Looking for suggestions on carbide tool grinding wheels

[keeena]

I picked up an old Rockwell 23-505 diamond tool grinder and had some general questions about wheel types. I picked this up for grinding lathe HSS and Carbide grinding. In both cases I'm expecting minor clean up and not bulk grinding (I have a regular grinder for that). My general understanding has been:

• Aluminum Oxide for HSS
• Silicone Carbide for HSS (finer grinding) and Carbide
• Diamond for Carbide

...but I'm not too sure on nuances of grits or across the different abrasive types.

What I'd like to know is what sort of wheel styles (types) are preferable and grits would typically be used? I was thinking generally medium or fine would be better suited for what I'm looking to use this for, but not sure. I tried looking up the wheels which came with the grinder to get an idea, but can't find either. I attached a pic of one of the grinder's OEM flange wheels, an adapter for solid abrasive wheels and the 2 grinding wheels it came with.

The green wheel is a Norton 39C100 H8VK. I can't find this exact wheel on their site, but this looks very close: p/n 66252838330 (link). 100 grit. They are billed as a 4" arbor. The center hole is 1-1/4", but the ID of the grinding material itself is 4". So would I normally look up using the latter? Is there a general name for this style with the metal backing plate and 8-hole pattern? I was going to say "cupped", but I thought cupped wheels were much deeper than this type and made entirely of grinding material (no metal back).​

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The aluminum oxide wheel says 7x1x1-1/4, but actually measures 6" in diameter. Why the 1" difference? Mid-west abrasive company, P/N appears to be SFA-6019-VJC (the "1" is hard to read and could be an L? and there could be a space between the 60 and the 1/L). I can't find this part number anywhere and it seems they have been long out of business. Pretty sure its a 60 grit. Is there a general name for this type of wheel which is solid abrasive with the recessed center for face grinding? The edge of this wheel has some serious profile ground into it. I was debating on scrapping it instead of trying to true it. Still worth hanging onto?​

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[Nutfarmer]

I picked up a couple of diamond wheels from Shars for a Baldor grinder and have been happy with them.

 

[Larry42]

The AO wheel probably started out 7" and has been worn away. My limited experience with tool steel or carbide grinding tells me not to go too fine on the wheels. We have a profile grinder for molder knives. To change between the roughing and the finish grinds the same wheel is used but run at a higher rpm for final grind. Flood coolant is used which allows higher rates of removal and better finish. On the Baldor 8" bench grinder some HSS is hand ground using White AO wheels, G or H hardness (fairly soft) and 80 grit. The harder the steel you are grinding the softer the wheel should be. On my single lip tool grinder I mostly use CBN wheels to avoid the grit flying around from using AO. For carbide, diamond wheels, I think they are 320 equivalent. You shouldn't use diamond on HSS as the carbon of the diamond, supposedly, is eaten away by the reaction with the steel. I know that when using "stone" wheels (AO) you need to frequently dress them with a diamond point or a star wheel to maintain shape & expose sharp grit.
Wear a good dust mask when grinding carbide. It contains cobalt which is pretty bad for you.