Craftsmanship in Wood

I'd probably cut in the pins at this point and save the fine tuning for afterward. I found in my recent build that I was hunting for a fit that found its own way once the joint was seated with the pins. If I kept going I would have possibly taken it out of square from too much fiddling. It was exactly square and tight when seated but appeared to need more work before hand.

Yes, 4-way mitered connections are a tricky matter and it can feel a lot like you are chasing your tail at times. As you do them more and more, they seem to get easier.

Chris, that's true but as this is my second attempt at such a joint, I was expecting mastery by this stage...

I'd probably cut in the pins at this point and save the fine tuning for afterward. I found in my recent build that I was hunting for a fit that found its own way once the joint was seated with the pins. If I kept going I would have possibly taken it out of square from too much fiddling. It was exactly square and tight when seated but appeared to need more work before hand.

That's what I ended up doing Brian. It was time to move on. It was also possible that fidling around with the four way mitre was procrastination with regard to trying the pinned joint for the first time.

I started with the trenches on the Tenons first: And then the trenches in the morticed Keta piece: Finally I lightly inserted some pins: The pins in the picture are actually slightly undersized and have no taper. I have some slightly larger stock which I will use to properly fit to the joint. That will have to wait to tomorrow.

I hope I made mention in the mailing to make the shachi-sen with a bulbous/hook-shaped/barbed head to facilitate their removal.

Chris, you did. My intention was to simply leave the sen over length, thus providing the necessary purchase to remove them. I only plan to drive them in finger tight. This has allowed me to fabricate them fairly quickly using the table saw, and focus on fitting the joint. I am cognisant of the fact that, historically, I make slow progress on these projects and I'm making a dedicated effort to keep things moving, for everyone's sake.

I didn't get around to final fitting today however I did manage to finish squaring up the stock for the hip rafter. Only a couple mm to remove on the section height and it is down to final dimension.
No photos worth sharing.

Derek

Coming along nicely. With four of them I imagine this joint is going to feel like it was welded together In other words, it will be tight!

Brian wrote: ↑

Sun Jul 09, 2017 12:30 pm

Coming along nicely. With four of them I imagine this joint is going to feel like it was welded together In other words, it will be tight!

Cue the Bob Seger(?):

https://www.youtube.com/watch?v=9b4cW9sx47A

Hah, indeed.

I assume that is why you prefer these joints to square pegs? These being a bit easier to fine tune exactly how much tension is applied, where square pegs being more of a guess.

The peg is a weaker link as it is subject to bending and shear loads, while the shachi sen is subject only to compression perpendicular to grain. Shachi sen make for a much stronger connection, and take advantage of the ramping effect as well, which makes them as you note, more tunable.

Thanks Chris, I assume both components are made stronger since the shachi would need to shear the entire section of wood to fail, where the pin really need only split out the smaller section of short grain.

I think pins which break the relish portion when under tension are perhaps joints in which the tenons and relish should have been longer. Pegged connections are essentially best at dealing with compression, with the peg a mere keeper and device which allows for seasonal movement.

Under severe tension loading, a shachi-sen joint can actually suffer from the pins rotating in their mortises and inducing tension perpendicular to grain in the receiving pieces and thereby splitting them - this seems to happen well before parts of the receiving stick shear off :