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Abrasives 101

I am getting a mini-lathe and eventually will be shaping and sharpening tools so I searched the web for info on grinding wheels but have some confusion.

Please fill in and correct.

I have a 5" grinder with coarse and fine GRAY wheels, I think that is Aluminum Oxide and is good for HSS.

5" Aluminum Oxide wheels are difficult to find let alone any other abrasive type. If you know a source, please share.

For sharpening Carbide Tools I need a Silicon Carbide wheel which is GREEN. Right? I read that Silicon Carbide is not indicated for ferrous material. I have used a flat Green stone to sharpen wood cutting chisels and plane irons for years. Either is OK for steel or green does not necessarily equate to Silicon Carbide.

I see BRICK RED stones, often used for wet grinding of wood cutting tools, usually finer that the GREEN stones. What material is that? What is it best for?

I also see wheels WHITE in color that looks like made of sugar cubes, what material is that? What is it best for?

I summary I like to be able to associate color and material assuming that is possible and for each type of tool material what is the proper grinding stone.

Also, HSS should be honed with a diamond hone. I have seen diamond hones in the shape of blocks which seem impractical to rub the tool on the block rather than have a hone similar to a file that you move on a fixed tool. What do you use for this?

An then there are the ceramic...

Thank you for your help.

Mauro Gaetano

Reply to
MG
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A 5" bench grinder is likely to be a complete misery. My first suggestion is that you scrap it and get an 8" one on your local craigslist. Bench grinders are ubiquitous and dirt cheap. Make certain you see it run and that it runs smoothly and that it comes with all of its parts. Actually, try to find a grinder with a

5/8" shaft instead of a 1/2" shaft. That will likely rule out the tiny ones.

A gray wheel is likely a very hard aluminum oxide wheel. Yes, AlOx is suitable for tool steels. However, the first thing to learn in Abrasives 101 is for soft metals you need a hard wheel and for hard metals you need a soft wheel. HSS is hard, and so you need softer wheels.

Grinding wheels are really cheap. MSC, Enco, J&L, places like that.

Right. I have had a home shop since the mid-'80s and have yet to need to sharpen carbide, however. I use some carbide tooling, but it's either indexable inserts or brazed carbide bits I got for nothing and if they go bad I toss 'em. I suggest you forget sharpening carbide until and unless you have a real need.

A hand stone? Who knows what it is?

??

Probably aluminum oxide again.

Call MSC and ask them to send you a Norton catalog. Or just google on grinding wheels, jeez, in ten seconds you should find everything you want.

I disagree again, sorry. Diamonds, being carbon, dissolve readily into steel. I use Gesswein hand stones, Washita stones, Arkansas stones and the like for hand honing.

Kudos to you for asking. That's how you learn!

GWE

Reply to
Grant Erwin

You want a diamond wheel. $$$ Green wheels are a distant second place. But nothing else even finished.

Reply to
Richard J Kinch

The wheel that goes on the Twice as Sharp scissor grinder is a 5" I hardness 100 grit . Order one from Wolff industries it's a pretty good all around wheel for steel small tools. As for green or silicon carbide it will shape a carbide tool but you still need to follow up with diamond.

Reply to
bamboo

According to MG :

I see signs of three followups, but they have vanished from my news server, so I don't know what they said.

Hmm ... 5" is pretty close to 125 mm. Is it possible that the grinder is from some European or Asian source? If so, you may have to go there to get some in the sizes which you need.

The alternative might be to find someone who has a 6" grinder, and get the stones which he is replacing because he has worn them down to 5" size.

It works -- but not very well. Just better than the gray stones. For sharpening tungsten carbide, I believe that diamond is the ideal choice. (But *don't* use it on steel.

And when grinding carbides, be careful to wear breathing protectors, as the grinding dust tends to be somewhat toxic.

By hand, or power? What I understand is that the green stones are softer than others, so the binder crumbles away, exposing new edges of the Silicon Carbide for working on the Tungsten Carbide tool material.

Not sure here. I use tiny green stones for tuning concertina reeds.

I don't know -- but I'll bet that it runs a lot slower than the normal stones.

Here is where we need input from Harold. (He may have been one of those who replied already -- I hope so.)

A *hone* maybe -- run at very slow hand powered speeds. However, a diamond should *not* be used under power on any ferrous material, including HSS. The steel tends to eat the diamonds (converting the steel to even higher carbon steel).

I actually use the white wheels for grinding HSS bits to special shapes on my surface grinder.

You'll need more than I can supply, so I hope that others have supplied good information.

Enjoy, DoN.

Reply to
DoN. Nichols

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