Which Grinding Wheel?

[John Hollaway]

For years I've avoided the need to sharpen chisels and plane blades since they had no electrical cord attached. Not any longer. After studying the sharpening lessons of many of the top names, I believe I'm pretty well equipped with the right waterstones, guides, etc, etc. In addition to a set of new bench chisels and several block plane blades, I also need to grind and sharpen a handfull of old, banged-up chisels I've had around for many years. My main remaining question concerns grinding wheels for my 8" hi/low speed bench grinder. What I see available from Norton and others for establishing the initial hollow grind are 36, 60 and 80 grit aluminum oxide wheels. One end of my grinder came with a 120 grit AO on it, but for establishing the initial grind I presume I would need to choose either a 36, 60 or 80. I would appreciated any recommendations. Thanks.

John Hollaway

[Chris Griggs]

36 - coarser wheels grind faster and significantly cooler. You can use a 60 (and plenty of people do), but I have a strong preference for 46 and 36 grit wheels. The coarse scratch pattern doesn't matter since you'll be honing on water stones anyway.

[Bill White]

I would not go any stronger than an 80. I tend to try not getting too aggressive with a bench grinder.
Bill

[Chris Griggs]

First 2 opinions - completely opposite - we need someone to chime in with a tie-breaker vote here, before Bill and I start going at it ;)

[David Weaver]

Coarse. 46 is nice, 36 would be fine. I used an 80 or 100 grit white wheel for a while because it's all I had available locally. I like coarse better, the hollow doesn't have to have a nice finish.

[Jerome Hanby]

Sounds like two good opinions to avoid two different problems. Are you more afraid of eating away more steel than you intended or overheating and drawing the temper?

[Charles Brown]

My $0.02: I like the approach advocated by Rob Cosman. Get as coarse of a wheel as you can, have a good tool rest that can act as a heat sink and only remove as much steel as required. Grinding is just like any other part in the sharpening process; it's a skill that's developed over time and repetitions.

[Chris Griggs]

Sounds like two good opinions to avoid two different problems. Are you more afraid of eating away more steel than you intended or overheating and drawing the temper?

Good point, it may really come down to which you are more worried you will have an issue with. And in either case, paying attention to what one is doing and using a light touch will minimize the chance of each respective error occurring.

[john brenton]

I use the 80 grit grey wheel and just generally avoid going all the way to the edge. If you're going to put a secondary bevel on anyways then there's no point in risking the bluing.

[george wilson]

Use the coarse wheel.

[Dale Cruea]

I like a coarse wheel. The one that came with my grinder. Not too sure what the grit is but is seems a little too fine. At work we used white and pink. I liked the pink a little better as it did not burn as readily.
I would like to try the blue wheels from Norton I think it is. I burn everything up with a gray wheel. They don't seem to break down and just load up on tool steel. They are OK if you keep them cleaned and have a light touch. I don't.
Anyway, I like something lower than 80 grit. About everything I have read calls for a 36 grit.

[John Hollaway]

Use the coarse wheel.

So George, which grit are you calling coarse?

[george wilson]

I recommend the 36 grit for coolest grinding. Learn to use a light touch. It isn't difficult.

[James Taglienti]

I use a white wheel... But when that wears out i am going back to a coarse gray. The white claims to run cooler, but i don't see it.

I just can't see any tool rest acting as a sufficient enough heat sink to prevent burning the tip of a chisel... The wafer thin edge of the tool heats up so fast there wouldnt be time to channel the heat into an already warm rest.

The only way i know how to do it is quench. I know some people say it changes the temper, but I havent seen it. When i quench, there it usually a bead of water sitting on the tool when it goes back to the grinder. As soon as that bead evaporates, i quench again. There's my heat sink.

[george wilson]

I quench when the wet edge dries up-instantly!!.

I'll NEVER go back to the old gray wheels. The white ones are SO much better. Sorry you can't see it,James.