Fret Sawn dovetail waste removal results in excessive tear out

  • Creator
    Topic
  • #425197
    Kevin Farris
    Participant

    I am not opposed to methodically chopping waste from my dovetails as they come out as clean as I can make them and I am quite pleased with the result.
    I have been playing around with fret sawing out the waste (to move things along a little faster). I am currently leaving about 3/32-1/8″ of material to be chiseled out.
    I have tried in maple, ash, oak, and poplar, and each time I experience excessive “childs tooth” socket tear out. I am using very sharp chisels (25 degree) and trying to nibble off small amounts, but by the time I get to the shoulder the breakout has already started.
    Is there a technique to avoid this or is this method prone to more tear out? Even though nobody will see it, I do not like knowing it is there.

Viewing 11 replies - 1 through 11 (of 11 total)
  • Author
    Replies
  • #425215
    Clifford
    Participant

    @narrs

    I have experienced the same thing and look forward to any insight! I also include black walnut and alder in the list.

    #425230
    Edmund
    Participant

    @etmo

    This makes no sense to me — maybe I don’t understand what is being said.

    The OP is sawing out waste from a dovetail, leaving an 1/8″ or so to be chiseled out. Then, during the chiseling process, somehow tearing out occurs (here I thought tear-out was a planing issue, didn’t even know it was possible with a chisel), and yet the OP is claiming the saw is to blame?

    How does the last 1/8″ know if all the previous waste was removed by a chisel or a saw? …especially since a saw is just a bunch of small chisels cut from a larger plate of steel…I have to hear this explanation.

    #425405
    SmokyRick Crawford
    Participant

    @smokyrick

    Are you cutting from every edge toward the middle? If not, this may help. This is all that I can think of from what you describe.

    In the middle of Northern Illinois, USA

    #425458
    mictau
    Participant

    @mictau

    Hey Kevin,

    I’m not sure there is a great solution to this. I think the normal approach of shooting for the sky while paring is problematic in this case. The extra torque created as you hit the top of the unsupported fibers increases the likelihood you will rip out the end fibers making it really hard to get a clean cut started.

    The only time I’ve had much success with this is if the dovetail is large enough that I can come in from the top, bevel down, and then working parallel to the width, slowly bring it down until I have enough room to make a clean paring cut at the base of the fibers. Once I have a start I’d pair like normal. Although I make a lot of smaller pieces so this often is not an option.

    Another thought, although I’ve never actually tried it, might be to use a needle file to take the waste down closer to a 16th or 32nd before you start paring. It seems like if you bring it down enough you could significantly reduce the issue with the unsupported fibers.

    Mike

    #425498
    Kevin Farris
    Participant

    @mossy-cup

    After sawing the bulk waste parallel to the knife line, I have been using the bevel away from the knife line on side A of the board, essentially paring the waste to the knife wall about half way down the wall. This works normally, as if I had chopped out the waste.

    When I flip over to side B of the board, the left over waste (now unsupported) is where the difficulty arises.

    I start paring/shooting small increments of waste (bevel away), and by the time I get to the knife line the torque has already started the breakage below. The resulting shoulder is still clean, crisp, and undamaged. It is about 1/16″-3/32″ below the shoulder where the breakage occurs the remaining way to the half way point where I would meet the side A stopping point.

    Smoky Rick, I may try to do what you describe with a narrower chisel. Shoot to the sky, but at an angle from the edge of the waste.
    I am located in Belvidere, also in the tundra we call the middle of Northern Illinois. Quite enjoyable weather lately, Brrrrrrrrrrrrr.

    It just came to me that I could probably shoot the to the sky with the saw on both sides and get closer to the shoulder, leaving a more controllable hump in the middle. Maybe I need to work on my fret sawing instead.

    #425574
    deanbecker
    Participant

    @deanbecker

    Are you creaping up on the shoulder or cutting the whole 1/8.
    I cut close to the shoulder and pare the last out with a circular motion using the corner of a really sharp chisel.
    If i leave too much i cut 1/64 th or less at a time back to the shoulder.
    Just pare off the edge every time. If the wood does t curl off the edge of the chisel it is dull.

    #425705
    David Perrott
    Participant

    @dperrott

    Does this not happen when you chisel all of the waste out? Normally I think this is a “sharpness” issue.

    #425745
    Harvey Kimsey
    Participant

    @hkimsey

    What sort of fret saw blade are you using? Are you sure it isn’t a coping saw. Some coping saw blades are quite coarse and aggressive. I recently got a KNEW Concepts fret saw and the finer teeth that were on that saw did an amazingly better job than any coping saw blade. Look for pegas fret saw blades.

    #426179
    SmokyRick Crawford
    Participant

    @smokyrick

    @mossy-cup I am over near Rochelle. From what has been said, I am wondering if you have got the idea of paring correct. To pare the wood down should be a small movement at a time with the hands both on the chisel. Slightly moving the chisel to slice the wood away from the area needed. I guess slice is the key word. While you are talking about “shooting to the sky” I am thinking of someone starting to remove the bulk of the waste, rather than paring the last little bit out. Paring should involve some sideways movement of the chisel which facilitates with the slicing action.

    In the middle of Northern Illinois, USA

    #426259
    Kevin Farris
    Participant

    @mossy-cup

    Thank you everyone, I have been creeping up to the shoulder in the past but using impacts to the chisel.
    I have recently tried more arduous paring without any impacts to the chisel and it does work better, just extremely tedious if too much material is left.
    The fret saw I’ve used is the Rob Cosman offering, I do have a Knew Concepts Coping saw and love it.
    I may invest in the Knew Concepts Fret saw as well, it would be nice to have more depth capability.

    #433835
    David B
    Participant

    @dbockel2

    There are 2 parts to chopping a dovetail with a chisel. It’s not just chopping, but also the methodical levering out of the small layers of waste (levering out waste is an upward force while chopping is a downward force–and in my experience, the levering process actually removes more wasted than the chopping part). It is one thing to clean up a joint by paring it with a chisel to refine it to the knife wall, but quite another to chop. If you simply tried to chop off the front 1/8″ of a board with a chisel, I bet OP would run into the same issues. This sounds like an “improper” technique that was probably conceived as a good idea but in reality is a combination of 2 sloppy techniques.

    Fwiw, I have dovetail tearout issues from chopping softwoods because of the nature of softwood vs. hardwood, but it is not because of the process that OP is describing. And yes, smaller chisels can improve the tearout issue because less material is taken out with each pass. Just make sure to stay true to the knife wall or else the joint won’t be perfectly straight.

Viewing 11 replies - 1 through 11 (of 11 total)

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