heat controlled bench grinder

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Barmaley

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Dec 31, 2016
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The problem with bench grinders is that they overheat the blades. What about of using the grinders at a very slow speed similar to the hand sharpening speed so the steel will stay cool?
 
Barmaley said:
The problem with bench grinders is that they overheat the blades. What about of using the grinders at a very slow speed similar to the hand sharpening speed so the steel will stay cool?
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The first thing that came to my mind was that you'd go from overheating the blade to overheating the motor. It's an easy explanation for motors with fans attached- you won't be pulling enough air through the motor to keep it cool, but the actual reason that more heat is generated at low RPMs probably has to do with efficiency curves and motors only being designed to run within a certain window of speeds!
 
To avoid an electrical discussion I would say that electrical motors the area of my professional expertise. You are correct that if you somehow make a motor designed for a high speed to operate at a low speed you are looking for multiple trouble. Nevertheless there are motors specially designed for a slow rotation, in addition we may use a reduction gear. The second solution would be to use a low diameter stone - a ceramic rod comes to mind. My thinking goes around the fact that is 21 century muscle power could be reduce to leave the operator to do more complicated work. I also think what a machine sharpener could make it easier to control sharpening angle. Possible it may speed up the process if it will be found that the velocity if the contact could be increased several times without heat problems. Probably it is a crazy idea but I think may be somebody tried that before and can tell us why exactly it will not work?
 
Yep, they exist. A Tormek is a slow speed grinder. You can also buy slow speed bench grinders or stick a vfd on a motor for speed control.

wet grinding is another way to keep heat down.
 
My grandfather had a small bench grinder that had a water trough that soaked the wheels as it ran.
 
Sure, low speed will work. A stream or trough of water seems more popular.
Rig up an arm and a squeeze bottle, make sure the angle is right.

What/how much are you sharpening that you need a grinder?
 
You might try CBN wheels - ideally on a 1750rpm grinder not the higher speeds. No need for water or other cooling. Do some google but here for an intro from a blog ~

" First, CBN stands for Cubic Boron Nitride. It is an abrasive material. The only thing harder than it that I know if is diamond. There are both diamond and CBN wheels available for sharpening purposes. The diamond wheels are fine for carbide, glass, and ceramics, but don't handle heat well when used to sharpen the hardened steels like we use for our turning tools. CBN is ideally suited for any hardened steels as there is little heat build up, so breakdown of the abrasive is very minimal."
 
So, just got a Worksharp Ken Onion, and run it at low speed with a factory spec. of 1200sfm. I am getting little heat on edge by feel, the motor housing gets hot by feel. I have some small fans to carry heat away for the motor. My other thought was slowing down the motor with a 50 buck Variable Frequency Drive from the bay (for the sake of motor, and knife edge as secondary gain). Tormek's run like, not sure but maybe ~175 rpm.
For the edge, a plate with a wet sponge works. But I found some water proof belts for the grinder attachment, which means the knife can get misted by hand if I place a silicon dental dam barrier between the grinder n motor assembly. Grinder assembly is casting and all parts attached can be cleaned and lubed / maintained appropriately.
What do you think?
motor spec-
Variac Transformer Variable 500VA AC Voltage Regulator Metered 0-130V 110V with one AC outlet built in.
 
Beeswax is the cheapest and easiest way to help control heat on bench grinder stones use to sharpen knives.

Just rub the beeswax to the stone while running or while stationary then the stone would not generate heat, it would also cut slower and finer than stated grit,

It would work similarly to those paper wheels with grits on.
 
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if you're burning up blades on grinders you ain't doing it right, no matter what speed you run at. Paper wheels, properly bound cloth wheels and buffing will give the results you want. Putting wax on a wheel of any type will just slow down the whole process and defeat the purpose of using powered tools. waxes and buffing compound work best on buffing wheels for finish, but not well when trying to sharpen.
 
SOLEIL said:
............waxes and buffing compound work best on buffing wheels for finish, but not well when trying to sharpen.
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Arent paper wheels with SiC also calls for use of wax to help cool blades and prolong life?
worked the same on SiC stones.
 
not to my knowledge, but i don't know very much. even if they did i wouldn't do it. i hate clogging up my sharpening medias with anything that's hard to remove. i don't worry about heat and have never ruined a blade after enough practice to learn the right way to do it. my right way may not be yours, ymmv.
 
You could build a grinder,belt if preferred, and start with a 1200 rpm motor,add a vfd drive,but how much money are you going to spend?
 
scottc3 said:
if I place a silicon dental dam barrier between the grinder n motor assembly. Grinder assembly is casting and all parts attached can be cleaned and lubed / maintained appropriately.
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Hi, have you been able to assemble the dam barrier? any photos to share please?
 
Do a search for "water cooled grinder". We had a water cooled grinder in the high school wood shop for sharpening chisels and plane blades.
 
There are three or four companies selling Tormek knockoffs for about half the price of the genuine McCoy.
 
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