how sharp for thickness planer knives


rodger.

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Gonna try out my new blade honing jig for my thickness planer knives - how sharp should I go? I need to use sandpaper here, but it l can get crazy high grits.

Online, I've seen people stop at 400 or 600 grit. This doesn't seem near sharp enough, but maybe i am missing something. Any advice?

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I'd probably go to 8000 knowing full well that after you send the first board through it will likely dull the blades back to something like 1000.  Same concept as turning tools...there's no point in going to astronomically high grits because the second that tool touches wood you lose 90% of the sharpness you just labored to achieve.

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I've never honed planer knives past what they come back like, but every time I put a set of knives in a jointer, I hit them on the waterstones, just because the sharpening setup is always ready to go.  The first couple of hundred feet of boards run come out amazingly slick, but it doesn't last that long.  It's also amazingly quiet for a little while.

You do have to be careful handling the knives though, since it's not second nature to realize how sharp they can be.  

 

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I used some PSA sharpening paper (equivalent to 1400, 4000, 8000) and it worked great. 

At first the blades didn't feel super sharp to the touch of my fingers, but they were nice and shiny. I placed them back in the planer and they worked nicely. I did 10 strokes back and forth in each grit.

I didn't want to grind away any significant amount of metal, so I stuck to honing them. I should be able to get a few uses per set, I hope.

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