Originally Posted by
lakeside
Well Geof I kind of agree with you and somewhat disagree.
A tight tolarance like is can be an issue on older machine when you have a true postional call out in an Orthogonal X Y Z datum plane. But as for holding a size ( even on concentricity) this should not be an issue as long as machine was not whaled on. If you can't hold the # you mostly need a service call.The machine may be out of calibration.
A machine that needs to hold True Positioning (Least Material Condition) is going to have a hard time in any shop. Even with a new machine. On the other hand Maximum Meterial Condition is a bit more forgiving. I'll have to agree with what Mike points out. Sorry Geof. .0005 isn't good enough for a used machine unless your making AGMA 11 Gear Blanks. The spindle on a Lathe usually runs-out about .00004-.00006 from the factory.
I was always told by a friend that has been a Tech for 32 years that you should look for a Repeatability within .00004-.00006 in all three axies. One may want to breakout the one millionths indicator for this one.
Also do not forget to check the Spindle Taper. Some of these older machines have had inexperienced individuals loading and unloading tools. I've seen guys drop CAT50 Tool Holders on the floor and just slap them in the machine without checking for dents, chips, or cement grit from the fall.
Toby D.
"Imagination and Memory are but one thing, but for divers considerations have divers names"
Schwarzwald
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
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