Moulder Spindle Runout Tolerances

Some advice on acceptable precision in a moulder spindle. April 18, 2015

I run a six head, heavy duty, 8000 rpm molder with outboard bearings. Can someone tell me how much spindle run-out is too much and what it is caused by? On average I get .004 to .005 thousands run out on a 9" shaft.

Forum Responses
(Solid Wood Machining Forum)
From contributor U:
If you have that kind of run-out you have a problem that needs to be addressed. Look at the very base of the spindle where the cutter head come in contact with the spindle, you should see some numbers like 2/3 or 3/4 scribed in the base of spindle. These are the run-out readings when the spindle was manufactured from the factory. These reading are in microns and there are 25 microns to .001". If you’re getting readings like you stated in thousands of an inch I would suspect your out-board bearing needs aligning and you spindles need replacing or rebuilding. At the very least you need to contact a professional who can handle these issues.

From contributor U:
One more note, when you take run-out readings they should be taken with a micrometer, with the spindle belt removed and with no outboard bearing on the spindle shaft. You may have already done this - just making sure nothing is giving you a false reading.

From the original questioner:
I should have been a little clearer in my first post. I'm getting those readings with no outboard bearing and a head locked onto the shaft. With nothing on the shaft the readings are nearly perfect. With a head on the shaft I've seen it as bad as .012 out but I don't dare run it with it that bad. I loosen the nut and turn the head a quarter turn and re-tighten until I get it down to .003" or .004". Our tech seems to dodge the question on how much is too much. When I run it at over .004 or .005" out using the outboard bearing it rumbles pretty bad at startup.

From contributor U:
At this point I think I would call the manufacturer tech support. More than .001" run-out becomes a problem with bearings on the outboard bearing itself. Aligning the outboard bearing you will need two dial indicators that are capable of reading microns. Its tedious work and can frustrating even for the most experienced tech.