Tool Grinder Wheel/Grit recommendation

[intrepid]

I bought a Harbor freight tool grinder 46727 and other than one wheel, its like new. The PO bought it new and said he only used it a couple times to sharpen lawn mower blade and been setting unused for several years. It has the original green wheels and as stated above one looks unused and the other has some groves in the side. I plan to use this for sharpening HSS lathe bits and also I plan to make a Harold Hall jig for sharpening HSS end mills. I searched many forums for an answer to which wheels but most are asking about carbide grinding and not grit.
What wheels/grit would you recommend for HSS? Hopefully I could use the original wheel for roughing. But, I’m not opposed to replacing both if necessary. I am pretty certain they are 80 grit silicon carbide. But how about a finishing wheel? This grinder has a speed of 3450 RPM.

 

[WobblyHand]

I bought a Harbor freight tool grinder 46727 and other than one wheel, its like new. The PO bought it new and said he only used it a couple times to sharpen lawn mower blade and been setting unused for several years. It has the original green wheels and as stated above one looks unused and the other has some groves in the side. I plan to use this for sharpening HSS lathe bits and also I plan to make a Harold Hall jig for sharpening HSS end mills. I searched many forums for an answer to which wheels but most are asking about carbide grinding and not grit.
What wheels/grit would you recommend for HSS? Hopefully I could use the original wheel for roughing. But, I’m not opposed to replacing both if necessary. I am pretty certain they are 80 grit silicon carbide. But how about a finishing wheel? This grinder has a speed of 3450 RPM.

Something like a Norton white wheel in 60 grit is good for HSS.
Like this: https://www.sharpeningsupplies.com/products/norton-white-grinding-wheel?variant=48626855215406
I didn't shop for price, the link is just to show you the kind of wheel.

I use a wheel like this on my carbide grinder. https://www.nortonabrasives.com/en-us/product/norton-38a-ao-type-02-toolroom-wheel-4
On the other side I use a CBN wheel.

 

[pontiac428]

With corundum wheels, go coarser than you think. 60 white leaves a nice finish, and I like using it, but now I use 46 gray for roughing/shaping lathe tools and often leave that as the finish without going finer. For end mills, 60 is good but I mostly just touch them up with a cheap CBN bonded wheel.

 

[intrepid]

Thanks for the responses. I should have mentioned the grinder uses type 6" Type 50 wheels. I have also had a harder time locating the Type 50 wheels.
So is a white 60 grit wheel for finishing the recommendation? I had been thinking a finer grit for finishing.

 

[pontiac428]

Thanks for the responses. I should have mentioned the grinder uses type 6" Type 50 wheels. I have also had a harder time locating the Type 50 wheels.
So is a white 60 grit wheel for finishing the recommendation? I had been thinking a finer grit for finishing.

The finer the wheel, the more heat it puts into the workpiece. Norton white 60 grit is as fine as you should go for tool grinding, and leaves a mirror finish. In a fixtured grinder, even the 46 grit wheels leave a fine finish, but run a lot cooler in getting there. Heat is the killer with HSS, once it starts to turn blue it softens, so heat control is everything. Unlike sandpaper, the grit doesn't have as much bearing on the finish quality in grinding. It impacts removal efficiency and that impacts heat going into the work.

 

[intrepid]

The finer the wheel, the more heat it puts into the workpiece. Norton white 60 grit is as fine as you should go for tool grinding, and leaves a mirror finish. In a fixtured grinder, even the 46 grit wheels leave a fine finish, but run a lot cooler in getting there. Heat is the killer with HSS, once it starts to turn blue it softens, so heat control is everything. Unlike sandpaper, the grit doesn't have as much bearing on the finish quality in grinding. It impacts removal efficiency and that impacts heat going into the work.

That’s great information and explanation. Yes, I was thinking like sandpaper. I'm always learning. Now if I can find the type 50 white 60 grit. The search is on.
I did find this one at Amazon which I believe is 46 grit. I know of Norton but never heard of CGW.Although my mind keeps telling me to go finer, maybe this may work. Opinions?

 

[woodchucker]

for shaping the tool go coarse, like John says, it runs cooler. CGW, Norton, Radiac all good wheels.
I like the open grain wheels and the white wheels. No problems with the gray either.
The quicker they hog off material the cooler and less heat it imparts to the tooling like John says.

 

[pontiac428]

That’s great information and explanation. Yes, I was thinking like sandpaper. I'm always learning. Now if I can find the type 50 white 60 grit. The search is on.
I did find this one at Amazon which I believe is 46 grit. I know of Norton but never heard of CGW.Although my mind keeps telling me to go finer, maybe this may work. Opinions?

Here you go: https://www.mcmaster.com/products/grinding-wheels/

If you're just going to buy one, get the white 60 grit. If you set up both sides of your grinder, I think you'd be happiest with a 46 and a 60 for lathe tools. If that is your one and only and you plan to do end mills, the 60 grit with a CBN on the other side and the Harold Hall fixture would be a good way to go.

 

[intrepid]

Here you go: https://www.mcmaster.com/products/grinding-wheels/

If you're just going to buy one, get the white 60 grit. If you set up both sides of your grinder, I think you'd be happiest with a 46 and a 60 for lathe tools. If that is your one and only and you plan to do end mills, the 60 grit with a CBN on the other side and the Harold Hall fixture would be a good way to go.

IF, I were to go the route of the white 60 grit and CBN wheel, what grit CBN should I consider?

 

[pontiac428]

IF, I were to go the route of the white 60 grit and CBN wheel, what grit CBN should I consider?

The only experience of CBN that I have is the three Chinese wheels I own, and they vary a bit. I think a high abrasive density wheel matters more than the grit size, so there's that. I use them for mill tools and am not particular about segregating them for carbide or HSS. Stephan Gotteswinter inspired me on those cheap wheels, he says he abuses them and uses them for HSS. So for the last 4 years, I've treated those wheels like Bobby treated Whitney by trying to beat them to death, and they've held up. Mill sharpening is about light and precise cuts and even the Chinese resin bond holds up to that. I have a cup wheel, a lip flare, and an outside lip flare. With some dressing, the 60 grit white outperforms the CBN, but the CBN needs no dressing so it is clean and is tolerant of re-mounting, so that's the main reason I like it.