Fast grinding with water cooling: Does it work?

[Juergen Hannappel]

Hello, when grinding tools the fast grinders with ~2000RPM are usually bas because they overhet the steel, so one goes ond uses slow ones with water cooling. What now if one water cools a fast grinder? Is it possible to dissipate the head well enough to have the steel still cool enough to keep it hard? After all you still have sparks coming off the grinding wheel. Are there besides the mess you create other drwabacks to be considered, such as grindstones not being water resistant?

[Silvan]

Slinging water at high speed at an electric motor that wasn't designed to be exposed to such comes to mind as a potential problem.

I'd say it would not be sufficient just to bathe the wheel in a bowl of water either. The water would heat up, and as it did so, it would be able to carry heat away less and less efficiently. Seems to me if you want to do it fast, you'd need some kind of reservoir and pump mechanism to move a lot of water through, spray it on, capture it, then maybe somehow filter, cool, and recycle it. Or maybe hook it straight to the tap on the supply side, and flush the waste out into the garden or something.

But personally, I hate everything about grinders anyway. I use a belt sander for power work, and follow up by hand.

[Juergen Hannappel]

That's *not* the problem, the spray goes away from the motor.

No. The quickly spinning wheel transports away some of the water which has to be replaced all the time, so it does not really get warm,

[...]

How does the belt sander cope with the heat problem? After all the heat in the steel and not the temperature of the wheel is the problem!

And of course i sharpen by hand, it's rather a question for cases like removing *very* bad nicks in a blade or reshaping a blade completely when several mm of steel have to go.

[Steve Knight]

the belt does get hot. this ruins it faster then the actual grinding alone does. this is why the longer the belt the cooler it grind and the longer it lasts. my 6x48" belt sander runs at 1750 and does fine. my 6x89 runs at 3400 and does fine too. but if you ran that shorter belt at the same speed you would get far more burning.

[GregP]

Maybe you're talking about something else, but I used a powered dual grinding wheel years ago in a car repair shop I worked in where one wheel sat in a water trough. The shape of the trough minimized splashing.

[Phisherman]

I use a cup of water and a small water spray bottle near my grinder. Grind a little, then apply water to the part. I would not put water on the grindstone (use a waterstone instead).

[Ian Wheeler]

High speed grinding is done all the time in metal working shops. Surface grinders, center crinders and centerless grinders all user high speed wheels drenched in coolant to take the heat away (in fact, special coolants - about

97% water with rust inhibitors etc - are made just for grinding). All these types of grinders throw so much coolant around you really can't see the actual part to wheel interface - I don't think you could see what you were doing if you tried to hand hold a part with enough coolant to stop it burning up.

Also, most these grinders take extremely light, controlled cuts - hand holding is not very controlled by these standards.

Ian

[CW]

You will never keep the water on it. In any case, a regular high speed grinder can be used quite effectively to grind plane irons, chisels, ect. That's all I use and never have a problem.

[max]

It is not practical to water cool a high speed grinder. The motor is not sealed against water and it could short out. Grey grinding wheels while water resistant are not waterproof. The resulting sludge is not good for cast iron and steel grinder parts. I like to use white grinding wheels. The cement that holds the wheel together is softer than grey wheels as is the abrasive itself. White wheels are soft enough for the grains to break while you are sharpening. This results in sharper particles cutting faster and therefore cooler. The wheel needs to be dressed more often but it is safer for high carbon steel. You still need to have a bucket of water next to the grinder and continually dip the blade between short grinds. It is not needed for high speed steel which holds it's temper well when hot. max

[ajames54]

I spent most of a Summer operating a Centerless Grinder... 5,500 RPM grinder water cooled designed for turning the grip(shank) on Aerospace quality stainless steel (A286) bolts and screws .. (really boring job)

The biggest issue by far was the fact that the wheels had to be specially designed to operate wet..

1) they had to be uniformly porous or they would go out of balance ( huge issue with a 90 lb wheel turning 5500RPM, probably less an issue for your requirements) 2) they had to use some sort of special composition (sorry I can't remember exactly what) to keep the wheels from turning into mush. 3) They had to constantly be re-dressed because they would clog really fast.

However I could hold tolerances to 0.00025" without ever burning a part.

In short yes it is possible but be sure of your wheel, standard wheels are probably not good enough.