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Spindle runout issues


Jun 28, 2012
Mt Clemens, Michigan 48035
A solid one-hand push-pull in the parked spindle/tool holder should show the spindle is solid and not easily moved.

To partially rule out the tool holder you might try another tool holder to see if the runout is in the same clock position as to the spindle.

Consider that the length of the tool holder will magnify any wobble caused by an ill condition of the spindle taper.

Running an indicator on the OD of a tool holder may suggest a condition of wobble caused run out by error of the spindle taper.

If there is a wobble then a very short tool holder will reduce the amount of wobble.

*You might test the tool holder by setting the tool holder's straight diameter in a V block and indicating the taper at a few places along the taper lengths. if the tool holder in a V block runs true..and then runs wobble or run-out in the spindle this may suggest the spindle is in error.

Agree this does not test the collet holding portion of the tool holder.

It is very unlikely that a new Maritool tool holder would have a .003 OD error so the tram of the tool holder on one side and then the other would show the error indicating the tool holder od near the far-out end.

*A stub(very short) tool holder would reduce the effect of wobble run out...so to run some parts until you call in a spindle grinder hand, if tests show that is what you need.

Oh. a new Maritool tool holder that was in a hard wreck might be bent.


Jan 6, 2007
I have seen a thread lap, it was a copper expanding “ bolt” for all intents, load with abrasive run in and out etc, I have a sneaking feeling it was somthing from more jig grinding but not certain


Sep 23, 2013
I assume you have probably solved this since its been a while, but here's my .02 for anyone searching in the future.

First and foremost the taper looks terrible, while the right move is to put a qualified test bar in there-I absolutely would not, it will likely damage the precision test bar.

You need to determine whether you have tool rock and/or play in the bearing or mounting system. The truth is, the spindle is coming out either way because at a minimum this spindle needs a taper grind. It may have other dimensional issues, but you would need to measure it all up without the bearings on the journals. Once the shaft/taper is back in spec- air gauge in its AT class, and 300mm test bar runout is acceptable, then you can start to think about the bearing system.

That is a whole other topic, but in short having all your bearing fits right, orientations and preloads right, obviously using the right spec and quality parts. That will get you a solid spindle so when axial and radial displacement are checked everything is right. Then if you still have movement once installed in the machine you can finally look outside the spindle itself, but Id bet you dont.