I haven't had any exposure to using a tool post grinder. It was never taught in the machine shop class I took years ago and there isn't anything in the basic machine text that I have. Can anyone enlighten me on set-up and use with a lathe?
Set up - Do you set the height of the wheel so it's center is the same height as the spindle axisl? Should the shaft of the wheel be parallel to the spindle or angled slightly?
Speeds and feed - What speed do you turn the lathe at? How much feed per pass?
Having the wheel on center is the most desirable condition.
Should the shaft of the wheel be parallel to
That isn't a consideration unless you intend to kiss shoulders. If so, the wheel is best set at perfect right angles to the spindle, with the side of the wheel relieved so only the outer edge makes contact with the shoulder of the part, and by a narrow band only. This should be hand dressed, not diamond dressed, otherwise it will cut very hot. The next best scenario is to set the grinder such that the wheel is angled every so slightly towards the headstock. When grinding a shoulder, though, the wheel will not grind a flat unless you feed it with the cross slide all the way across the shoulder width.. Regardless of the placement of the grinder (wheel angle) be certain to diamond dress the wheel ON CENTER before using it. That yields a grinding surface that is parallel to the lathe ways, exactly what you want.
A WORD OF CAUTION. Toolpost grinders are capable of speeds that can blow up wheels. Don't run the motor until you have made the proper pulley changes for the diameter wheel you intend to run.
Relatively slow speeds, depending on the diameter of the part being ground. A couple hundred RPM's would be plenty, and slightly slower can be useful. Run your part in the opposite direction that the wheel runs, not the same direction. That means you're likely to run your lathe in reverse. It's not fatal if you have to run the same direction, though.
How much feed
Grinding with a tool post grinder is, at best, a PIA. The big problem you're going to experience is heating of the part, a very natural phenomenon, as I'm sure you already know. For that reason, it's wise to take very small passes, perhaps a thou at a time, allowing cooling time between passes. You would be wise to not use any flood type cooling, as much as it is useful. The coolant will spread the swarf to places you hope to keep clean. I'd suggest you plunge the wheel slowly at the shoulder, then move off the part towards the tailstock. That keeps the corner of the wheel sharp instead of breaking down, guaranteeing that the item being ground won't end up with an oversized step on the shoulder end of a part, a result of the wheel breaking down at the point of grinding. If grinding across a piece with no shoulder, direction of feed becomes less critical.
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