I’m curious what happens to grinding wheels on a microscopic level. Or how stones of different grit or hardness are influencing the cutting tools performance. And maybe other things. So I’ll add here what I think is interesting.

First an example of a common gray 150mm grinding wheel that was glazed after grinding a 10x10mm HSS blank. This is the first tool I made, and it works fine. But it ruined the wheel. Gray stones are useless for HSS. On the left is e picture on the unused side of the stone. The abrasive grains are clear. On the right is the working side.

Next is a 60 grit green stone. I used it many times to grind carbide blazed tools. It is very good. You can’t tell the difference between the side of the wheel (left) and the working end (right). I never had to dress this wheel. I used only once a dressing tool because it was out of round. And I didn’t had a proper truing tool. The trick with green stones is the weak bonding material. It wears out quickly and exposes new abrasive particles. So no chance of glazing. Interestingly they are recommended also for softer materials like aluminium or brass. I suppose they should work fine also for HSS but it would not be economically.

This is a pink fine grit wheel (120) with a closed structure. It is the latest member of my collection and I have high expectation from it. It needs an 12 to 20mm adapter. It should be fine for HRC above 60, so HSS, alloyed steels and so on. I would have preferred a lower hardness than L but that is what I found. The right picture is not pink because of the the bad white balance of my grocery store type microscope.

And last is my Aliexpress dressing tool. It has a few tiny diamonds embedded in that shiny metal