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Post by tntmom on Jan 30, 2011 15:46:25 GMT -5
I know this is probably a "Duh" question, but why can't a grinder exceed 1750 rpm's when doing stone? Is it just an issue of heat or is it something else?
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Post by jakesrocks on Jan 30, 2011 16:46:37 GMT -5
Different types of grinding wheels are designed to run at different speeds. The silicon carbide lapidary wheels were designed to be run at 1725 RPM's. If run much over that speed, you ran the risk of having the wheel fly apart in front of you. I would imagine that the new diamond wheels could be safely run at a higher speed, but most motors that we use for lapidary work turn at 1725 RPM's. Believe me, you don't want to see a grinding wheel explode. I have. The guy in front of the wheel was lucky to be wearing a leather welding jacket at the time, but still ended up with broken ribs and numerous cuts.
The only stupid question is the question that goes un-asked.
Don
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Post by johnjsgems on Jan 30, 2011 20:41:33 GMT -5
What Don said. Also expanding drums are speed rated (2400 for 6", 1800 for 8"). Most wheels have a maximum rated speed for safe operation.
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Post by tntmom on Jan 30, 2011 22:18:18 GMT -5
Thank you! Glad I asked!!!
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Post by jakesrocks on Jan 30, 2011 23:10:35 GMT -5
Glad we could give you an answer. Don't be afraid to ask. Someone on here will be able to answer you. I even learned something new. I didn't know what the rated RPM's were for expando drums.
Don
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Post by johnjsgems on Jan 30, 2011 23:28:13 GMT -5
Not just expandos. I think Novas have speeds designated. Probably any non-solid wheel that could come apart. SC wheels can be used dry faster but I really wouldn't want to use them wet at high speeds.
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Post by jakesrocks on Jan 30, 2011 23:34:51 GMT -5
Guess I just never thought about expando speeds. Just always ran them at 1725.
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Post by Hard Rock Cafe on Jan 31, 2011 12:16:12 GMT -5
Don, I would hate to see an SiC wheel explode. That guy was lucky it didn't take out an eye or some teeth. Yet another reason I'm glad I switched to diamond.
Yes, my expando drums are clearly stamped with a top speed---and don't run them without a belt in place!
Chuck
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Post by jakesrocks on Jan 31, 2011 12:29:35 GMT -5
Hey Chuck, that was a big 12" pedestal grinder for metal. Don't know how many times I told that kid not to grind aluminum on those wheels. Walked in the shop just in time to hear a bang, and see the kid fly across the shop. He was lucky to be alive. It shattered the cast iron guard around the wheel.
Don
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Post by Jack ( Yorkshire) on Feb 1, 2011 3:56:48 GMT -5
Hi I once had a 9" angle grinder disc disintegrate on me nearly winded me I was lucky to have a thick coat on , and that blade was only just over a 1/4" thick , can only imagine the damage a 12" X 1"wheel would do ,
He will take advice from Don & his elders next time im sure
Jack Yorkshire uk
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