Grinding ID of mill spindle?

I'm not familiar with that particular collet, but if it's not unreasonably long, there's no reason why you can't bore the spindle, using the power feed on the quill. . You'd mount a proper boring tool in your vise and locate the tool so the cutting edge is on center. Size would be controlled by either the table or saddle -- depending on how the tool is oriented. Each thou reading of the dial will remove .002" in a setup like this, so use care. It's not a job for someone that doesn't have much experience, but it damned well can be done, assuming the spindle isn't excessively hard.
I strongly advise you avoid using reamers or other such tools, You have no control over what they do, and are likely to screw up the concentricity of the spindle at the point of alteration.
Harold

And be sure there'll be enough material left after the spindle is bored. The reason the mill uses oddball collets rather than standard B3s could be because there's no room for the larger diameter.
Ned Simmons

snip-----
That would be the best of all worlds, eh?
Nice catch, Ned. I hadn't given that any thought.
Harold

I only need to make a .025" cut, so cutting the spindle in half is probably not an issue. Making the mill a lathe as you suggest sounds like the best bet. Tramming the head to the table with the accuracy required will be a challenge for me.
As far as I can tell, the step is in there to discourage the use of a standard collet.
Thanks for the help. Ill let you know how it goes when I work up the courage to cut (gulp) the mill.
Kevin Gallimore

========= A quick and dirty fix if the spindle is not too hard.
Rig up a verticle boring bar with a carbide tool.
Carefully run the spindle down over the boring bar to cut the step out. You may have to sharpen the carbide tool a few times.
Good luck and let the group know how you make out.
Unk'a George (George McDuffee ===================================
A man may be a tough, concentrated, successful money-maker and never contribute to his country anything more than a horrible example.
A manager may be tough and practical, squeezing out, while the going is good, the last ounce of profit and dividend, and may leave behind him an exhausted industry and a legacy of industrial hatred.
A tough manager may never look outside his own factory walls or be conscious of his partnership in a wider world.
I often wonder what strange cud such men sit chewing when their working days are over, and the accumulating riches of the mind have eluded them.
Robert Menzies (1894-1978), Australian Liberal politician, prime minister.