Thursday, July 16, 2015

1 way tapered sashisen


You got me. I spend the nights looking japanese instagram: http://pinsta.me/kai46satsuki

Sometimes I do find useful stuff, like this 1 way tapered wedge. I really don't see the point for the second taper since you don't want to push on the direction of the long sides of the sashisen, only on the short ones, which are the ones directed along the centre line. What's more, I would do the sashisen slightly loose in that direction with the wood movement aligned along that line so the movement won't affect the fit of it.

Maybe some diagrams help.

Case a): 1 taper only, the wedge is not touching the long sides of the mortice. The forces will follow the red arrows.
 If you have a 2 taper, the force will act in different directions and you would be actually pulling less the joint than in the first case. Furthermore, you also tend to separate the pieces from the centre line. This is the case b)
Looking at the diagrams, it's clear that what I want to achieve with the sashisen is a) and not b).
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7 comments:

  1. JasonJuly 16, 2015 at 10:56 PM

    I agree completely. Shachi-sen tapered two ways seems wrong. I think that what Chris Hall was referring to, when he said that shachi-sen are tapered two directions....I bet that he means that the shachi-sen itself is tapered, and also the mortice as well. That adds up to a double taper in my book (kind of). I should buy his book. Really. I need all the help that I can get, and I greatly admire his skill as a joiner.

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    1. JasonJuly 16, 2015 at 10:57 PM

      That's a beautiful joint, BTW!

      Nice!

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    2. Sebastian GonzalezJuly 16, 2015 at 11:20 PM

      double taper joint... that makes perfect sense.

      I like this kind of little mysteries, if you knew the answer no need to ask why, but since we don't know, we need to find out. Then is when I find I really learn something.

      Delete
  2. JasonJuly 16, 2015 at 11:27 PM

    Assuming that we are correct in our thinking, Chris left all of the clues, right there in his posts. We needed to gain some experience, then actually do the work, for the hints to make sense. The perfect lesson, but frustrating for someone like me who wants the information NOW!

    Please allow me to thank you once again for implementing this joinery practice. I have learned more in the last few weeks than.....I don't know, really! My muscles are learning! This is a great thing!

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    Replies
    1. Sebastian GonzalezJuly 17, 2015 at 8:50 AM

      nah, nothing to thanks, I just said the "let's do it", the mood was in the air. If I were alone, this would have stopped after the first failure. Thanks you guys for keeping the bar up. I'm looking forward to the next round already.

      Delete
    2. Sebastian GonzalezJuly 17, 2015 at 5:17 PM

      and why nobody told me I wrote it wrong, it's shachisen, not sashisen. My dislexia is really worrying.

      Delete
  3. Gabe D.July 17, 2015 at 7:16 PM

    Romanji is anybody's interpretation. When we start to get really hard-core we'll just use the katagana/kanji to avoid confusion.

    And you should be thanked Sebastian, right place, right time, but you actually DID it to get us all started. I definitely second than we'll probably end up getting Chris Halls books. These exercises will be taking us right along to non-orthogonal joinery like a splay legged saw horse.

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