The Shinto temple, er, table.

The time has come,  the Walrus said, to make a table to support my grinders. I have two of them. I have far too much space in my hallway for a computer. It is currently held up by a door on sawhorses. Far too wide. So I decided to shorten it up and stick in a table wide enough to hold my wet and dry grinders. I had originally decided to use power tools on it. And of course I am using other people's offcuts, i.e. scrap. This means so-called "2x4 lumber." A few moments with a ruler will convice you that modern 2x4 are nowhere near that dimension. This is a way the lumber companies can get a little more lumber out of a log, at your expense. The modern 2x4 is something like 39mm x 88 mm give or take a whole millimeter. Convert it yourself if you want; I don't use RGU. But its not even a 2:1 aspect ratio.

Now my bandsaw will not take the 88mm width -- it is 3" or about  77mm. In retrospect there is a way around this; I could have "housed"  the joints -- but at that point I decided to build this thing by hand tools only. I am glad I did. I learned a great deal. Not the least, how to operate a Japanese ripsaw correctly. I am grateful to Roy Underhill on pbs.org for some very useful tips. But I can now rip to within a half-millimiter over a 90 mm length. I could not do that when I started this project. Unfortunately I did not document it. I thought it was going to be a one-morning knockout project. I will have to do a future post on how to do these joints, this is really timber framing and a useful art to acquire. This is a lot like building a Shinto Temple. This is an art which requires master carpenters. No master, I, but at least I  learned something. I cut whole thing together piece by piece. When all was done I put it together. And it fit together.

Layout is 90% of the problem in timber framing. For this you need a very acccurate pencil. The Japanese use a bamboo brush, or sumisashi. I found out that a "Sharpie" thin marker works very well indeed, as long as you hold it properly against the square.The tip of the Sharpie is less than 1 mm wide.

I am really glad I did this the hard way, and I hope to do a post on how to cut these particular joints in the future -- since I did not document this project. Today I pegged these joints; hopefully I'll cover that in the future.

A Japanese-style mortise gauge

To some of my readers, perhaps only the word "Japanese" makes sense in the title. No matter. All will be revealed in good time. A mortise gauge is a device used to mark out the sides of a mortise. A mortise, in turn, is a sort of trench excavated in wood. In this trench fits a similarly shaped peg, the tenon. M&T joints are as old as the hills. This summer's program includes a brand-new machine storage barn. I am determined to do it timber-framed. None of this nailing commercially milled lumber together. We will cut mortises and tenons and peg the whole thing together. It will last much longer than I will, unlike the ticky-tacky boxes they call "houses" these days.

Anyway, a mortise gauge is a layout tool. It will lay out the long sides of the mortise. If this is perplexing, stay tuned. We begin with the slider; it needs a rectangualr hole. I am using wood from a footstool that had fallen apart and been deconstructed.
What we have to do is cut a rectangular hole in a piece of wood. This is the way I did it. First, the dominant dimension in the scrap wood was 19mm, or 3/4" RGU. So we drill overlapping holes 19mm wide, and chisel out the rest so's it's rectangular. Behold the result above. A reasonable rectangle. Now we make the arms. These are nominally 19mm square cross-section, arbitrarily long. I could have made them much shorter than I did, but here is one of them:
That's one arm. The other looks just like it. In the middle there is an aluminum separator strip. This is to keep the arms parallel. The arms have to be planed so they are a tight, but not impossibly tight, fit into my rectangle. It is much easier to plane the arms than to enlarge the rectangle.
When both arms are in it looks like this:
Now, in the arms go the cutters. These things score the wood, and prevent tear-out when you actually make the mortise. I made them out of an old hacksaw blade (never throw good steel away). They were annealed, ground to shape, hardened and tempered. Then they were sharpened. Tedious but necessary. Now we had to make a slot in each arm to accept the cutter. I did this by drilling 1.5mm holes in a line and cutting out the intermediate stuff with one of my miniature mortise chisels (handmade, of course). When we got this done we had a respectable-looking Japanese-style mortise gauge.
There were some details, in which, of course, the Devil always resides. I epoxied copper rubbing strips to the inside of the rectangular hole, which, by the way, is itself a mortise. A through-mortise to be exact. The arms require wedges to hold them in place. But on the whole I am very pleased with my gauge. It cost nothing. Perhaps in the next episode I will cut a mortise for you to show you how it is used, and it has been used, and very, very useful it is. I have a commercial mortise gauge, but this one is much better, because it scores the wood instead of scratching it. This helps a lot; prevents tear-out when you actually cut the mortise. Next episode I may cut a mortise for you to show how it is done.