Using a bench grinder motor for something else?

[CarlosA]

Does anyone see any issue with using a bench grinder motor to power a spindle?

My taig mill motor is about to burn up .. there are signs of melting varnish and strings used in the winding.

I have a nice variable speed Delta bench grinder that would be a fantastic and cheap motor replacement for the small mill. Is there any reason why you just don't see people repurpose cheap grinder motors?

I can easily build the mount, and I'm in a hurry to get this mill back up.


Edit to add the photos and the following text:

I have now disassembled the grinder, redrilled my stock mounting bracket, and made a pully for the 1/8" pitch belt that this machine uses. I opted to go with a single step rather than multiple steps, while fine tuning this setup. I generally ran the mill in the 1000 rpm range anyway.

The optical sensor you see in one of the photos is what the microchip uses to control the speed. I am not entirely sure how it works, but I am assuming it cuts out the power rapidly to lower the speed, this may be an issue on a mill where there isn`t the weight of the grinding wheels to keep it all spinning. On the bench it does work fine. I removed the optical sensor and the motor ran at full speed 3450 rpm.

I`m going to go ahead and attach it to the mill and see how it works, then will fabricate up a box and remote mount all the controls and the start capacitor.

Once it is all dialed in and i`m happy i`ll bandsaw off the excess shafts, and make a cap for the top side, taking into consideration adding a fan inside there, maybe an old alternator fan or something I can find.

 

[Uglydog]

Does rpm and hp meet the prior spec. How about the pulleys and motor shaft?
Will wiring and switches tie in without significant modifications?
Some people are good with making all sorts of electrical changes others flounder. Most of us are somewhere on the learning curve.
Regardless, watch the rpm and hp.

Daryl
MN

 

[CarlosA]

I just made a new pully that will work great. Fortunately because its a bench grinder I can flip it whichever way for the correct rotation. Just have to drill a new bolt pattern in the original mounting plate.

As for electronics .. it seems very simple. It is a variable speed model so it does have some fun ky electronics I know nothing about, but I can easily mount them in a box and attach to the wall next to the machine.

I just wasn`t sure if there was something about a bench grinder that makes it a poor quality motor. I know there is no fan, so duty cycle may be a consideration, on the flip side that also means chips won`t get inside of it.

So a $79 variable speed bench grinder from lowes seems like a great deal and setup compared to a $175 original replacement motor for the mill. And if you really wanted to, you could go to harbor freight and get a bench grinder for $35 after 20% coupon.

 

[Uglydog]

Are the bearings sealed?
Or is it an older model which needs manual oiling.
In Vertical position, you may need to add an elbow to the oil system.

RPM was a huge issue on my Van Norman 6. The old style bearings were evidently not designed to run at high rpms.
Well .... neither are the horizontal cutters.

Daryl
MN

 

[CarlosA]

Are the bearings sealed?
Or is it an older model which needs manual oiling.
In Vertical position, you may need to add an elbow to the oil system.

RPM was a huge issue on my Van Norman 6. The old style bearings were evidently not designed to run at high rpms.
Well .... neither are the horizontal cutters.

Daryl
MN

Yep sealed Chinese bearings, lol

 

[Charles Spencer]

I'd do it. I would consider the fact that I tend to run my mill motor longer and more continuously then my bench grinder. However, an external fan might work. You could probably find one cheap some place.

 

[CarlosA]

I'd do it. I would consider the fact that I tend to run my mill motor longer and more continuously then my bench grinder. However, an external fan might work. You could probably find one cheap some place.

Yep makes sense. I'm sure I could figure out a PC fan setup pretty easily.

And for those who will inevitably suggest a treadmill motor: The reason I'm avoiding that is because I don't really need the range of speed I get out of that setup. My taig lathe does have a nice DC motor setup I did though.

 

[benmychree]

I would only observe that grinder motors are (generally) split phase and have very little starting torque; if this one is a brush type universal motor (being variable speed), this would not apply; I am not familiar with HF cheap grinders, except the larger ones with wobbly wheels and attendant excessive vibration.

 

[whitmore]

I've recently rebuilt my own grinder (an old cheapo Mark1 branded gizmo),
and while the design is surprisingly well engineered for grinding, it is a
terrible replacement for a real motor. The mounting isn't a high-torque-capable
plate, the shaft isn't intended to couple to anything but a wheel and retaining
nut, the stall torque of the motor is undoubtedly inferior... and the shaft
bearings are 'way out near the ends of an elongated housing, and far from the little
rotor in the middle (so it's not mechanically similar to a 'standard'
motor configuration).

Fresh grease after a decade or two, and some attention to the centrifugal
switch contacts, seems to work wonders, though. The bearings were very
light press-fit with one side open and the other shielded.

 

[CarlosA]

So I finished it up the same day I posted all the pics. Finally did some heavy milling yesterday and have had no issues, in fact it seems smoother and quieter than before. It does get warm to the touch, but I think some sort of adapted fan will cure that up easily.