how sharp should jointer knives be?

[Tim Sherwood]

I'm changing the knives in my planer. The old ones had too many knicks. I bought a set from a big name blade company. When I openned the package, I was disappointed with the coarse grinder marks they showed. The backs especially looked like they were too rough to be really sharp. They look just like most chisels do straight from the factory. I expect to have to finish the sharpening job on those. But I thought jointer knives were ready to go? I've seen a lot of discussion advising against trying to sharpen these knives at home. Am I looking for unreasonably sharp blades?

 

[Roy G]

Tim, can you cut paper with the knives? They may be sharp but not finely finished.

Roy G

 

[Tim Sherwood]

No Roy, they will not cut paper. The grinding on the bevel is certainly better than the back. But I can feel it drag against a fingernail. I will say that there was a small wire edge on the back. They seem to be sharpened at a 35% angle.
I changed the disposable knives in my benchtop planer yesterday and they were much sharper than these jointer knives.

 

[Mike Davis]

I sharpen my 12 inch planer blades on diamond stones. Keep the back flat against the stone and work it in circles. Go up through the grits just like a hand plane blade.

You could make a wood jig to hold the blade angle for the bevel but I do mine by hand. It takes me about 10 minutes per blade, 45 minutes total from loosening the first bolt to turning it back on. I can’t drive to town in that time to buy a set or drop one off for sharpening.

I have demonstrated sharpening and resetting jointer blades at Bill’s shop and at the Midwest picnic. Yes, you could mess up, but that is usually easily corrected.

Never put them on a bench grinder. Very few people have the skill to successfully grind jointer and planer blades by hand.


oh, the answer to your first question; how smooth do you want your wood?

 

[Tim Sherwood]

Thanks Mike .I'm at least going to lap the backs. I still have a question about whether this is to be expected with "quality" knives?

 

[Mike Davis]

Thanks Mike .I'm at least going to lap the backs. I still have a question about whether this is to be expected with "quality" knives?

No, good knives will be smooth and sharp. I usually buy from global, but I forget the full name right now.

 

[FredP]

No, good knives will be smooth and sharp. I usually buy from global, but I forget the full name right now.

Globaltooling.com?

 

[Mike Davis]

Globaltooling.com?

Yes, always had good service and best price there.