In general the preload would be set to about 5 % of
the max dynamic load rating of the bearing. This is not
so easy to calculate or measure, but a slight drag on
the spindle occurs when it is set to this.
Of course it is always best to check with the manufacturer
if they are still around.
L M Watts Furniture
Tiger, Georgia USA
Surplus cnc for sale:
> Is this by any chance an Atlas/Craftman with tapered
> roller bearings? I used to have one, and when I replaced
> them I seem to remember instructions to run the spindle
> half an hour (to warm it up) then stop and set the nut
> finger tight. After cooling there was a noticable drag
> when hand turning the spindle. Not extreme, but enough
> that it would not freely spin.
> In general the preload would be set to about 5 % of
> the max dynamic load rating of the bearing. This is not
> so easy to calculate or measure, but a slight drag on
> the spindle occurs when it is set to this.
> Of course it is always best to check with the manufacturer
> if they are still around.
> Leslie Watts
> L M Watts Furniture
> Tiger, Georgia USA
> engineering page:
> Surplus cnc for sale:
> > How do you know when the bearings on the spindle are set at the right
> > preload? Also my manual doesn't give a torque spec for the spindle
> > collar. Any suggestions on getting the preload set right? Thanks,
> > Steve
If you know the bearing part number you can get the recommended
preload from the bearing mfgr. The bigger problelm is the
expansion of the spindle shaft when it warms up. The coeficient
of expansion is roughly .000006 in. per inch per degree. So if
the shaft were 20 inches long and after running it to warm it up
say from 70 degrees to 80 degrees. The shaft will "grow" .00012
per degree for a total amount of .0012 inches, loosening up the
preload. Les's advice makes sense but as he said check the
manual if possible, and leep a close eye on the temperature.
The process is as described by Les.
After the warmup, you take all the play out and then advance the
collar 1/32nd of a turn (using the 32 tooth spindle gear the collar
bears on as a reference). Since the spindle has 32 TPI, the advance
or preload would be 1/32nd of 1/32nd or .0009765625 inches.
If it is not an Atlas, this may give you some idea of where to start.
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