On Sat, 1 Mar 2008 07:08:13 -0500, "Backlash"
wrote:


"DoN. Nichols" wrote in message
...
Thermal expansion is a killer when you are aiming for precision.
If you have flood coolant, you will have less problem with this.
Otherwise, the only choice is letting it cool for a *long* time between
rough cut and finish cut.

Good Luck,
DoN.

--


Since I have a one man shop at work, I have a compressed air hose at the
headstock end of my work lathe, and use a high volume/low pressure nozzle to
cool the part down before taking measurements. Cool part, go get a drink of
water, come back and measure. If I am more pressed for time, I will use a
can of high flash-off spray degreaser to chill the part down faster, waiting
after each shot, and checking for temp on the part with the back of my hand,
before measuring. A non-contact laser thermometer can also be used. Another
trick that the air is good for is to mount a flex hose blowing low pressure
regulated air through the headstock bore to keep chips from tumbling around
the end of a boring bar on a through bore, potentially deflecting it in use.
This automatically keeps the part cooler while machining.

RJ

Im reminded of the time I was turning a shaft collar on the lathe, and
using the shaft to check for fit. I slipped the shaft into the collar,
and had the phone ring. Finishing my conversation..I was rather
chagrined to find that the collar, a nice snug slip fit, had cooled
off and had shrunk onto the shaft, requireing a bit of a go at the
hydraulic press to get them apart.

Ive not made THAT particular mistake since.

Other mistakes however....sigh

Gunner