I've looked for a long time for something that would flatten the backs of chisels and plane irons. I've found a couple behemoth old three phase horizontal grinders but that's it. I've thought about a surface grinder but they're so s-l-o-w. I once toyed with the idea of the Work Sharp but I wasn't impressed, it appeared to be a quick way to do more harm than good. I've read about the Lap Sharp machine and even discussed it with Don Napels who developed it. I just haven't had much luck with any kind of sand paper sharpening, dubbing seemed inevitable. Besides, the Lap Sharp is pretty expensive.
I flatten a lot of irons and all three of us in the company were facing big runs of plane irons that needed initial flattening at the same time. I called and made sure I could return the Lap Sharp if we had any trouble with dubbing. With assurances we could return the machine if we weren't happy, I ordered one.
It came in last Thursday and I set it up. One of my partners flattened some irons and it seemed to do a pretty good job but the coarse abrasive disk we used didn't adhere as well as I'd like so when I used it today I used a different abrasive. That stuck well and the abrasive seemed to last well. These abrasives stick on interchangeable aluminum disks so changing grits is quick and easy. My problem was that I was getting a lot of dubbing and it didn't make sense. The abrasive Bill used didn't stick as well and gave almost no dubbing. I tried a lot of things and then finally checked the aluminum disk to find it was dished by maybe .015". I had put the abrasive on the concave side and switched it to the convex side. Because these disks are secured in the middle by pressure the disk flattened out and all the dubbing went away.
When I had talked to Don Naples just before ordering, he told me he had recently changed manufacturing processed on those disks. I doubt he knows the new ones are dished. It doesn't seem to be a problem as long as the abrasive is attached to the convex side of the disk. In fact, it may be an advantage to tension the disk on the turntable.
After a period of panic today, I'm pretty amazed by the machine. I think it'll pay for itself quickly. This machine would be a great convenience for most woodworkers but, given it's cost, I think I'd have a hard time justifying it if I didn't flatten so many freshly heat treated plane irons. By the time I finish tomorrow morning, the machine will have flattened 54 plane irons. That's more initial flattening than most woodworkers do in a life-time.