Converting to variable speed.

B

Brett Bennett

Joined
Dec 14, 1999
Messages
672
I would like to convert my 1hp grinder to variable speed and am looking for information. Has anyone accomplished this? Is it cost effective (ie., would it be cheaper to buy a variable speed motor?). If this idea is a bust, I will probably go with a pillow block and tapered mandrel setup. TIA.


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None are more hopelessly enslaved than those who falsely believe they are free. -Goethe
 
Tom,

I have the K&G catalogue. I forgot about them (all the triple digit prices on that page scared me away!) They list a few controllers in the range of $160. Is that all that is required, other than hooking it up? Anyone know of any that are less expensive (without sacrificing power)? Thanks.

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None are more hopelessly enslaved than those who falsely believe they are free. -Goethe
 
I have often thought about trying to convert to variable speed also. pricecutter.com has a router speed control unit on sale for 29.99
It states that it can be used for single speed routers with brush style motors up to 3 1/4 horse or 115v/15amps. it also states not for use with soft start motors. i am not familiar with that term, is a grinder motor soft start? If not, i would think it would work. Any body know for sure?

[This message has been edited by ydduit (edited 02-10-2000).]
 
Just did some reserch on this a couple of day's ago.
Guy's stay away from router speed controlls, this will damage your AC motor. It has something to do with the start windings trying to kick in at the lower speeds.
The only way to go is a 1 1/2 HP DC motor with a speed controll, or a variable frequency drive. Either way is expensive, frequency drives are a overkill for a grinder.

Thomas

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Haslinger Handcrafted Custom Knives
http://members.home.net/thknives
thknives@home.com
 
Kaos I just converted my Burr King.It took a little help from a couple of knife making freinds.

My Parts list:
Baldor BC 143 Heat sink
Baldor BC 141 DC control
Baldor BR0006 Resister
Browning AS30x3/4 pulley
General Elertric 100vdc 1.25 hp DC motor
I went to Lowe's and got a cord,an fuse box to mount the controler an heat sink to.
the motor will have to have the key way slot cut the whole length of the shaft. The motor number is 10-1485-A purchased from Surplus Center @ 1-800-488-3407. I have this set on 115 volts. You will have to adjust the speed and torque but it easy.
I thought about buying the complete kit from K & G but this was cheaper and what i saved i was able to buy a Sears floor type drill press. It has been working fine with no complaints. I spent $354.00 to convert. If i can help any more let me know.

[This message has been edited by RDF (edited 02-10-2000).]

[This message has been edited by RDF (edited 02-10-2000).]
 
Thanks for the information. It's a shame this much fun is so expensive.

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None are more hopelessly enslaved than those who falsely believe they are free. -Goethe
 
The router control doesn't work on most motors.One thing it and a router and a bunch of the rubber drum sanding sleeves do is make a usable sander for small cut outs.
Like finger grooves. mount your router on a router table. You can also finish profiling your blades this way.
Take Care
TJ Smith
 
its not just a matter of converting a motor. ac motors on reostates have NO torque at low end....dc motors have the same amount at ALL speeds....that, in my opinion is THE bottom line....what good is it to have your motor go 30 percent speed if you can stop it by pushing on it....i can turn my motor down to 18 percent and LEAN on it....save your money, by a dc motor and controller...a good one...Ive had mine for about 16 years and its still going strong...that works out to about $38 per year.....so far...i have dc variables on my disc sander, metal cutting bandsaw, and my 10" south bend...

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http://www.mayoknives.com


 
Former (and always) industrial electrician here.
As posted, only a permanant magnet DC motor has the ability to control torque at a lower speed setting. DC brush motors without magnets (shunt-wound) do not, so they will stall at low speeds with work load.
Check carefully the controller for the motor. Make sure it's rated for the specific motor. Only the better ones have torque adjustments as well as min/max speed, ramp up time, coast delays, etc. It isn't simple anymore, boys.
A very nice feature is a dynamic braking resistor. No coast time, it turns the motor into a generator when you hit "stop" and chokes the speed right out of it. Great for speedy belt changes...

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Jay
www.gilanet.com/JayFisher/index.htm
 
thanks jay...we need more guys like you on here who have the FACTS....everyone wants to save money...but in the long run buying the best is really the most economical (have a hard core grinder on order-$500 left to pay)

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http://www.mayoknives.com


 
I must agree with Tom and Jay as far as the motors and controllers are concerned.

The only "economical" method of a pseudo-variable speed setup would be to have different pulleys or sheaves, as a drill press uses. This leaves a lot to be desired but it can be done. Bear in mind that changing speeds is a major pain in the behonkus but it will work. It just depends on how much you are willing to put up with to get there.

But to get the thing to turn slow enough....that may be another story.

C Wilkins
 
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