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Sharpening Jointer Knives

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jointer jointer knives sharpening
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20K views 17 replies 13 participants last post by  SASmith  
C
#1 · (Edited by Moderator)
Has anyone ever tried sharpening Jointer knives?
I've been using my jointer a lot for the past year and its' getting to be a hassle (not to mention expensive) to send the knives out to be sharpened.
I sharpen all my own chisels, gouges and planes so I'm thinking about purchasing a few 10" DMT diamond stones and having a go at sharpening the jointer knives myself. Has anyone ever tried this? Any tips or useful jigs? Or is it better to go with a sharpening service?
 
#2 ·
I usually take mine out and sharpen them by hand, running the edge over wet sandpaper thru the grits on marble. I don't use a guide or anything, I just do it by feel. I've never had any complaints about doing it this way. I sharpen my planer blades the same way.
 
#4 ·
- Measure the bevel angle on your knives,
- cut a bevel on a piece of wood with that same angle,
- lay the top of the knife against the block so that the knife bevel is down,
- put the block and knife on a flat piece of sand paper or a stone,
- slide the knife back and forth.

Works pretty well to restore a sharp edge. It's not depth referenced side to side so I dont think I'd recommend it for regrinding a bevel or taking out large dings, but for very quickly and easily touching up an edge it is super fast, cheap, and easy.
 
#7 ·
I've never done this but saw an article or something years ago not real long after buying my PM54. But somebody had a method for doing them while still in the cutter head. I cant recall what they were doing to lock the head position but I think they were adjusting the infeed table so that the knives stuck up pretty far, removed the fence, and put something thin and flat on the table to protect it, then ran a stone back and forth along the knives. Seemed like it might be a decent method and ensure the knife heights didn't change but like I say, I never tried it.
 
#8 ·
Actually the Powermatic owners manual has a method similar to the one DougS. mentioned, except you don't lock the cutter head, you level the infeed and outfeed tables, then turn the machine on and slide the sharpening stone across the blades. It will sharpen them, but it's kind of scary doing it. Takes a real light touch or you'll take the blades down to far. I have a Grizzly plane blade grinder that I use for my jointer and planer blades.
 
C
#10 ·
Thanks again for the responses. This is what I ended up doing:
I first got a 6 1/8" x 6" piece of walnut. (the blades are 6 1/8" long)
I found the angle of the blade using an angle gauge.
I transfered the angle onto my tablesaw and set for a 1/2" cut.
The kerf of the blade is 1/8" and my blades are 1/8" thick.
I then ripped 3 lines into the walnut.
I put the blades into the 3 lines. (very snug fit)
I turn my sharpening stone upside down and run it across all three blades at once.
It works well. And since I'm doing all three blades at once, I don't have to count the number of passes I make.
 
#11 ·
Doug, the PM method will put an edge on the blades, but I prefer to take them out and sharpen them on the blade grinder. It will even the blade heights out, if you're off a hair, but it's easy to take them too far, then you'll have to go in and reset them anyway.
Cmaeda, did you get your board edged properly?
 
C
#12 ·
Yes, I did test out the jointer after sharpening it and it performed really well. There were no dips, grooves or sniping on my test board.
I forgot to add that I did swipe each one 3 times on a 600 grit diamond stone after I took each blade out of the jig.
I also coated the jig with shellac afterwards to help minimize wood movement. I don't think this will affect the performance of the jig. I just coat all my jigs with shellac if they are made of solid wood and if I think I'll use it more in the future.
 
#13 ·
Some great ideas here, guys. I've just run into a dull knives situation with my jointer, and going back and forth trying to decide whether to replace or sharpen. I did order a spare set of knives, and I've got an email out to my sharpener to see what they'd charge me, but I like cmaeda's idea and jig. May try that.
 
#16 ·
FYI,

Hendrik Varju from "Passion For Wood" has recently had an article published in Fine Woodworking magazine on sharpening jointer knives while still in the machine. Jan/Feb - 2012 issue, as well as an article on their website from 2011 on building a jig to sharpen planer knives while still in the machine.

Gator
 
#17 ·
Fine Woodworking describes a nice method of sharpening your jointer knives in place. You make a small wooden block that locks your cutterhead in the correct position. Then you lower one table out of the way to sharpen the blades. It works well.
 
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