Correct grinding wheel material for hardened steel?

[knifeaficionado]

There's so many different grinding wheel materials, which one would be the best and most durable to use on hardened stainless steel?

 

[kuraki]

What kind of grinding wheel are you talking about? Almost none of us use grinding wheels to grind knives, with the exception of surface grinding. Start with what you're trying to accomplish and what tools you want to use.

 

[Nathan the Machinist]

There is going to be a "correct" answer to this question, but I don't know it. I do know a rule of thumb with grinding wheels is a hard wheel for soft materials, and a soft wheel for hard materials. You want something fairly friable for hard stainless to reduce heating caused from rubbing with dull abrasive. You probably shouldn't be thinking "durable" you should be thinking "cool".

I've ground plenty of knives on a stone wheel. Not easy, pretty or efficient, but it can be done.

 

[Frank Niro]

Saw mills to plane finish lumber use soft white wheels to sharpen the planer blades.
Frank

 

[Stacy E. Apelt - Bladesmith]

For a wet grinding/sharpening system, there are many choices.
White wheels (vitrified aluminum oxide) run cool.
Blue wheels are harder and are good for sharpening drill bits and lathe tools.
Grey wheels are softer, and work fine.
Waterstone wheels are made of synthetic waterstone material and are fairly soft ... but excel for sharpening knife blades.

The two biggest things are:
A good water film on the wheel. The water should be clean and non-acidic. If using a drip tank, add a teaspoon of baking soda per gallon to raise the Ph. Flow/drip rate should be consistent. You don't want the wheel to swing from wet to dry in quick cycles. Just a millisecond dry can raise the edge temperature enough to damage the temper.
A true wheel. You need a wide diamond dressing tool to keep them that way.

Wheel size determines the amount of hollow grind. Truly flat grinds are difficult on a wheel. The larger the wheel the better.

 

[knifeaficionado]

What kind of grinding wheel are you talking about? Almost none of us use grinding wheels to grind knives, with the exception of surface grinding. Start with what you're trying to accomplish and what tools you want to use.

I mean this type of wheel(maybe slightly larger), below. I would need to make a radius with a norbide stick to create U shaped blade which we discussed before, Kuraki(thanks for the tip):
https://www.bladeforums.com/threads/how-to-sharpen-a-half-moon-shaped-blade.1516049/

 

[Stacy E. Apelt - Bladesmith]

It won't stay a specific size, as it will wear as you grind. You will have to dress it often. For your project, I would use a Norton Blue type K wheel.

 

[knifeaficionado]

It won't stay a specific size, as it will wear as you grind. You will have to dress it often. For your project, I would use a Norton Blue type K wheel.

Thanks for the tip. They come in 1 inch width though, do you think narrowing it down to 22mm would be doable with norbide stick?

 

[Geoff Flato]

You can buy pedestal grinder wheels in narrower widths too. A blue wheel is what you want, but it doesn't necessarily have to be Norton. I always run either CGW or Carborundum they are what my supplier of choice carries. Take a look at machine shop suppliers like KBC and MSC.

A diamond bar would work in place of a norbide stick too. Good diamond bars are expensive but cheap ones work for a while and are under $10
A norbine stick was $60-80 last I looked

 

[knifeaficionado]

Thanks, I think I can order those from USA at least. 1 inch size would be closest to what I'm after, would narrowing it down with norbide stick by 0.05" on each side be doable? It's the first time I'm working with pedestal grinder.

 

[Stacy E. Apelt - Bladesmith]

Yes, you can trim it to a specific size. But, as I said, it will wear smaller. A cheap ebay diamond dressing bar is $10. I would dress the wheel with one of those.

 

[knifeaficionado]

Thanks. What would be the second best choice after the blue grinding wheels? Might be I can't get my hands on those as I'm in europe...

Any opinion on what wheel grit would be enough to finish the blade very sharp without further polishing or sanding?

 

[Geoff Flato]

I'm fairly sure you'd be able to get one there, you'd just have to buy from a company that sells to machine shops.
But if you really can't find a blue wheel, a white wheel would be the next best thing. It would wear faster, but build up less heat than a brown wheel.

And definintly use a diamond bar. A norbide stick well cost at least double what the wheel does, and really isn't worth it for a one off project. If you've seen affordable norbide sticks, they aren't the same thing. The "real" ones are boron nitride, the cheap ones are just a stick of the same stuff a virtrified grinding wheel is made from. At least in Canada a 6" pedestal grinder wheel is around $30, and a proper norbide stick more like $80. A Chinese made diamond bar dresser is about $7

 

[Geoff Flato]

I'll also add that if you're doing what I think you are (something like a cigar cutter?) I'd sooner file it 90% of the way before heat treating, and clean it up with sandpaper wrapped around something round of the right size