Acceptable runout

[Stoney]

I bought a spur drive with a Morse taper and took it to a local machine shop to have the shank ground straight to fit my 3 jaw chuck. I got it back and find the runout varies from approx. .001" to .003". The .001" measurement is on the ground portion of the shank but it is not consistent over the length of the shank that is in the chuck. I am going to take it to another shop I recently had do some work for me and see if they can true it up some. I like this style of driver and wouldn't mind having several ground down from a Morse taper but not if I have to sacrifice accuracy for convenience and ease of use. What would you consider "acceptable" runout for this tool? For the record the TIR of my chuck is <.001" (it is actually better than .001" but my dial indicator only reads in .001" increments so I'm guessing whether it is .005" or .00750" or whatever).

Thanks and regards,
Stoney

 

[RBC]

Stoney,

Are you sure your chuck is dead on?

Scroll chucks are typically only real close at one size. If you expect to be very close at many different sizes, you have to go to collets.

A Set Tru check can be dialed in rather easily, and many will use them so that they can dial in the work when cutting on different size diameters.

Put that spur between centers and see if it has runout then. Or you can chuck up a precision ground steel bar of the same diameter and check that. If you still have the runout, then it is in your chuck.


Royce Bunnell
www.obcues.com