"Paul Weber" wrote in message ...
I got at auction a Clausing 5900 12x24. In setting up a chuck I found
.0025 radial runout on the nose taper. The spec is less than .0005. Is
there any kind of bearing problem that will cause this? The runout is at
the same position every rev. The bearings appear to be as tight as they
will go. Thanks Paul


I tend to approach these scenarios a bit differently. Most folks seem
to take their readings as gospel right off the bat. One thing I've
learned is that getting a good read on an indicator is very difficult.
I would never tear something apart until I analyzed the data at hand
six ways from Sunday. I wrote a small article titled "The potential
Folly Of indicators" that addresses this issue. There is always time
to tear something apart, but be mindful of the old axiom "If it ain't
broke, don't fix it!"
Right off the bat, I'd want to know if you are truely reading runout,
or surface irregularities on the spindle. One example: The LOO spindle
employs a key on a long spindle taper (the "L" in LOO stand for long).
There is only one position where the chuck will mount. This leaves a
virtually untouched portion of the spindle where the backplate has a
keyway cutout. The rest of the spindle gets its share of battle scars
over the years. This can cause the spindle to appear out of round. In
this case, it is, but the backplate never contacts the portion that is
reading high.
A similar reading on the internal taper that coincides with the same
position on the outer taper may rule this out as the culprit.
Small surface irregularities certainly read differently on an
indicator than runout. To get an idea of how runout reads, you can
chuck something up in a 4 jaw chuck slightly off center and observe
the dial movement.

I guess my point is never start with the assumption that your data is
beyond reproach. Rule out human error as a possibility before assuming
a mechanical error.

Good Luck.
Dave Ficken
Meridian Machinery
http://www.mermac.com

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