Spin Grinding Wheel Before Starting

[sierevello]

Anyone ever hear of spinning the grinding wheel several times by hand before starting the surface grinder and making sure that the wheel is still spinning when you start the machine? In the proper direction of course.

Thanks,
Steve

[Harold_V]

The only purpose it would serve is to demonstrate that the wheel runs true, if even that. I generally do spin the wheel, for that reason, and I am not the least bit concerned about which direction it is spun. Wheels are generally not directional. That it must be spun in the same direction it operates is absurd.
I'm assuming that the wheel (any wheel) mounts without issue (no binding on the arbor) and is reasonably parallel, so the flanges grip uniformly. If it must be forced on the arbor, there's a distinct possibility the wheel can crack when the flanges are tightened, if not before. Therefore, one should never force a wheel to get it mounted. If it doesn't mount easily, scrape the bushing until it does. It should be a free fit, to permit the wheel to mount somewhat off vertical, in case the sides are not dead perpendicular with the bore.

Ring the wheel before mounting. That's the most important thing you can do. Hang the wheel on the shank of a screwdriver and give it a light tap with the handle of another. If it doesn't yield a distinct clean and clear ring, break the wheel and discard the remnants. Don't put it back on the shelf, as some unsuspecting individual may mount it and pay with his/her life. If a wheel has a visual crack, that's a no-brainer. Discard by breaking fully, so it can't possibly be mounted.

Don't mount wheels without blotters. Don't over tighten the nut. That serves no purpose and offers an opportunity for the wheel to crack.

Step aside when spooling up the wheel. Give it at least 30 seconds of operation at full speed before you even think of trusting that it won't explode.

H

[John Hasler]

Anyone ever hear of spinning the grinding wheel several times by hand before starting the surface grinder and making sure that the wheel is still spinning when you start the machine? In the proper direction of course.

Thanks,
Steve

The only reason I can think of to do that is that the starter is dead.

[easymike29]

Experienced surface grinder users will spin the wheel by hand in the direction of rotation to help prevent the wheel from slipping on its mount when the motor starts. A VFD, if you have one, prevents this from happening due to its soft start. An instantaneous start will often result in slippage and spoiling of of a freshly dressed form in the wheel.

Gene

[GlennW]

Been spinning the wheel on one of my surface grinders since I have owned it.

I use 8" wheels and it is 3/4 hp. I discovered exactly what is being described in the previous post. Stopping the wheel and re-starting it would render a wheel that no longer ran true due to the adapter slipping on the blotters.

Giving the wheel a quick spin as I hit the start button had solved the issue.

My other grinders are of lower hp and torque and really didn't have too big an issue.

I have looked before and have not been able to find any recommended torque listed anywhere for tightening the wheel adapter to the wheel on wheels with 1 1/4 bore.

My OD grinder swings a 14" wheel with a 5" bore and I did find info recommending bolt torque for the adapter bolts on that though. (two piece adapters that bolt together)

[Harold_V]

In regards to a wheel losing center upon startup, that's a definite sign that flanges are not tightened adequately. Even with a one horse spindle, the wheel shouldn't move upon restarting.

H

[John Hasler]

What sort of motor do you have on that grinder? If it is a capacitor start single phase induction motor putting in the smallest start capacitor that will reliably start it may help.

[GlennW]

Grinders use three phase motors.

[John Hasler]

Motors get replaced. It the machine still has the original motor and controls and the wheel is slipping on startup I think something must be wrong, though.

[GlennW]

Perhaps I led this astray by using the word "slipping", as some appear to be visualizing the adapter spinning in the wheel.

What I am referring to is an immeasurable nearly undetectable pattern in the finish of the part being ground as opposed to the finish of a part ground with a wheel dressed just prior to use.

[John Hasler]

I assumed that by "slipping" you meant that the wheel was changing its position slightly, not that the adapter was actually spinning in the wheel.

[Harold_V]

What I am referring to is an immeasurable nearly undetectable pattern in the finish of the part being ground as opposed to the finish of a part ground with a wheel dressed just prior to use.

It takes almost nothing to create a visual pattern. If memory serves, it has been reported that as little as .00001" (that's ten millionths, folks)!
The same pattern can be created by a dull, or loaded, wheel.

H