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  #1  
Old 08-02-2006, 06:08 PM
lago lago is offline
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Router Speed Control on grinder

I have the small Ryobi bench grinder and am wondering if a router speed control could be used to slow it down. Thinking about getting a grinding wheel more suitable for sharpening tools.

TIA

Ken
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Old 08-02-2006, 07:36 PM
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LCHIEN LCHIEN is offline
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Quote:
Originally Posted by lago
I have the small Ryobi bench grinder and am wondering if a router speed control could be used to slow it down. Thinking about getting a grinding wheel more suitable for sharpening tools.

TIA

Ken
Most all of those grinders use induction motors.
If the speed is 3400 (most likely) or 1700 RPM (less likely) or thereabouts, it's an induction motor.

Can't use a router speed controller with induction motor, no, no, no!
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  #3  
Old 08-02-2006, 10:53 PM
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You can still use the higher speed to sharpen. The three major problems with a 6" high speed IMO are:

(1) the six inch wheel is more prone to leaving a hollow grind because of the sharper arc...

(2) Most come with the harder grey and courser grit wheels. The white wheel is softer and will tend not to heat up the metal as quickly...

(3) The faster speed will heat you metal quickly and if you stay at the wheel, it will cause your steel to lose temper and you're looking at folded and chipped tips from that point forward.

A solution if you don't want to down-size to a lower and more expensive motor is to slow it down. Touch the metal often and before it gets too hot to keep your finger on it, lie it down and let it cool. When it has, you can come back to it to proceed.

Not a lot you can do about the hollow grind. I don't use the wheel for my hand plane irons or better chisels other than to take a deep nick off the tip. I used to use water stones, but find myself with paper in various grits on a tempered piece of glass. Once you have flattend backs and set the primary angle when you get the tool, touching up is really a snap.

Evening...
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Old 08-02-2006, 11:18 PM
lago lago is offline
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Thanks for your input as that anwsers my question. I knew there was a difference in electrical motors but wasn't sure if a speed control could be used on one.

Ken
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Old 08-04-2006, 03:29 PM
Uncle Hook Uncle Hook is offline
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If the speed is 3400 (most likely) or 1700 RPM (less likely) or thereabouts, it's an

Is there a practical way to reduce the speed of an induction motor?
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Old 08-04-2006, 05:04 PM
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LCHIEN LCHIEN is offline
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Quote:
Originally Posted by Uncle Hook
Is there a practical way to reduce the speed of an induction motor?
Run it on a lower frequency like 50 Hz...

They make AC frequency controllers that provide sinewave power at different frequencies for variable speed work. There's a limited range over whcih they will work.

Grinders have direct drive so changing pulleys or gears is out.
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Old 08-05-2006, 04:11 PM
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LarryG LarryG is offline
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Quote:
Originally Posted by LCHIEN
Grinders have direct drive so changing pulleys or gears is out.
Usually, yes. But this is one of the big advantages of mandrel-style grinders: you can gear the suckers up or down, make 'em run at whatever speed you want. They do take more room, but IMO the ability to change speeds is well worth it. At the moment I have free use of a regular bench grinder but when I get one of my own, I'm going to go with a mandrel style (may even build it myself).
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