Grinding planer blades

[Paul Gilbert]

I have a 8" Powermatic jointer, mod 60B. It has straight carbon blades and they were dull so I sharpened them on my newly acquired Tormek T7. This was the first time I have used this grinder for planer blades. I obviously don't have the technique down, because when I put the blades back into the jointer my dial indicator says that I have almost .010 variation along the blade. (humps on the end and a belly in the center of the blade.)

My question is: What is the tolerance to shoot for in trueness of a planer blade?

Thanks,
Paul Gilbert
Dallas, TX

[Jerrimy Snook]

How flat do you want your board? Typically you would want the knife straight, parallel to the back edge, and the same width as the other knives. Of those three parameters. straight would be most critical to the surface finish. You will probably notice a knife variance of .002" when you use the jointer.

[Van Huskey]

I agree with Jerrimy (on this subject not would be stupid). He replied while I was checking a set of knives professionally sharpened jointer knives, they is less than a .001 variation across the width of the 12" blades.

I think the Deulen jig approach produces the easiest and best solution for folks that aren't sharpening blades constantly.