Woodcraft Slow Speed Grinder runs VERY HOT

[Doug Olsen]

I just bought a Woodcraft Slow Speed Grinder to sharpen my turning tools. It runs extremely HOT, to the point of being nearly untouchable.

I suspect it isn't normal and if those more knowledgeable than me will please comment, I'll appreciate it.

Do I likely have a defective grinder since it gets so hot in just a few minutes of use?

Thanks very much, Doug

[Rick Potter]

If you are not doing any heavy work on it, and it gets hot, there is a problem. Take it back.

Rick Potter

[Randy Bonella]

2nd that, take it back, somethings wrong. I have one and it runs cool.

If you are not doing any heavy work on it, and it gets hot, there is a problem. Take it back.

Rick Potter

[Doug Olsen]

Hi Rick and Randy,
I just ran the grinder for three minutes and it remained cool, only very very slightly warm. Yesterday I reshaped three turning tools and the grinder was on for several minutes and that is when it got hot.

Perhaps, as Rick suggests, "heavy work" will likely make the grinder get hot and that is what I was doing yesterday. But this morning under what I would consider a "normal" sharpening session of under three minutes, it did not get hot.

Therefore, should I consider it OK if the grinder gets hot when running for several minutes? Thanks guys. Doug

[Don Jarvie]

I bought a Woodcraft grinder and sent it back because one of the wheel covers was damaged. It also vibrated quite a bit. I didn't have it on long enough to notice it get hot. I would have to say it should get warm but not hot to the touch.

I bought the Porter Cable instead but have to get an aftermarket tool rest since the one it comes with has a well for drill bits and not good for moving chisels and plane blades across.

Let us know what you do.

[Jim Neeley]

My woodcraft cheap low-speed grinder also gets hot to the touch after it has been running for a fairly extended (such as an hour) time, the one time I ran it that long.

That it gets hot to the touch does not make it *inherently* bad... as long as it stays within its design temperature range. Cooler motors have larger fans and/or finned heat sinks molded into the case to dissipate the heat... these kinds of things add to the cost of the motor. That's part of the difference between the $99 woodcraft and a $500 Baldor grinder. :)

Jim

[Doug Olsen]

Jim,
You are correct. I took the grinder to Woodcraft to exchange it. There were two more at the store both of which were tested and ran hot after about 15 minutes. So that's three that run hot. The gentleman at the store called Woodcraft HQ, technical department and discussed the three hot running grinders. Tech support acknowledged receiving complaints form other Woodcraft dealers so they took a dozen grinders out of the warehouse and ran them for a protracted period of time. In every case they ran very hot and their conclusion is that it is normal for these slow speed grinders to get quite hot. I'm now convinced that this is inherent in the current crop of grinders offered by Woodcraft and they do not have any ventilation features or cooling fans as you mentioned. Ergo, hot running is the norm and unless it burns up, I won't return it :-).

I took the grinder home and returned it to operation. Thanks for your post. Doug

[Jacob Reverb]

"Too hot to touch"? Eeek...that's probably > 160°F.
My Grizzly T10010 (http://www.grizzly.com/products/10-Wet-Grinder-Kit/T10010) runs cool as a cucumber.

[Andrew Kertesz]

There is a difference between a "Slow Speed Wet Grinder" and the slow speed grinder from Woodcraft. The wet grinders run at 100 - 150 rpm and the slow speed grinder from WC runs at 1750 rpm. Big difference....

[Randy Bonella]

I'll have to see what mine does after running for extended period of time. Usually I run for just a minute or two at most. Also mine is at least 10 years old but looks identical to the one they sell today. I don't think the motor housing is designed like other machines in the shop for extended / continual use. I'll post take a look later today and repost.

[Doug Olsen]

When at the Woodcraft store yesterday we also ran one of the slow speed grinders in their training shop. It stayed completely cool after a 20 minute run time. This is an older grinder, blue in color and yes it looks identical to the current offering except for the color. Over on the AAW forum Mr. Bill Boehme posted an interesting comment and I hope he doesn't mind that I'm pasting it here.



"Well, they might be correct, but their conclusion was not based on a good investigation. More correctly, they should have compared the performance against an older motor and then tried to determine whether a different type of motor was being used if there really was a difference in temperature rise. From what they did, another conclusion could have been that something in manufacturing changed and they were putting out a batch of defective motors.

The nameplate should indicate the NEMA temperature class of the motor and you can find out more about that HERE (http://www.engineeringtoolbox.com/nema-insulation-classes-d_734.html). Based on the temperature rating, the temperature in the column labeled "Allowable Temperature Rise at full load" is what you should go by. Each 10° C rise above that number cuts motor life by 50%.

It could be that they switched to a PSC (permanent split capacitor) motor which tends to run hotter than capacitor start motors. If the manufacturer forgot to do something like put oil in the packing for the bushings (assuming that the motor uses bushings rather than bearings) or that spacers between the rotor and frame create a too tight fit (you could tell if that is a problem by checking to ensure that the shaft spins freely). If the fit is tight then it probably will "wear in" rather than "wear out"."

I believe he makes a valid argument that it is possible Woodcraft may have a batch of defective grinders. There is no name plate on my grinder or the others we ran yesterday so a NEMA rating isn't available but Woodcraft should have this information. It concerns me and I'll watch this thread for more comments but now I suspect these new grinders do indeed have a problem. The store manager also feels they should not run as hot as they do especially after the "shop" grinder ran so cool. The NEMA rating, if applicable to the new grinders, is a little scary if the longevity of the new grinders is affected by heat and their life span is shortened accordingly.

Tuned in for more, Doug

[David Weaver]

If I allow my baldor grinder (not a slow speed grinder) to run for 10 minutes and use it hard, it will also get very warm. I don't know what the housing on your grinder is made of, but I never considered it to be a problem on mine if it gets hot. It'll be a problem if it doesn't turn on sometime, but I don't expect that to ever happen.

[Jim Neeley]

Doug,

Bill gives the technically correct answer. Mine was intended to be at the Readers Digest level I work at when possible.

Hey, I'm a "trying to reform" engineer myself!! :) :) :)

Jim in Alaska

[Bruce Wrenn]

When you say, exactly how hot? 120 degree water is HOT, but most likely your grinder is rated for a higher temp. Remember that because it a TEFC (totally enclosed fan cooled motor) the case is the heat sink. No cooling air flows through motor, and because there is no external fan, the housing becomes hot to the touch. There is even the possibility that there is no internal cooling fan, as grinders seldom run under load for extended time periods.