I have an old Craftsman 6″ grinder – 1/3 HP I believe. It only runs at 3450 RPM. I would like to reduce the speed and change over to the white wheels. Is it OK to use a router speed control? Since the grunder has an induction motor and routers used universal motors, I didn’t know if this would work without damaging the motor or the control. Or is there a speed control made for induction motors? I don’t know much about electrical motors. Maybe there is a way to rewire the motor?
Your input would be appreciated.
Replies
Dan: Can't rewire the motor, it is what it is. Try this link: http://web5.automationdirect.com/adc/Overview/Catalog/AC_Drives_-z-_Motors?source=msn
or do a search for "motor control" and you will get many choices. The only way it might be worth buying a controller is if you can buy a bare board and put it in an enclosure and connect it yourself. Otherwise it might cost as much as a new, lower speed unit.
Duke
"... Buy the best and only cry once.........
Motor controls of the type you sent the link to only work on three phase motors, so far as I know, a standard single phase induction motor can't be slowed down.
John W.
John: I'm not sure, I was wrong on the link I posted but I'll look more. I retired after thirty years as an industrial electrician, most of my motors were large to gigantic, only a few had speed controllers of any kind. It may be that the 3 phase output units can run with single phase motors, with a tweeking of a dip switch on the board. I will look into it. Duke"... Buy the best and only cry once.........
Duke,
The basic problem with single phase induction motors, is that they all have centrifugal switches for starting. If you throttle them down, the switch will kick in and burn up the starter windings in short order. I believe there are a few other technical problems with slowing down a single phase motor but the switch problem is a show stopper.
John W.
John: Ya know I never thought about it that way. The starting switch wouldn't reclose that soon if you dropped the speed only to a reasonable level. I think you are probably right about no speed controls for single phase induction motors. If I find one I'll get back to you. Duke"... Buy the best and only cry once.........
Like Duke says...can't use a speed control. You should learn to take a light touch instead. Also add a water mister. A simple gravity fed drip coolant is pretty cheap...like free with a gallon jug hose and clothespin drip regulator.
Well according to everyone, you can't slow the grinder down. So, learn to use light feed pressure and other good technique. I have the white wheel on my fast grinder and to my knowledge I haven't burned an edge in many years. You need a good wheel dresser to keep the face of the wheel clean and sharp. The faster it cuts, that is, the easier it cuts then the less the heat build is.
Another thing to keep in mind. If you ding an edge and have to grind a good deal to get it out, it is good practice to simply push the iron straight into the wheel and quickly grind out the ding. Then, set your angle and grind the bevel. By doing it this way, you have more steel out at the leading end of the iron. More steel means more heat absorbing capacity (Did I use proper terms there?) and you'll be less likely to "burn" the edge. The iron is most likely to overheat and burn when you are just about finished. So you must force yourself to go slow (very slow) right at the end when you are already bored with the whole process.
Be one with the steel. Breath deep. Quench often. Have a drink yourself........(a drink of water, of course)
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