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Thread: This is a jig I just built

  1. #1
    Join Date
    Mar 2006
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    West Sacramento, CA
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    7,359

    Default This is a jig I just built

    for grinding a bevel on a set of six-inch carbide jointer knives.

    I inherited this Craftsman six-inch jointer some time ago, intending to sell it for the PO, and after tuning it up to sell it, decided to make use of it for our some of our front porch overhaul. This jig is built from stuff on hand, a length of three-eighths by one-eighth steel and some bits of half inch copper tube.



    The holder is a big spring, with slanted slots in each turned-in end. The angle of slots gets the bevel face at the approximate angle to lie almost flat against the face of the spinning grinding wheel.

    The cross bar is also slotted and fits over the sprung part. The length of the distance between the slots on the cross bar allow the spring tension to remain holding the blade securely. The bottom of the cross bar rests in the guide slot ground into the top of the tool rest addition. The copper pieces fit into slots and hold the cross bar to the spring part.



    I copied the angle of the original bevel. The knives would still be fine but for a nick near one end. So that means grinding a new bevel on all three blades to remove the nearly sixteenth of an inch deep nick.





    It purred through taking a sixteenth off the edge of a scrap of one-inch shelf pine, leaving nothing but smooth and flat. The old hunk of doug-fir two by six, an actual scrap of old deck or step plank from the porch, with house paint on one side, got clean and smooth in a couple of noisy passes.



    Now the new sharp edges are a bit dull. I may have to adjust the bevel angle, and do a final hone with a stone. A stone hone.

    Speak softly and carry a mouthful of marbles.

  2. #2
    Join Date
    Mar 2009
    Location
    Texas
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    5,410

    Default Re: This is a jig I just built

    Nice.

  3. #3
    Join Date
    Apr 2009
    Location
    Mountain lakes of Vermont
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    14,759

    Default Re: This is a jig I just built

    Very clever! I'm impressed.
    I was born on a wooden boat that I built myself.

  4. #4
    Join Date
    Jan 2009
    Location
    se pa (Bristol PA)
    Posts
    4,583

    Default

    Nicely done but those blades are really cheap to buy
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  5. #5
    Join Date
    Jun 2003
    Location
    Central Coast, Ca
    Posts
    28,964

    Default Re: This is a jig I just built

    Diamond for carbide

  6. #6
    Join Date
    Jun 2010
    Location
    Between Bourgeoisie and Proletariat - Australia
    Posts
    5,299

    Default Re: This is a jig I just built

    The cross piece is your guide?

    I'd like a way of grinding my thickness planer blades. I too have a nick from an undetected screw/nail in some recycled wood.
    They're not overly expensive to replace, but expensive enough that a convenient sharpening jig would be used (and also, reduce and reuse).

    Nice work.
    It's all fun and games until Darth Vader comes.

  7. #7
    Join Date
    Nov 2008
    Posts
    34,720

    Default Re: This is a jig I just built

    Quote Originally Posted by Jim Mahan View Post
    for grinding a bevel on a set of six-inch carbide jointer knives.

    I inherited this Craftsman six-inch jointer some time ago, intending to sell it for the PO, and after tuning it up to sell it, decided to make use of it for our some of our front porch overhaul. This jig is built from stuff on hand, a length of three-eighths by one-eighth steel and some bits of half inch copper tube.





    I copied the angle of the original bevel. The knives would still be fine but for a nick near one end. So that means grinding a new bevel on all three blades to remove the nearly sixteenth of an inch deep nick.

    .
    Quote Originally Posted by DeniseO30 View Post
    Nicely done but those blades are really cheap to buy
    Or professionally sharpened, but Jim just didn't want to leave the farm.



    Quote Originally Posted by gypsie View Post
    The cross piece is your guide?

    I'd like a way of grinding my thickness planer blades. I too have a nick from an undetected screw/nail in some recycled wood.
    They're not overly expensive to replace, but expensive enough that a convenient sharpening jig would be used (and also, reduce and reuse).

    Nice work.
    I gotta say 'Nice work' too, Jim.

    If you're not a big user of the rabbetting feature on a jointer, you can offset the knives enough that the little ridge on the workpiece disappears.

    If that ridge is present, it means that it lifts the workpiece out of the cutterhead such that it very quickly begins to behave as if the knives are set too low . . . Which they are, effectively, on just that nick.

    On a thickness planer, such a nick disfigures the work, but doesn't distort the lumber.

    Much easier to demonstrate than to explain!

  8. #8
    Join Date
    Sep 2002
    Location
    On the river, Auckland, New Zealand
    Posts
    6,256

    Default Re: This is a jig I just built

    Quote Originally Posted by gypsie View Post
    The cross piece is your guide?

    I'd like a way of grinding my thickness planer blades. I too have a nick from an undetected screw/nail in some recycled wood.
    They're not overly expensive to replace, but expensive enough that a convenient sharpening jig would be used (and also, reduce and reuse).

    Nice work.
    If its just a slight nick, try moving one of the knives sideways 3 or 4mm and reset, check that it doesn't clip anything when you rotate it by hand and you're good to go. When the nicks dont coincide you'll get a much better finish.

    John Welsford
    An expert is but a beginner with experience.

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