Found Collection

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

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.

Les

--
Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.alltel.net/~leswatts/wattsfurniturewp.html
engineering page:
http://www.alltel.net/~leswatts/shop.html
Surplus cnc for sale:
http://www.alltel.net/~leswatts/forsale.html

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.

John

The Atlas manual for the 12" models with Timpken tapered roller
bearings describes how to adjust that and it calls for about .001" of
preload with the spindle and bearings warmed up.  

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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