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Thread: Sharpening Jointer Knives.

  1. #1
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    Sharpening Jointer Knives.

    Spent some time getting my pm 54 6" jointer back in shape.

    Pulled out the blades and decided to give sharpening them a shot.

    So I measured the angle on the blades, and I'll be darned if they weren't 45 degrees. So I cut a little block of wood at 45 and used that as a guide to hone up the blades on my diamond stone until I could shave hairs with it. Did that to all three blades. Then the fun started.

    Forgot to mark the TDC before I started sharpening, so put one bladed back in, guessed at TDC and used that as a mark to do the rest of them. Used one of those magnet jigs to set the blades. Then I used a magnetic dial indicator to check it all and set the outfeed table to just slightly (.001 ?) higher than the blades. Does that sound right?

    Did some test planing and it seemed to work pretty darn well. Much easier to push the wood through the planer, and it had a much 'smoother' sound than the old dull blades...

    Only took a few hours, but I should be back in business...
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
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  2. #2
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    A thou high isn't a bad starting point for the outfeed... to be twiddled with depending on how you use the jointer & what your results are. The slower (without ever stopping) you feed stock through, the nearer the outfeed can be to level with the highest knife. Too high & your workpiece will have a funny "tip up" near the leading end, too low & it'll go concave on you, and also have one snipe near the trailing end. If your one-thou spot is giving you good results, then it's right for how you use the jointer.

    Sure sounds "softer" with nice sharp knives in it, doesn't it?

    I use the "lift and drag" method to set my knives - it's reliable & quick.
    -- Tim --

  3. #3
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    To set my jointer knives I use the plexiglass magnet method. I seplexiglass on the outfeed table overlapping the knife. Pit a magnet over the knife tighten the blade and go on th the next one. I usualy start about 1/2 thou proud on the outfeed.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  4. #4
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    That sound great Brent. It is always refreshing to use a tool right after a tune up. Brings back that "new tool smell" . When I changed knives for my dad recently, I used Don's method except I used glass plate instead of plastic as that was what was handy. Very quick and reliable.
    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C. Clarke

  5. #5
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    Thanks guys!

    The plexy and plate method sounds very similar to the little magnetic jig I've got. It's basically 2 bars and 6 magnets. 4 magnets keep it flat on the outfeed and two of them bring the blade up to height.


    Quote Originally Posted by Tim Hofstetter View Post
    Sure sounds "softer" with nice sharp knives in it, doesn't it?
    It does have a much softer sound. Before when I would turn it on, without even running wood through it, it would sound like it was ripping the air. Now it's much more of a 'whirrrr'...
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


  6. #6
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    Did a little more searching. This article here describes pretty much what I did, using the same tool I used.

    Jointer Knife Change Tutorial

    I suppose if I sharpened or adjusted my jointer knives more than once every couple of years I'd get his down!

    The only difference between what I did and the article is that before I adjusted my knife, height, I put my jack screws all the way to the bottom, and then after I had the knife height set, I snugged them up to the knives for support.
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


  7. #7
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    I can't add anything to setting up the knives, but I can add a cool jig that a guy named "Dizzy" shared (he has passed away since).

    Dizzy's jointer/planer knife honing jig

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    Shown here are planer knives, but you can understand that jointer knives can also be done with a similar jig.
    Last edited by Stuart Ablett; 11-01-2009 at 05:31 PM.
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  8. #8
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    Now thats a slick sharpening jig.

    If I can just figure out how to make it work for 3 blades, that would be killer.

    I guess I could just order a new set of jointer knives. Once I get both sets worn down, I could then go and sharpen all 6 blades and then have 2 sets of sharp knives!
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


  9. #9
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    Quote Originally Posted by Brent Dowell View Post
    Now thats a slick sharpening jig.

    If I can just figure out how to make it work for 3 blades, that would be killer.

    I guess I could just order a new set of jointer knives. Once I get both sets worn down, I could then go and sharpen all 6 blades and then have 2 sets of sharp knives!
    Makin' it work for 3 knives ain't too hard... you mount all three on the same side, same orientation, like sheets of plywood leaning against a wall. On the other side you attach a brass rub strip (wears better than wood), which can be vertical or angled, it doesn't much matter. The brass rub strip should be slotted so it's got a little adjustment to it.

    The only trick will be in getting the three knives lined up - if they're "holed", the holes won't be quite in alignment with each other so ya'd hafta' use an undersized screw to pass through all three holes. If they're not, it's easier... one clamp'll hole 'em all.

    They'd all register against three little curbs in the body of the jig, all cut with the same height setting but stepped over 3/32" (for 1/8" knives) per pass to make the curbs exactly the same. Go a little further & add two setscrews to each curb for fine adjustment (in case the knives aren't perfectly identical).

    EDIT: The classic way to do it, though, is to work two knives at a time till they're about half done, swap one out for the unworked knife, work 'em till the first is done & the last is half-done, then swap out the done one for the first one you took out - at which point you'll have two half-done knives again so you can finish the job.
    -- Tim --

  10. #10
    My thinking about the honing angle is that it's less important than the height above the cutterhead. If the knife edges are close to the cutterhead it will limit the depth of cut, and if they're too high above they won't have enough support. Trial and error imo. I don't like to take heavy cuts on the jointer so I opt for support. The angle is important though...too small an angle and the edge is weakened, too large an angle and it hammers the chips off...but it's a range. Personally I tend toward a smaller angle since I think it makes a smoother cut, and I have a good setup for sharpening as it's needed.

    The outfeed table ideally will be exactly even with the knives at TDC. This is difficult to achieve...I agree with Tim that a thousandths is acceptable. The infeed table is lowered to determine the depth of cut, and as the chips are cut off, the piece slides right onto the outfeed table with full support and no snipe on either end. Just as important is getting all 3 knives even with the outfeed table, since the highest one will be doing all the cutting. This is also difficult to achieve to perfection. Even a jig like the Jointer Pal may not keep the knives from shifting slightly as the gib bolts are tightened...rig up a dial indicator to check this...I think you will be surprised. Anyway, some deviation has to be acceptable or you will end up in the nut house.

    As an aside, I bought this jig from Lee Valley a few years ago:
    http://www.leevalley.com/wood/page.a...=1,43072,43078
    and never really used it...maybe a couple of times. My jointer now is a 12", and of course the jig does me no good for that. 20 bucks plus shipping and you can have it. I'll email you a pic if you want. Let me know.

    Cheers.

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