Another (sort of) Japanese Toolbox


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Finished another (sort of) Japanese toolbox. Much like my last one, this is a wedged tenons for the sides and a float panel in the bottom, instead of nailed in. Maple, with scraps of jatoba and black walnut for the accents.

 

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What's it going to hold? Training knives.

 

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The top one is black locust and black walnut, the middle is katalox, and the bottom is cherry (from a tree limb that fell in my yard some time ago).

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Tenons are traditionally wedged 90 degrees to the grain.  If you wedge with the grain as is shown in the pictures, there can be problems with splitting the sides of the box.

 

Wedging the tenons vertically may have been a better engineering choice.

 

I just wondered if you had considered this, decided against it, or just lucked out in not having it split.

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I've wedged a lot of tenons and not had them split, except for the one time I over-drove a wedge on another project. I'm just careful to not make the wedge too long, too thick, and always drill a relief hole at the end of the saw kerf.

 

Rotating the wedge 90° would be worse, because I'd then be pressing with the long grain of the mortice sides, and could easily break off the wood around the mortice, and fact that then I really would be wedging along the flatsawn grain of the tenon.

 

Anyway,I'll be honest - I've never seen what you described illustrated anywhere - including my book on Japanese joinery, where wedged tenons are frequently use. I'm not saying it's not done, but I have my doubts about it being particularly traditional to only wedge 90° to the grain.

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Wow, I thought wedging 90 degrees to the grain was common knowledge.  It is mentioned in just about every book/article on wedging Windsor chairs.  In the Paul Sellers' link he mentions that one of his workpieces was nailed above his workstation by his boss as a reminder for getting it wrong.

 

It would be interesting to see some destructive testing on how much of a difference it makes.

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Indeed the tendency is to orient the wedge 90 to the tenon...it just seems right. The grain of many tenons is naturally oriented 90 to the grain of the mortice board which is why we think the wedge must be oriented to the tenon, but when the grain is parallel we discover the error of our orientation because it appears cattywampus.

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Ok, I think there's some confusion here.

 

The piece that is wedged (the tenon) is flatsawn. Thus the wedge is driven through the endgrain, 90 degrees to the flatsawn grain. It's the same as shown in image 8 in http://www.woodworkersinstitute.com/page.asp?p=449 or the 4th image at http://paulsellers.com/2014/02/hard-days-work-home-work/ or the 3rd image at http://pegsandtails.wordpress.com/2010/05/26/making-an-english-comb-back-windsor-chair-part-three/

 

I thought you were describing something else entirely.

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That Paul Sellers picture is an example of what not to do!  Did you read the text?  It was an example of fail sauce.

 

The orientation of the wedge in the tenon shouldn't matter (look at ax handles sometime, they get wedged every which way).  The mortised piece is what typically dictates the orientation of the wedge.

 

Let's go Roy Underhill for a moment.  Your side piece is a log, your wedge is a glut...which way do you orient the glut to cause the log to split?  Answer:  Exactly as you did in your box.

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First, ok - now that we're all on the same page regarding what exactly we're talking about (wedge direction relative to the board with the mortise, and splitting the board with the mortice - seriously, I was incredibly confused)... I understand and agree - to a point.

 

 

Here's my logic (read a post or two up)... the weakest part of wood is related to shearing along the grain, yes? That's how wood splitting works, whether you're starting from end grain or somewhere in the middle. That's why splitting wood with a wedge in the end grain can be more efficient than cutting, or why you brace from below (using compression).

 

So, as I built the box, I have two choices - add additional pressure to the top/bottom of my box sides, which have quite a bit of wood to work with, or I apply additional pressure to the end grain of my boxes, which don't have that much extra "meat" behind them, potentially splitting off the outside edge of the through mortise. Like a wedge in end grain.

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By wedging with the grain on the panel you have created a new "internal" stress that can create a fracture, a.k.a. a check. The tenon is supported by the mortise so there's no problem with whatever direction you choose to wedge it. Provided you don't over size the wedge. I think there is plenty of material to the outside of the mortise to support a wedge over time...woodworkers do that all the time.

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  • 4 weeks later...

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