Strange uses for tool post grinder

[Weston Bye]

nheng
Check out my article in the Sept/Oct 2004 HSM, "Machining a Spiral Cam".

Lacking a tool post grinder, I made do with a wheel mounted on a sewing machine motor. I borrowed the compound slide from my Atlas lathe and mounted the cam to be ground, on the shaft of a stepper motor. The grinding wheel turned at right angles to the cam so as not to overcome the holding torque of the stepper motor. The spiral cam produced 0.1mm increase/decrease in diameter for each step of the stepper motor. A 100 step/rev motor would provide a lift of 10mm to the cam follower.

Since the article, I did the same operation with a Sherline mill by rotating the spindle head 90° with a grinding wheel mounted on an arbor and held in the spindle, and holding the stepper motor with the shaft vertical in the milling vise. All the usual steps were taken to protect the ways and leadscrews from dust and grit.
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Weston Bye
Grand Blanc, MI

[nheng]

Has anyone ever rigged up a tool post grinder on a mill or lathe to do some minimal surface grinding? How'd it go?

[darryl]

I find that my homemade T/P grinder will get me to a certain level of smoothness and no more. It's built using 1x2 aluminum block, and is quite rigid, but the limitations are obvious. It seems to be a function of rigidity and vibration. If I did this over again, (rebuilding it) I would probably look for a smoother version of the ball bearings, and pay more attention to the balancing of the motor armature, and the grinding wheel itself. One thing to consider whichever way it's mounted, in which direction will the setup be flexing when the wheel encounters the workpiece. If the wheel is brought towards the workpiece, (similar to climb milling) it will tend to dig, then release, etc, making for a poor finish. If the setup flexes such that the wheel is taken away from the workpiece, same result, though not as bad. Try to set it up such that any flex is along the plane of the surface you're working on. Aside from the level of surface smoothness attainable, my worst fear is the damage I could be doing from the swarf.

[nheng]

I think I may need to clarify a bit.

Were you grinding a flat surface and if so, how did you mount and position the grinder?

[ibewgypsie]

Off on a tangent..

BUT, have you saw a grinder mounted on a very old shaper? they make a surface grinder from Hades..



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David Cofer, Of:
Tunnel Hill, North Georgia

[Alistair Hosie]

Dave are you coming to Scotland anytime soon ?Alistair

[nheng]

Ibewgypsie, I'll bet they do. To even consider using a TPG, seems like you'd have to develop a pretty fast traverse capability.

On small parts though, the table feed on a mill ought to be fast enough for light cuts, no?

[beckley23]

I have 2 surface grinders, a 6 X 18 Norton, and a 8 X 24 B&S, both grinders have hydrualic feeds. The Norton top speed is about 30 FPM, and the B&S is 60 FPM. I generally run the machines as fast as they will go. On mills the feeds are in IPM.
Harry