Silicon carbide grinding wheels.

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Hukshawn

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What’s the usual grit for a silicon carbide grinding wheel?

I have an 8” from princess auto (Harbor freight) and I have a seriously hard time grinding carbide. I understand it’s slow going, but we’re talking no going most of the time. I feel that wheel is too fine. It just rubs and polishes and gets the carbide part hhhott, then the wheel loads up. I could be standing there for an hour and not actually take any material off. Makes grinding profiles, or stats least changing the grind on a boring bar a total mess. I used to use a lot of green silicon carbide wheels at an old job, and we chewed through them like hot cakes and they ground carbide very quickly. We would go through 1 or 2 in a shift replacing carbide teeth in surgical needle holders. This wheel doesn’t act the same at all.
 
It sounds like the wheel on your grinder is not a silicon carbide wheel, and is probably aluminum oxide.

If you are planning on having just one silicon carbide wheel, I would think that an 80 grit should be a good all around place to start.
 
I purchased it as a silicon carbide wheel. Its green, soft when I dress it, it will take carbide off, albeit, stupid slow... If it's not actually a silicon carbide wheel, and advertised as such, I will throw it at princess auto....
 
It sounds like it probably is a silicon carbide wheel. When you use it, does the carbide you've sharpened have a shiny, almost polished look to it? If so, the wheel is probably too fine and you should try something more coarse. 60 grit is considered coarse for roughing, 100 and 120 are generally considered proper for finish work.

If you are going to have two wheels, I would get a 60 grit and a 120 grit.

If only one wheel, try an 80 grit. Once you've sharpened something on the grinder, you will need to stone the cutting tool with a fine stone by hand to truly sharpen the edge. I usually finish with a diamond hone after that.
 
Yes the carbide is shiny afterwards. I feel that the wheel is too fine. I'd have to pull the covers off the grinder and probably pull the arbor off to see what grit it actually is. I wouldn't have a problem dedicating that 8 inch grinder to carbide only with a 60 grit wheel and this other one. The other wheel that's on that grinder right now is a fine grit aluminum oxide wheel, it's cheap, and doesn't really do that good of a job either. So I wouldn't miss it much.
 
There you go! Sounds like an excellent plan, and if it were me that is exactly what I would do.
 
Do not buy cheap wheels. Even those green dremel bits cut faster than "green concrete". If you have an emergency, you can just go to the big box store and grab one of those. You can grind a few bits, even chipped ones with that. Then, diamond file to finish.
 
It's an 80 grit from Task... Maybe $29?
It's nice and wide... It was incredibly out of round and unbalanced when I bought it.
Just seems really fine...
IMG_20180223_015136.jpgIMG_20180223_015148.jpg
 
Gray silicon carbide, the green ones are better from everything that I've been told. I've only ever used the green ones myself, so I don't know about the gray ones from personal experience.

Get yourself a green 60 grit for roughing and use the 80 for the fine work and you should be in good shape. You will still need to finish your sharpening with a diamond hone to get them correct. That 80 grit is not as fine as it seems.
 
This is green. The photo didn't pick it up well,
 
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