On 13 Apr 2005 12:26:48 -0700, wrote:

LLoyd, I found the problem. It turned out to be the key on the gear the
headstock gear that drives the threading drive was improperly seated,
and blocked that shaft tension adjustment nut in its travel. I used my
rawhide mallet to drive the key into its slot, and then the adjustment
nut was not blocked and could do its thing. The problem vanished. No
play in the headstock now (that is, less than 0.0001 inch).

My current challenge is that the majority of cuts I take are not
entirely smoothe, but feel threaded. I believe that this is due to the
carbide cutting tools that I'm now using, and I also believe the
solution might be to grind a few HSS cutting tools with rounded ends. I
remember going thorough this excise more than 30 years ago, but that's
been so many years ago that I don't remember the solution required to
get a very slick and mirror-like cut which I would like to do, but if I
recall corectly it involved the use of a rounded end cutting tool. (I
also recall that when we had a tools that would do this, we stashed
them away and literally guarded it with out lives.)

Any suggestions that exclude use of a tool-post grinder?


Harry C.

If the shaft feels "threaded", there are some possibilities.

#1, feed rate is much too fast, or spindle is turning much too slow
and you are actually threading.

#2 Gibs are loose on slide, apron, compound etc.

#3 Work piece sticking out too far

#4. Tool nose way way too sharp and is cutting into the work rather
than shearing along the work.

When I first started making chips, I used to get this all the time,
with an old Logan 10" lathe. And for all the above reasons.

This might help:

http://easyweb.easynet.co.uk/~chrish/t-finish.htm
http://www.finelinehair.com/home/tool_bits.htm
http://www-me.mit.edu/lectures/machi...the/intro.html


I tend to run between 800-1000 rpm on vitually anything under 2",
using HSS tooling
Steel, aluminum etc. Then adjust my feed rates to match. A good
start with a basic cutting tool is .005-,007 per revolution, YMMV of
course.

If its a steel I know well, or aluminum, I may crank it up to
2000-3000 rpm depending on many things, using carbide. With a decent
carbide bit, I tend to run my steel chips so they come off the work
piece colored brown or straw colored, or even up to blue. When
roughing, I mostly run blue chips. Shrug..while I like
machining..standing there all day making tiny cuts is like watching
grass grow. Most of my lathes are filled with high sulfer cutting
oil, so I often run the blue chip speeds and feeds with oil flooding
the cutting zone.

With some steels and a negative rake tool in a rigid lathe, Ive been
known to burn off .02 per rev and in aluminum with a big radius on
the cutting tool and still getting a good finish. But such is usually
only for hogging off material fast.

This may not be possible with your lathe. Some are stiffer, more
powerful than others. Shrug.

One thing a lot of people dont know about, which I strongly recommend,
is to take a socket head cap screw of the proper size and replace one
of the center gib screws on both cross slide and compound slide.

When taking a heavy cut, simply tighen them down a bit, particularly
the compound.

Oh..I tend to sharpen most of my HSS bits on a belt sander.
Shrug..gives me a good "grind" and is easy to tilt the table down to
your 10-12 degrees and get proper relief, and simply turning it gently
and quickly will give you a good radius on the tool nose.

I am NOT a machinist, nor do I play one on TV. But Ive picked up a
few tricks learned in CNC production shops that often translate to
home shop usage on lighter machines.

Gunner

Rule #35
"That which does not kill you,
has made a huge tactical error"