Sharp V threads

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heavyg603
Posts: 59
Joined: Thu Feb 16, 2017 1:17 pm
Location: NH

Re: Sharp V threads

Postby heavyg603 » Fri Jun 02, 2017 10:24 am

Harold_V wrote:
stephenc wrote:The very first thing I noticed was I had much much much better chip control .
The next thing I learned that really surprised me was instead of the usual 5-6 spring cuts I normally took I only needed two .
And visually the threads look better at the bottom with a flat instead of the sharp groove .
I've been converted ... no more sharp tip threading tools for me

Yep!
In regards to the use of a sharp point, if you'd examine the tip, you'd likely discover it well rounded (tip failure). That's a recipe for high tool pressure and skipping (intermittent) cuts. Yet another reason to not create sharp threads when not necessary (pipe threads are an exception). By providing the flat, you gain a serious advantage.

When I'm creating an A thread, I generally start with the major diameter on size (nominal). Once the thread is complete, I like to go over it with some abrasive cloth. The (reasonably) sharp crest is quick to deburr, and is readily reduced in size, which is a requirement for class two threads. Unless one goes crazy, even a class three will still be well within tolerance.

Harold


So a potentially dumb question on the flat. It is safe / acceptable to file a carbide insert tip to a flat ? I believe my tool has a small radius but not a flat. Most of my threads are in the 28 to 12 range if that helps.

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GlennW
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Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Sharp V threads

Postby GlennW » Fri Jun 02, 2017 12:01 pm

A radius is good, and only a max radius is specified for standard UN threads. A flat is optional.

A file isn't going to touch carbide as it is far harder than the file. I use a fine diamond lap to hone the proper radius when needed.

The problem is gauging the flat or radius. If you don't have a Comparator, it's pretty easy to mess it up and get it too large.

If you are just cutting standard UN threads the insert you are using is probably just fine the way it is with the .003+" radius.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

John Hasler
Posts: 322
Joined: Tue Dec 06, 2016 4:05 pm
Location: Elmwood, Wisconsin

Re: Sharp V threads

Postby John Hasler » Fri Jun 02, 2017 2:15 pm

heavyg603 wrote:So a potentially dumb question on the flat. It is safe / acceptable to file a carbide insert tip to a flat ? I believe my tool has a small radius but not a flat. Most of my threads are in the 28 to 12 range if that helps.


If the insert was made for threading leave it alone. You aren't likely to improve it.


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