# 8520/30 Spindle Run Out Questions



## calstar (Nov 29, 2016)

1)   Head must be trammed for accurate indicating, right?

2)  Does the preload tightness of the lower spindle bearings effect runout?

3)  How much runout do you have on your mill? 

Had another question but forgot, will post when it comes back to me(senior moment).

thanks, Brian


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## Bob Korves (Nov 29, 2016)

calstar said:


> 1) Head must be trammed for accurate indicating, right?


The head must be trammed to help produce accurate work with a good finish.


calstar said:


> 2) Does the preload tightness of the lower spindle bearings effect runout?


Yes.  If the bearings are loose that will produce runout.


calstar said:


> 3) How much runout do you have on your mill?


My Millrite mill is almost new from 1965 and has .0001" runout at the spindle taper.  A milling machine ideally should not have more than .0002" runout.  More runout will cause issues with tool wear and poor finishes, and if the bearings are loose it will cause all kinds of problems, like chipped and broken cutters, heavy chatter and cutter pounding.  My previous Millrite had .0006" spindle taper runout and I found it a problem, but work could certainly be done on that machine.  The 8520/30 is a lighter machine and needs to not be pushed too hard or it will complain...


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