The lumber for this weeks joint from Project Mayhem 2.0 started as a small tortured little log. Not only is there a ton of twist, but bow as well. Half of the fun for this joint will be watching what it does as it dries. I don’t have anything to seal end grain at the moment so it’ll be a fast and hard drying for beam pieces after they are cut to length.
This was also the first real opportunity I’ve had to run my smaller maebiki-oga. I can tell it still needs a fair bit of work to get it cutting properly. Not enough set, my only saving grace was the small size of the log that kept the cut from going too crazy.
Planing green lumber though, man that is nice. Heavy shavings came off with ease and I had my stock squared up in no time. Finally a photo so that you get to see more than my hands and feet!
Here is the layout for the rod tenon side of the rail connection. Lots of wood to remove! You’ll feel like a real sawyer by the end of it.
And the other side has a receiving mortise for the rod tenon that goes through the post, as well as a small stub tenon at the bottom. The cogging/haunch either side of the tenon is a new twist, and I can see how it would be a good thing to increase the surface area that resists downward forces as well as guard against twisting.
The post mortising layout is simple, but belies the fact that there is also an awful lot of wood to remove.
I started by cutting the step on the beam that receives the rod tenon. For this joint I was using my 240mm ryoba, which felt a bit small at times when cutting the full width of the stock. It definitely had issues with gullet clogging on this resinous wet wood.
I cut most of the cheek on one side of the tenon before I realized that I was missing the lines on the shoulder that allow the tenon cheek cuts to be finished.
After adding the missing lines I ripped down to the second shoulder line on both the tenon and the haunches on the side. From there the rest of the waste was chopped out and the layout completed for the mortise that receives the opposing rod tenon.
The arrangement of the sachi-sen in relation to the draw pin was not clear in my mind, so I stopped the cutting to finish the layout. I still don’t think I have everything in quite the right place, but with this arrangement the wedges are driven first and then the square peg locks the wedges.
Both sides of the slot for the sachi-sen are tapered such that the total taper is 1:12. It was quite convenient for me to add a line on the top of the beam that I could re-set my bevel gauge to when it came time to make the wedges.
My brace is a total piece of junk, very difficult to use accurately, and I broke one of the jaws during a stupid fit trying to use it as a tap wrench. So the mortise was chopped with a bench chisel and the slots for the wedges pared in with chisel as well.
The beam with the rod tenon was next, but I was getting tired and zoning out a bit so I forgot to take many pictures. Rip away!
And voila! It is cut. I wish…imagine if this was an 8×12″ beam, now that would be some cutting.
Its pretty easy regardless of the specifics of how your wedges are dimensioned to determine the thickness of stock needed.
I noticed the last time that we used sachi-sen that things looked a little miss-aligned after the wedges were driven. I had a line on the rod (which you can see on the right) which represented where the tenon meets the opposing beams shoulder line. This was my reference for a slight offset of 1/32″, same concept as offset for a drawbore. With small little practice joints like this I have the luxury of a trial assembly to see how accurate I was marking the offset from the shoulder line.
Chopping the mortise was easy in this green lumber, but getting the waste out was not. That’s the way of it will all chisel mortising, the cutting is easy and then you spend half your time cleaning.
I ended up with live edge corners on the beam pieces that I felt would look wrong if I didn’t scribe to fit. That’s the reason why the tenons were cut before the mortise.
The stopped rebates that house the beam haunches came last. I was getting seriously fatigued at this point and cut off one of my scribe lines without noticing.
I have a nifty little router plane but I do these exercises with as simple tools as possible to better reflect the conditions I’d actually be working under if I were to travel and cut a timber-frame. Paring blocks are great! Accurate, pretty fast, and dead simple.
The scribing on the side I didn’t over cut came out great, it looks very craftsman like. This blue stain lumber takes a nice polish from the plane as well, I can imagine having a structure made from it would be a pleasure to the eye.
I did a better job with the wedges this time, even though it took two tries to get the proper fit. I’ve really nailed down what will work for me and I’m glad to have another chance with the sachi-sen. The measurement for the width of the wedge at the top is between the obtuse angle corners of the parallelogram. For the first pair I cut I measured across the acute angle corners and the wedges were too loose.
I thought that I would make the width of the wedge 1/16″ more than needed but that was wrong as well. This is how much stuck out after lightly seating them and I was a dumbass and tried to drive it home anyway. The offset of the slots mean that the top of the wedge width should be the finished width of the slots after the offsets are pulled together, no need for extra relish on the wedge.
They drove about half way and then no further, with a small split starting in the rod tenon on the left side. I tried to get them to back out by tapping around them with a wood block and hammer, but they were seriously, um, wedged in there. It really removed any doubt in my mind about the holding power of wedges. I had to grab the top with a c-clamp and hit the clamp with a hammer, really hard, to get them free.
I know how much of the wedge I want sticking out the top after it is driven fully to depth, 1/8″. After the sweating moment getting these buggers unstuck I sat down for a moment of reflection and thought it through. If the ratio is 1:12 and my offset for the joint is 1/32″ how far down will the wedge travel to bring the pieces into alignment? Twelve times 1/32″ is 3/8″, plus the 1/8″ of extra to stick out the top tells me that the wedge should seat down under hand pressure with 1/2″ remaining before driving in with a hammer.
After planing down the wedges to make the necessary correction I met with success. The offset didn’t pull in completely, and my wedges still look a little sloppy, but the joint is solid. And now to really kill this joint…
Back comes poorly made $20 brace to bore a hole for the square peg. Why is the peg square anyway? I’ve never read an explanation for any advantage over a round hole. I bored through half way from either side using a small square and my layout to keep the bit in line.
And with a good deal of fuss the hole was chiseled square. I used a screwdriver to knock the waste out, but a strike through chisel of the right size would have been better.
I gave the leading 3/4″ of the peg a very light taper on all four sides so that it wouldn’t blow out any end grain exiting the other side of the hole. My pin was also planed to be a tight fit on the end grain and a running fit on the long grain on the hole.
I left the pin protruding slightly from either side and chamfered the edges after trimming to length. This is a handsome joint, is it not? Took all day and then some of this morning to cut, including ripping the 4×4 beam.
Yesterday was a twelve hour work day to get this far and the theory part of this weeks etude remains, but for tomorrow after a day of rest.