I have some D2 hard steel plastic grinder blades (from China). They were not heat treated when I sharpened them the first time 6 mo. ago. I desided to weld them with D2 rod and see how that worked. They welded funny almost like cast iron (looked like a crater with small glowing puddles around the crater). It stuck well and in the welding process the entire piece got hard (I was hoping it would). Now when we are grinding it small cracks are appearing. We are only taking .001 at a pass and it sounds like .010. We have tried wet grinding and dry. We do not have diamond wheels. Any suggestions on how to not get the cracks, or what is causing them???

D2 needs to be drawn back. Grinding D2 is a nasty process, and a borazon or diamond wheel is preferred. Flood coolant and even then D2 tends to suck into the wheel and warps terribly. How many times have you thrown this part out of the grinder? Even taking .0005 depth and .020 step cuts can have bad results and the load increases and then suddenly the D2 warps into the wheel and is shot out of the machiine. Hated working with it but got the chore as everyone else made sure to shoot their parts out of the machine far more often than mine did. We generally ground to size/profile with soft D2 then hardened/straightend as grinding hard D2 is just a mess.

Nothing like that yet. Just cheep Chinese D2 was not hard when we got it (I could file it with a regular file). Now they are hard but seem to have plenty of cracks, wet or dry. Like my rod was D2 and the parent metal is some type of air hard but not D2. I haven't thrown or broke a wheel yet. Warp isn't bad enough to notice. Any other suggestions.