BadDog wrote:That's good to know (that the CBN and diamond not being so sensitive to speed).
Aluminum oxide and silicon carbide aren't really speed sensitive, but the bonding of each is, and that's the problem.
I'm a bit of a cheapskate, and use wheels until they are literally useless. As they diminish in size, it becomes perfectly obvious that they behave softer, as they slough away faster and faster. And---armed with that idea, it's easy to see why a guy would enjoy a variable speed grinder, as original performance can be easily restored. It's just dangerous, because of the things we've talked about already. I admit, it's a good idea, but the safety factor, for me, overrides any possible gain.
Many have suggested that the smaller wheel won't do much work, as it has lost a lot of surface, but the fact is, it will. If you have any doubt, think of the wheels used for internal grinding, where a wheel may be only 3/4" diameter (or even smaller). They crank up the speed, generally by changing grinding heads (that's how Heald did it), although some machines (like a tool post grinder) offer pulley changes.
And I very much understand and share the concern, but how would that be different than other machines with variable speeds. If you left them at too high a speed for the tooling, disaster and death can be found there as well.
Well, yeah, it can, but it takes a lot more to explode metallic objects, so even if you start a spindle with the wrong speed, it likely will give you plenty of time to shut down. Wheels don't do that. They let go fast and violently. It's not something you need to see to gain respect. But, if you've ever seen what an exploding wheel can do (I have), you don't really want to go there.
Harold