Wheels from HF are a bArGAin! nah
Type of wheels.. hhmm. When finishing the bevel, started using plain sand discs w/ backing instead of expensive TIGger discs to prevent rounding out the bevel. Anyone else do the same? I truly hate a rounded bevel that sucks, literally.
My favorite wheel is a Challenger II 60 grit from Sait. They're made in Ittly (that's the Texas pronunciation). They smell funny, according to my helpers, and they don't last long, and they don't come cheap. $75 for a box of ten, I think. But they totally rule. They are not for pipe, however. For pipe, I like the Sait blue label wheels. Employers like the red label, because they last longer, but the blue label will get you done faster and easier. Shows you what employers know.
As a general rule there is a trade off in grinding wheels between long life and faster cutting. Harder wheels last longer but don't cut as fast. As long as You are working with plain aluminum oxide abrasives this rule applies. Zircona/aluminum oxide will cut faster at a given wheel life. The designation on grinding wheels [a typical one is "A 24 Q"] begins with a letter to designate the abrasive type. A= aluminum oxide. ZA=zircona/aluminum oxide. C=silicon carbide[use for masonry & cast iron]. The number in the middle, 24 in My example, is the grit size, lower numbers are coarser, just like in sandpaper. The final letter is the hardness of the bonding agents, controlling how fast the wheel breaks down. softer is closer to the beginning of the alphabet, they get harder as You progress through the alphabet, O being softer than R. The wheel has to break down to expose fresh sharp abrasive grains. If it doesn't break down fast enough You can push like all hell but almoast no metal comes off, the work just getts hot.