'hobby lathe. I'm looking forward to trying out the Malcolm Method.

For those of us wrestling with our first threads, Mr Sparbers work may be immensely valuable. Thus, I'm posting it here. It wasn't very long ago that I cut my first!!

Daryl
MN

 

[Ed ke6bnl]

You may also want to see the Videos by Joe Pieczynski on threading very helpful, here is one

 

[Wreck™Wreck]

I only know one way to single point thread on a lathe.

Mount part.
Produce any features on the part needed for the thread, such as reduced diameters and undercuts.
Thread away either right to left or left to right, what could be more simple then that?
If you do not have gauges for external threads measure over wires, if you do not have internal thread gauges then make one over wires before turning the internal threads.
Done

What is the Malcolm Method?

 

[rgray]

I like the zero to zero method.

 

[Uglydog]

I only know one way to single point thread on a lathe.

Mount part.
Produce any features on the part needed for the thread, such as reduced diameters and undercuts.
Thread away either right to left or left to right, what could be more simple then that?
If you do not have gauges for external threads measure over wires, if you do not have internal thread gauges then make one over wires before turning the internal threads.
Done

What is the Malcolm Method?

The link to Sparbers document is attached.
This document is significant for highlighting the features benefits of the various methods.

Daryl
MN

 

[Wreck™Wreck]

Entirely to much work, I only in feed from the cross slide when manual threading at greater then 6 TPI, this has never failed.

Many CNC lathes with canned threading cycles have an approach angle field that usually defaults to 29 1/2°, I just leave it be. Some controls have alternating thread side functions which advance from the Z+ side one pass then the Z- for the next pass, never having used this feature I can't say if it achieves better (faster) results or not.

One may do this on a manual machine by moving the compound (set at 90° forward and backwards) between passes, it would be slow going I suspect.