Is It Possible to Slow Down a Grinder's Speed?

[Derek Cohen]

6" at 3450 is 5419ft/m
8" at 1725 is 3613ft/m

That said, I have a slow speed 8", if I were buying again, I would have gone with high speed 6". But if you are afraid of burning the blade, might as well just buy slow speed grinder. It'll do anything high speed grinder will do, just slower.

That is greater than the numbers I have seen before. Did you calculate this? What is the ft/m speed for an 8" wheel at the circumference? This would give perspective to the 6" speed.

Regards from Perth

Derek

[Sam Takeuchi]

That is greater than the numbers I have seen before. Did you calculate this? What is the ft/m speed for an 8" wheel at the circumference? This would give perspective to the 6" speed.

Regards from Perth

Derek

That's already surface speed (hence circumference). From one of my trusty resources.

[Greg R Bradley]

I have virtually no experience grinding woodworking tools, but am a bit familiar with industrial grinding and manufacturing.

8" is the "weird" bench grinder since it is running too fast for many uses. 7" used to be popular where you wanted something more aggresive than 6". 12" is popular as a heavy duty grinder with the same grinding speed as a 6" since they are both 5500sfm.

3450rpm is normal for 6-8"
1725rpm is normal for 10-14"

A 14" normal speed grinder is still running lower surface (grinding) speed than a normal 8".

[Mike Henderson]

As Bill said, a grinder is almost certainly an induction motor and you'd need a VFD to slow that down. Those "router speed control" devices only work with universal motors.

The speeds of 3450RPM and 1725RPM indicate that they are induction motors - a two pole motor for the 3450 and four pole for the 1725. A router speed control would not work on those. Universal motors tend to have much higher RPMs, often about 12,000RPM or higher.

Mike