Ahhhhhhhhh yes, I know exactly what your talking about there. I'll
tell you how I know.

Was at work one day, and its supposedly against company policy to do
home projects, but we all know how that goes. Decent folks get
projects done on the sly others do not. Anyway a fellow came to me and
asked if I could machine a shoulder and reduce the round brass stock
he had and cut some threads on the end of it. He wanted to make a
brass shotgun cleaning rod out of some 5/16" diam brass stock he
scrounged. I said sure. I chucked it up in the lathe (about 3 1/2 - 4
feet total length. He was going to get an exact length later and cut
it to size. I machined the shoulder, and the lathe was still turning
the stock at a "resonable" speed. Someone came in the shop and he
got nervous, turned around and bumped into the speed change lever.
Lathe ran up in speed, and this brass rod bent in a 90 deg angle and
proceeded to catch him in the elbow. It was awfull. It fractured his
elbow big time. Not wanting to get me in trouble for his project, he
faked a fall out the doorway, at the back of the hanger where the
quarry tile at the threshold was always chipping off and had been
reported numerous times to the safety office as a trip and stumble
hazzard. This action finally got civil engineers to fix the doorway
thresholds tile, but his elbow has never been the same since. I have
tried numerous times to slip the lathe into a higher rnge but all it
did was grind gears, he however managed to do it just by accident.


Taught me a lesson, don;t leave anything any longer exctending out of
the lathes headstock than necessary, and don't allow anyone around you
when your using the machines......**** happens.

My pet peave is when someone just walks in and gets nect to you to
watch you make chips, or those that proceed to use the chip pan as a
foot rest while they shoot the breeze......

On Sun, 13 Jul 2003 15:19:31 GMT, (Gary Coffman)
wrote:

x-On 10 Jul 2003 16:32:36 -0700, jim rozen wrote:
x-You need to be more specific about the 'critical speed'
x-problem.
x-
x-What it means is, unless the entire shaft that protrudes
x-is *securely* supported along its ENTIRE length, the
x-machine operator will be confronted with a piece of
x-one inch diamter bar stock that has bent at a 90
x-degree angle where it emerges from the far side
x-of the headstock, and is WHIPPING around in
x-a huge circle at about 1000 rpm.
x-
x-Ask me how I know. :-(
x-
x-Gary

--
Visit my website:
http://www.frugalmachinist.com
Contents: foundry and general metal working and lots of related projects.
Regards
Roy aka Chipmaker // Foxeye
Opinions are strictly those of my wife....I have had no input whatsoever.
Remove capital A from chipmAkr for correct email address