Proper use of marking knife

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  • #141054
    rjmarshall17
    Participant

    Hi,

    I recently watched the video, and actually made, on Paul’s shooting board. One problem that I had was that the dados for the 45 degree wedge in particular ended up too wide. I think that the problem was caused by trying to over compensate for my marking knife cutting into the wedges when trying to mark the dados. So my question is: How do I hold the knife in order to run it along the edge of a piece of wood to use it to mark the walls of the dado without cutting into the piece of wood?

    I’m not sure I’m making any sense, but I hope someone will know what I’m saying.

    Thanks,

    Rob

    #141057
    J. T. Senghas
    Participant

    Rob, I’m a newcomer to this forum, but I’ve watched that video and am familiar with the techniques, so perhaps I can be of some assistance.

    Before discussing knife techniques I want to emphasize that your problem may just as well have been caused by compressing that “knifewall” outwards while chiseling, depending on your technique. Note that Paul always either cuts and flicks a chip out of the way or starts a millimeter or two from the knifewall before chiseling firmly to avoid having the bevel drive that surface outward.

    As for knife technique, it is most important to avoid allowing the blade to turn into the edge of the board being used as a straight edge and to make sure the first pass is VERY light. You just want the bevel of the blade to follow the plane of the straightedge. This requires the blade to be tipped at about the angle of its bevel but not for the handle to be twisted above the edge of the straightedge, which would tend to cut a chip from that board. START LIGHTLY!

    #141058
    kevinjames
    Participant

    I’ve heard Paul say several times that he is, in a way, trying to reach slightly under the piece he is marking. If the dado comes out slightly undersized, a pass or two with the plane makes it fit. Hope that helps.

    Kevin

    #141081
    Ed
    Participant

    If this were a simple housing square to the edge, you would knife one side, cut down with your chisel, place the board that is being fitted against that cut and then just mark the location of the second edge with a prick of your knife. You wouldn’t trace along the board. Instead, you’d use the square, registered against the prick. Since it is just a prick, you have a lot of control, e.g., you can reach a little under the piece being marked if experience shows that otherwise things come out loose and you can make sure to use the knife so that the wall lands on the prick and the sloped part of the cut, what Paul calls the bruising, lands in the waste.

    The shooting board is a bit trickier since one edge of the wedge is at 45 or 90 and the other is at some arbitrary angle. One approach is to mark both with a pencil, then use a steel rule to knife the line that is at an arbitrary angle (the one that is neither 45 nor 90). Cut that down, place the wedge against the cut, and make a prick with the knife. The second wall will be at exactly 45 or 90, so you can bring the square in now to mark the second side, no need to trace along a wooden batten. Now cut the housing and test the wedge. It is impossible to be loose with a wedge, really, because you will slide the wedge until it is tight, mark the end that overhangs the chute, and then cut to length. You can, however, have the wrong angle for the housing vs. the wedge, but you ought to be really close. A couple light passes of the plane along the wedge will get the angles to match. (Do that before cutting to length).

    #141094
    rjmarshall17
    Participant

    Hi,

    I think the idea of making marks with the knife at both ends of the board and then using a straightedge, holding the knife in the mark to ensure that the straightedge is lined up correctly (probably need to check it a couple of times to make sure it doesn’t slip), sounds like the best approach.

    Thanks for all the help,

    Rob

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