SG-250

[WPVT]

I am new to this forum, but not new to sharpening woodworking tools. Several years ago I bought a Tormek Supergrind 2000 from a neighbor when her husband passed away, mostly out of  curiosity. The wheel hub had rusted and split the wheel, so I bought a new SG-250 wheel. The machine is no longer a bargain.
The new wheel worked pretty well when new, but it does not seem to be self-sharpening to any degree. I've tried freshening it up with a diamond dresser, and then with the flat two-sided dresser that Tormek sells, but to no avail. I'm using it on HSS and it simply doesn't seem to cut steel. Curiously enough, the left and right edges of the wheel look fresh, but the center section doesn't. The wheel shape is fine...nothing seems to cause any wear, including the dresser. Could this be a defective wheel ?
As I said, I am not a newbie to this stuff. I've run very precise SWiss tool grinders, old fashioned grindstones, and everything in between. The SG-250 wheel seems very hard, and hence doesn't shed abrasive particles when they dull.

[John Hancock Sr]

I'm using it on HSS and it simply doesn't seem to cut steel

There is your problem. The SG-250 is Aluminium Oxide and softer than HSS. You need a harder abrasive than HSS which would be either Silicon Carbide (the black stone wheel) diamond or CBN. I opted for the diamond wheels and lately threw in an 80G CBN but the Black wheel would also be suitable.

The SG wheel is fine for carbon steel. You average knife, regular chisels and plane blades will be fine but newer harder steels that are now popular will have a herd time on the SG.