Knife wall problems

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  • #314000
    CJ
    Participant

    I’m having problems with transferring my knife wall lines around the perimeter of the side and end components when laying out my dovetails. My pieces of prepared stock(sides and ends are square). I’ll end up 1/64th of an inch off at times where the beginning knife wall point meets the end point. I’ve watched Paul, and he says to imagine trying to get the knife point under the blade of square. I’m using the Stanley knife he suggested. Any suggestions as to what I’m doing wrong? I’ve checked my both of my squares against each other and they are true. Both quality Starrett squares. Thanks

    #314002
    Edmund
    Participant

    You say your components are square, but if you’re transferring your lines around correctly, it means they are not square. It’s easy to believe your Starretts are square, but everything else needs to be scrutinized.

    Also, and maybe most importantly, I’m not sure I have heard Paul say to get your knife point under the square, but I have heard him say “almost as if your knife is going under the blade of the square” — it’s a fine distinction, but so is a 64th of an inch…if you go under the blade, how far under do you go? How do you go the same distance under the blade each time?

    I may be wrong, but it seems to me the point of Paul saying that is to get you as close to the edge of the blade of the square as possible, so your markings will be as accurate as possible. The edge of the blade of the square is the line you wish the transfer onto your wood. If you go somewhere under the blade, you’re now essentially free-handing your knife line, just using the edge of the blade of the square to stabilize your free-handing. Since your posture might be different, your angle of approach to the blade might be different, your grip on the marking knife might be different, etc, etc, the distance you go under the blade might thus be different, and you’ll be unable to trust the accuracy of the knife line you just made…I hope I’m explaining that clearly, and I apologize if not.

    Can you post a video of yourself transferring a knife nick around a squared component? Maybe someone will spot some error in your technique.

    #314007
    Darren
    Participant

    To add to the good points above, make sure you use the same reference face as much as you can. By that I mean: from one edge knick, mark both adjacent sides. Then from of those marks do another face, then all the way back to the first mark as a guide to mark the last face.

    If you just go face-to-face-to-face any errors you have will be magnified by the time you get all the way around.

    Darren.

    #314008
    CJ
    Participant

    Thanks for your replies. This is all very helpful. The idea of nicking the edges from the reference face makes sense, rather than going face-to-face-to-face as I was doing.

    #314010
    Ed
    Participant

    Another way to think about @tenjin ‘s comment: You should have one reference face and one reference edge. Those are the only surfaces the handle of your square should touch. You have four lines to draw, but only two surfaces will be used to set the square.

    Do things get better if you just make the lightest possible marking? Try making one gentle cut that just barely marks the wood. This isn’t useful for real work, but if it is better, it suggests you are not controlling the force of your cuts and are moving the square with the knife. One version of this is to start the cut with the knife leaning to the side (as you must with this kind of knife), but then twisting the knife handle as you pull the line so that the knife is perpendicular at the end, which will move the square.

    Another error is to put the knife into the nick vertically when transferring around a corner, pulling the square up to the vertical knife, but then angling the knife when you pull the line, or vice versa. This would give you about 1/64th error.

    #314023
    Richard Hopper
    Participant

    One other thing; put the knife blade into the mark and move the square to the knife. Other than that, I echo the other comments about face side and face edge being the only sides your square should reference from.

    #314026
    David B
    Participant

    What Tenjin said. I’ve seen Paul not use the same reference point in some of his videos, but he has clearly said it is because he has carefully milled his stock and knows it to be perfectly square. Perfectly square to him is PERFECTLY square–maybe a harder level for some of us mortals to attain. But still, making sure you are using the correct reference point (and knowing when to flip that square/stock over as you rotate your stock so that you continue to correctly use the same reference face) is critical.

    #553415
    David Alvarez
    Participant

    I’ve been struggling with this as well, but I have noticed, particularly in Paul’s Dovetail Caddy series where the camera operator zooms in super close to him cutting various knife walls, that he holds the knife at an slight vertical angle to the edge of the blade of the square. My guess is that its a 15 degree angle, which would match the angle the knife was ground at, totaling a dead vertical cut. Paying attention to this on top of all the other points people have been making should go a long way towards addressing both of our struggles.
    The sketch below (from Mr. Seller’s blog, entitled “What is a Knifewall?”, https://paulsellers.com/2017/12/whats-knifewall/) ought to clear things up a bit.

    #553452
    GfB
    Participant

    I concur. I was having the same troubles, except I was using cheaper big box store squares. I did four things at once;
    1. began using Starrett
    2. made sure I was tilting my knife into the waste side
    3. using a reference face/edge
    4. lightly marking first

    I don’t know which were originally in error, but I am now finding much better measurements.

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