"Bill Noble" wrote in message
...

"Gene" wrote in message
news
On Thu, 12 Feb 2009 05:10:34 GMT, "Harold and Susan Vordos"
wrote:



Good advice. Also, don't buy into the mythological tale that all
threading is done with the compound, which is always set at 29.5
degrees. (That was good advice circa 1900 when using stringy hot
rolled stock. Certainly, you aren't doing *that* are you??)

Feed straight in with the cross feed, with a tool perfectly on center,
and zero rake..... you'll be fine! (12L14 is your friend......)
--


odd, everything I've read except your post says to use the 29 degree angle
to cut the amount of cutter edge in contact with the cut in half. My
lathe is only a 12X48 inch Logan/powermatic - I don't know if it is rigid
enough to do some of the things a larger lathe does, but I can try it some
time

There's a lot of conflict with chip flow when plunge threading. I do not
recommend you do it, although material choices and spindle speeds make a
huge difference.

Point pressure on threading tools is extreme due to the narrow tool and
depth of cut. Adding chip flow conflicts to the mix is a recipe for tool
failure. Stick with the compound for better tool life. Plunge thread
for finish passes, which will clean up the back side of the thread. Tool
must be VERY sharp, and depth of cut must be shallow, .002" max., with less
desirable.

Modern machinery (CNC's) that are capable of extreme spindle speeds tend to
have much better results with plunge threading, although I'd avoid doing so
even then if I had the option. You'll get much better tool life by feeding
at 29 degrees.

Harold