Saturday, June 20, 2015

Project Mayhem, joint #1....Sumitome hozo sashi ( Part 2)



A continuation of the Japanese timber joint, Sumitome hozo sashi.

After cutting as much as possible with the saw, it is now time to pull out the chisels and start removing everything that ISN'T the joint.



Sharp tools are key. I would've listed sharpen tools as tip #1, but even my penchant for redundancy has limits. Always sharpen.



One small problem though. I got so excited to be using the chisels that I forgot about the haunched portion of the tenon.


It's the part that you don't see, haha. Otherwise this half of the joint is looking rather nice.

Do you have something that you forget to do so often, that you start to question the health of your brain?


Save time and effort by drilling out the waste, then pare to the line.....Tip #7.

The pine dents so easily. This is the bottomed mortice of the vertical stub tenon.


I should be more careful when digging out the chips from the mortice.

Time for the first fit.








At least I nailed the mitre ( small comfort). Way too loose everywhere else, though.

I spend the next 30 minutes fiddling with the joint to see how much it can be improved, but there is only so much that you can do.



A small saw with no set to the teeth is handy for kerfing, trying to draw the two halves of the joint closer together.






At least the joint is square. It's not too horrible for a first attempt.

On Sebastian's drawing the tongue that is shown here to the left, the part that is covering the end grain, is drawn as tapered. I took the easy way and cut mine straight.....a small thing, right? After cutting this joint, I would like to try again, but cutting the tongue tapered as intended. The straight tongue is mostly a one-shot deal, it's either good....or not. The benefit of the taper is that the joint would draw tighter as the fit improves. You would have more to work with.

Interesting thing here. The primary tenon has a small kerf cut into the end, to receive the wedge. When I drove the wedge home, the joint initially tightened very slightly, but then proceeded to open up.






I drive the joint apart to see what's going on inside, and you can see that my wedge was too long and thin. The tenon has split, mostly because I had cut the joint so loose that there was ROOM to split. A properly snug tenon probably would've been fine, but....

A second vote for the tapered tenon.....It would be stronger, and better able to stand up to the force of the wedge.






I cut a new wedge, much thicker and shorter than the first, and drive the joint home. A few swipes of the plane clean off most of my scribbles.




And then I realize that I made another mistake. I cut the stub tenon mortice too big, haha......ugh. And gappy.

The back side looks a bit better.




Inside is a horror. Funny how big a 1/32 gap looks at this scale.

All told, I spent around 5 hours....square the stock, layout, cutting the joint, sharpening tools afterwards (another thing that I am finally drilling into my thick skull, haha), and taking photos. I estimate #2 would take me 3 hours, assuming that I can keep the cat from trashing my chisels.

After 100 of these things, I might have some skill.



Another realization that I just had now. Two years ago, prior to assembly I would've spread the joining surfaces with Tightbond glue, used clamps to draw it tight, then hammered in the wedge. If it had looked this good, I would've been ecstatic. Now that stuff doesn't even occur to me. Glue....yuck!

Well.....hide glue is still awesome.

After cutting this joint Sebastian asked me my thoughts on the excercise. The idea is that the practice will greatly help us personally, but it is the sharing of knowledge that can be of the greatest benefit. I pulled this out of our discussion......and please excuse my potty mouth, haha.

Much of the gappiness in mine was because I tried to just saw the line, no paring. If I get a poor fit, tough shit, do better next time, I tell myself. You get better at sawing that way, though, haha.

I think that we both made a good effort at our first attempts, yes? For my work, I look at my inaccuracies, the work backwards to find where the errors originate, but it's hard sometimes.

For today, my sawing was quite good. I have been thinking of saws and the mechanics of the ACT of sawing, that I tried to go as slowly as I could stand, feel the teeth cut and try to always keep the blade centered.....not touching the sides of the blade to the wood, ever. When I did that without being too tight in my head, the cut was perfect. Push the saw to cut faster, and the cut went bad. I know this stuff, but my body is dumb and my mind is impatient.

Another thing that has been helping me is to refuse to undercut anything. When I make the cut, I stare...really look at it and then try to pare the surface PERFECTLY flat. I do this by eye, as well as I can, then check against a straightedge. Then I do it by eye again. And again, until I can do no better. My working stamina is generally only 2-3 hours, then I need to take a rest, so that forces me to stop, then come back later. If I use undercut to try for a perfect looking joint, that means that I CAN'T do it right and need to cheat. This puts me in the mindset of wanting to be done. I would rather be decent at joinery and it ends up being way more fun.

You don't need to be told anything, that's not my intention. This is for me, and it is something that has just started working. It is really amazing, almost magical. Wanting to get finished is a misery and only leads to poor work. God, I sound all preachy and shit. I hate that. My point is that I "knew" this forever, it's just that now I guess that I've truly started to see it working. I still can't cut joinery for shit though, haha. That's why this excercise is so necessary for me.

Now I want to dive into that fantastic book you gave me. I spent about 6 hours on the plane, looking again and again. You picked a good joint to start out this study. Not simple, but not as complex as most, from that particular text.

Oh yeah. Sorry....

1) I think most of my errors came from squaring from the edge, but the wood wasn't square enough for perfection. This was kind of necessary, due to the small size of the stock I was using. When I use bigger stuff, I will use centerline ( something that I am only recently understanding the value of).

2) 0.5 mm lead is too thick for joinery of the size I was cutting. I did 1/2 in pencil, 1/2 knife. Knife was far better for this size.

3) My eyesight is swiftly getting worse, and the lighting needs to be perfect for me to see the layout.

4) Shit.....I can't remember #4, haha.

5) Obviously I need more practice.



Also obvious is that I was in the mood for lists.







That Sebastian, taking me to task yet again.......

Here is the third part of the joint, presented in all of its glory.


I left the previously completed joint sitting out in the rain so it has become even more unsightly. Gapsville, man.....Gapsville.

Sharp eyed folks will notice that I have layed out and cut the mortice larger than it was intended.


This side is nice.

This side....



Not so nice, due to the swelling from the rain. Excuses,excuses,haha.

A very cool and interesting joint. Fun too.

Thanks Sebastian!


  1. did you realise you are forgetting the column? There's still some time left...


Like all of us, I am figuring this out as I go, so when you see something that is incorrect or flat out wrong (and you will!), let me know. This is a learning process. Real people and names, please. Constructive comments and questions are very welcome, but hate speak/politics are not! Life (get one!) is too short.

Thanks, Jason