Spindle nose questions

[Suzuki4evr]

I have two questions for the experts out there and it is merely for information sake,about lathe spindle nose cones and chuck backplate registration on the nose cone.

Say you make a new backplate, do you need to make it that the backplate register on the cone and flush up against the back of the spindle? Because it could be pretty difficult to get it to mate against the cone and spindle plate at precisely the same time. My head tells that that is the way it should be and that is the way I did a few years ago for my new chuck, but with a lot of fitting and removing the backplate.

Secondly, if the Spindle nose is a bit worn or damaged, is it advisable to regrind it on the lathe using a TPG or some grinding device before making a new backplate?

Food for thought.

Michael

 

[markba633csi]

If you are referring to tapered spindle noses then yes I believe there is no shortcut to a lot of fitting and removing, unfortunately
-Mark

 

[RJSakowski]

Simultaneous registration on a conical surface and a flat surface perpendicular to the axis of the cone is an over constrained system. There are three possible cases: the mating part seats on the conical surface first, the part contacts the the flat first, or it contacts both surfaces simultaneously. Given that in any machining operation, tolerances are at play, the latter is unlikely to exist. If the second case were true, the re would be a small amount of clearance at the conical surface which would potentially cause problems with proper radial registration. However, if the first case were true, the part would seat on the conical surface providing proper control of radial runout. Tightening the assembly would very slightly deform one or both of the conical faces while drawing the part tight to the flat face.

Therefore, I would think that the best case scenario would be the first case with a very small clearance between the flat faces.