A week ago, I bought a spare set of jointer knives because my original set
needs sharpening. The old knives were leaving lines on the material and not
cutting well. The new knives were just in time to straighten some soft
maple for cabinet doors. The new knives are made by Amana.

Here's what surprised me...for the first 10 boards, the cuts were smooth as
silk. I kept checking each one in amazement as to how perfect they were
coming out. Then, without realizing it, I guess I passed a board with a
small knot over the surface. After finishing the rest of the boards, the
remaining few started to show signs of knife divots, etc. I barely used
them for 30 minutes and now they're leaving knife marks (sandable but less
than perfect) on the material.

How long should freshly-sharpened knives remain "perfect" until they start
leaving some marks? Also, how many times can jointer knives (I have a
3-knife 8" jointer) be sharpened? Can a tougher knife be purchased for
jointers, something with carbide, perhaps?

30 minutes of bliss and now it's back to reality.

-m