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  1. #16
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    They look like the real thing, Fuzzie. No excuses now - perfect half-lapped dovetails every time from now on.....

    Cheers,
    IW

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  3. #17
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    Default And a fishtail

    With the remaining slot cutout it seemed like a reasonable idea to attempt a fishtail...

    fishtail1.jpgfishtail2.jpg

    Shaping this one was a bit more challenging. In the end I found it easiest to nibble at the edges by making shallow relief cuts in from the edges using a 1mm stainless steel cutting disc in the angle grinder, then moving to the wheel grinder to smooth out the curve.

    The slots were cut from the blade blanks before surface grinding so there was a fair bit of work involved in lapping out the rough manufacturing surface to get to a clean face. While I was going through the process I noticed a few unexpected spots of blood popping up here and there. It turns out the square edges got so sharp they were slicing my fingers while holding the blade to the stones. The sharpened bevel edge should be pretty impressive. On the plus side I'll probably only ever have to sharpen it once or twice in it's lifetime.

  4. #18
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    BTW. Looking at the Blue Spruce and Lie Nielsen fishtails, I suspect this one won't actually be flared enough to do the full job.

  5. #19
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    It looks ok to me Fuzz (as far as I can tell from a pic). You might have to ease them back a bit more if you want it to get into the corner of the socket with the cutting edge parallel to the back of the socket. I just checked some Trig tables and if you stay within the 'standard' dovetail ratios of about 1/6 to about 1/9, the corner angles of the corresponding sockets are (roughly) between 8o & 85 degrees. So a ruler put against the points & touching the sides about 25mmm back from the edge has to make an angle of at least 80 degrees. I did the calculations out of interest, I'm not that fussy! I was just curious as to what minimum angle was needed, because the less acute it is, the more robust the points are going to be. In reality, I'd do what you will almost certainly do - try the chisel out in a few sockets & it it don't fit right, grind a bit more off!

    One comment on your design I will make: I'd lose those bevel edges along the upper part of the blade right smartly, if they are sharp enough to cut your pinkies! You shouldn't need them, even at the business end, though they do give you more aggressive points to cut into the corners with. Not much fun working with your fingers wrapped up with bandaids.....

    Cheers,
    IW

  6. #20
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    Hi Ian,

    The main edges doing the (finger) damage are the right angle between face and verticals on the sides. The arrises at the bevel on top aren't really a problem as the included angle is much greater (135 ish).

    I've happened on this problem before after flattening the face of other normal chisels. After getting the face nice and flat and polished then the arisses are always sharp to. Do experienced people as a matter of course break the edges all around when preparing chisels?

    The bevels on this chisel are not there specifically by design, they basically appeared due to the angle of presentation to the 6" grinding wheel and flipping the blank over while grinding the sides. Trying to intentionally bevel those curved sides would be a challenge.

    I've since thought that the fishtail wouldn't really work much different to a 'dovetail' chisel diminished completely at the sides to knife edges (edit- actually scrap that statement, I was thinking about pins not sockets there, the rest follows though) , but that really would introduce a cut danger zone. The skew on the other hand will let you manoeuver into a deep corner or edge and make a slicing cut as when skewing a plane when you hit tough grain.

    When I get around to trying both, I guess I will know.

  7. #21
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    Quote Originally Posted by Fuzzie View Post
    ....Do experienced people as a matter of course break the edges all around when preparing chisels?....
    Until a few years ago, I hadn't noticed a problem, having mostly older, (very) used chisels, well-duffed and marked up with use. But when I bought a set of LN socket bevels a while back, I had a quick lesson on the effects of super-sharp corners, alright - they were lethal! I certainly 'fixed' those pretty quick. I went at them with one of those inexpensive diamond paddles & slightly rounded the edges - it only took a few passes and you can't really see any difference with the naked eye, but they had lost the ability to cut me so easily. I didn't touch the last 25mm back from the cutting edge, so the corners of the blade remain sharp (nothing I detest more than duffed corners!). There's been a bit less blood on my work since then....

    Cheers,
    IW

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