Nardini Bearing Preload?

I have just finished installing new spindle bearings in my Nardini 12” lathe. Bearings are Timken tapered rollers, front and back. After running the machine for a couple of hours, I measure about .0003 inches end play. The spindle turns free and smooth. The manual is silent about bearing preload or end play.

So my question is should I tighten the bearing some more and run the risk of overtightening. Or just leave it as is?

John

if you are certain there is actually endplay,and not spring somewhere in your measuring system........IMHO,there should be slight drag as the spindle is turned,and the spindle should run warm,but not uncomfortably hot.............nevertheless,if the lathe is producing the desired result in finish and size,.....dont f**** with it.............Generally ,if the spindle is loose ,you will not be able to hold sizes on light cuts.............But be aware taper rollers require enough load to make ALL of the rollers turn on the races,skidding produces flat spots.

The head stock spindle bearings on the Weiler LZ330 are adjusted to achieve a certain temperature rise over a rather prolonged running period. Something like 25C after 45 min , at some RPM. But don't quote me. The instructions I have are in German, and I don't read German. ;-)

Just use this tidbit as an alternative comparison to torque or static friction setting methods. ;-)

How did you replace your bearings I would love to know I have a ms1440 nardini that I replaced the bearings in and have way to much endplay.

First of all you don't tell us those bearings should have zero back-lash on a push from both ends or end play when it is cold. I replaced the bearings on a Japanese 14 40 lathe a few years ago (can't recall the name) and the maintenance manual said zero end play when cold. Then as as John K says this depends on what I call is "lost motion" I use a pry wood or pry metal bar and try to move the spindle and you push by inserting a 2 x4 vertically in the bed rib castings in front of the spindle now and push the spindle using a .0005 or .0001 inch indicator attached to the headstock casting - mag base.


If you mount the mag base on the bed you could be bending and multiplying the error. but you push and watch the indicator, it will move and then you release the pressure and where the indicator stops you zero it. Then go to the back end and push it the other way, I sometime use a chain loop attached to the base and the 2 x 4 inside the loop and push it back. In some lathes I use a pry behind the chuck and casting and again check the lost motion. Leaving it loose when it is warm. How long does it take to run it up to that temp? Do you have to wait to use the lathe to get it up to temp? No.. I use a inflared heat gun (red beam) ...forgot name...(getting old) and if it gets hotter then you can hold your hand on the castings which is around 120 F degree's. no more then 140 F. As John said, don't bend the castings and use that number. Use the lost motion or what's left over after it bends back. Do it a few times with it loose and gradually tighten the thrust bearing spanner nut. Don't use a dead blow hammer as that will make the indicator bounce.