"John" wrote in message
...


It was me not paying attention to the dates of the last post. The
bandsaw
axle sort of got my attention. I bought a DoAll model C-80 out of the
scrap yard for 400 bucks a while ago and had to make new spindles for
it.
The bearings had spun on the axles and they had to be replaced as well
as
the bearings. The metal I used was from some of the scrap of the pins
I
made of the 4140. I still have a barrel full of the out of tol. pins
accumulated over the years. I just used another piece today to make up a
lathe chuck wrench. By the way to get a good finish on the metal you
have
to take at least ten thou. per side and turn at least 300 ft/min.


John

Is that the 4140 without sulfur? It's been so long since I've turned that
alloy that I can hardly remember it.



I switched suppliers after that bad batch and had no more problems with
cutting the metal. We had to supply certifications so I kept an eye on
the sulfur content and made sure it was always on the high end of the
limits. It ran on the high end of the permitted amounts, I only machined
it and didn't weld on it. I think the percentage ran about .18 At that
percentage it would run well at those speeds. The part we ran required
holding +/- .0005 in. on 6 inch turn and once the machine stabilized it
ran all day with almost no scrap. The only problem was the air chuck
would sometimes not hold the piece properly and it would slip if we had
the feed or rpm running too high. I made thousands of those parts.

Machining a lot of metal in batch- or continuous production really gives one
a feel for subtleties that we don't usually pick up in ordinary hobby
machining. If you made thousands, you must really know the material.

Note what Don reported about the standard for sulfur content in 4140 --
0.040% maximum. Another thing that shows up is slight "modifications" to
standard alloy specifications, sometimes done for a good reason. You may
have run into one of those circumstances. I've heard of 4000-series alloys
that contained more chromium and less carbon than the specs require, for the
purpose of meeting the elongation specification, which apparently is not
easy.

But, like most technical things about materials, I haven't spoken to
metallurgical engineers for decades. It used to be a major part of my job.

--
Ed Huntress