cheap grinder motors - general purpose use?

[CarvedTones]

OK, specifically I am thinking lathe right now as I just got a lathe with no motor yesterday. Tool motors are pricey! Even HF's lowest priced one is $70 and it is only 1/3 HP:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92104
But a 1/2 HP grinder can be found at Big Lots for $20! I have to confess that I have one of those; I got it a few years ago and it is running fine. The wheels are pretty low quality (I am sure you are shocked ), but is there anything wrong with using the motor to power something else, like a lathe? Seems too good to be true, so there probably is a reason...

 

[ptt49er]

Check out ebay, I saw several for pretty cheap there.

I like the idea of using a grinder motor though, I might have to pick up an el cheapo grinder just to tear apart. Off to CL and freecycle I go to search for an old grinder I can trash.

 

[Mike Davis]

Go to an appliance store and pick up a used washer or dryer motor, I see them all the time for $15 - $20. You will have to shield it from the dust. Or try Rehab store and flea markets.

 

[CarvedTones]

Actually, one advantage to the grinders is you don't have to tear them apart, just take a wheel off and put a sheave on. They are already wired and have a power switch. I am referring to bench grinders, in case I confused you.

 

[ptt49er]

Dang, there I go again, making stuff more complicated than it has to be.

And if you ever needed the grinder again you could just slide the sheave off and put the wheel back on, as long as the inner diameters are the same.

 

[CarvedTones]

Rehab used to have them for $5, but they have been a bit more aggressive (most of the time; the lathe was an exception) in pricing and stock less "junk" since the move, or at least that is my impression. I used to have an 40's vintage saw that I got a motor for there. Wiring it was an adventure.

I may have to yank the motor from my dryer; a new set is coming in next week.

EDIT - another reason the grinder is attractive is that it is shielded/enclosed.

 

[ptt49er]

Get it from youy dryer and washer, might was well clean them out if ya can.

 

[CarvedTones]

In this particular case, the lathe has a grinder wheel right on it, which is another thing that made me think about that option.

 

[Travis Porter]

The bearings in the grinder motor are probably not going to hold up very well being tensioned with a belt, but I would think it is worth a try.

 

[junquecol]

The bearings in the grinder motor are probably not going to hold up very well being tensioned with a belt, but I would think it is worth a try.

Most of the grinders that I have fixed over the years, use 6203 bearings, same as on the arbor of a Uni-saw. This is probably the most common bearing in use. Grinders turn at 3450 RPM, while most woodworking machines use a 1725 RPM motor, with table saws being an exception. Give a shout in a couple of days, and I will see what I have in my collection. Unfortunately right now, I'm a very sick puppy, so I can't check for you. Washer dryer motors generally don't have mounting brackets, as they use studs. Also their wires are exposed. Most aren't reversable either.

 

[CarvedTones]

All induction motors are reversable; at least by hand.:rolf:
For those that don't get the joke - don't try this at home - but if you hold one it still when it starts up and then spin it backwards, it will keep going backwards even if it has no claim of reversing.

Good point about the RPM; I would likely end up using a small sheave on the motor and a big one on the lathe with a 3450 RPM motor.

PM me when you are feeling better; I am not far away.

 

[CarvedTones]

I picked up a small sheave; NT stocks 1 small size for 1/2" shafts, though I got the last one in Cary (it's debatable whether spending a couple of extra bucks for a bushing to 5/8" is a better idea anyway; might be in the long run as the sheave would be usable on more motors). I did a few quick tests (pics after I set things up better) and it works but with one major caveat - almost no torque at all. I guess that makes sense; compared to a slow speed 1/2 HP it may have the same power but is in a higher gear. Until you hold something against them, grinder wheels are about as close to frictionless as you can get so very little torque is needed to get them rolling. Anyway, for small pieces of well balanced stock, it works fine as a lathe motor. If you put something big or out of balance on, you have to help it get started.

For my initial small spindle work, this will work. But to answer the question I started the thread with, I have to say "no" - they are not good general purpose motors because of the torque issue. Brand new sealed 1/2 HP induction motors wired to a switch and plug for $25 or so (I think that's what the low end model is at BL). I knew it was too good to be true.