With the lumber processed and the leg blanks glued up and dimensioned, it was time to turn to joinery, specifically the sixteen mortises for upper and lower stretchers.
When I first shifted to hand tools, I used a hybrid method for cutting mortises, which is an easy way to keep the mortise walls vertical and it is faster, at least for me. Variants of it have been around since at least 1945. The method is to drill out the mortise on the drill press and then use chisels to finish it. If you trap the leg between two fences, only the top and bottom of the mortises need be marked:
The overlapped holes drilled to depth with a forstner bit the same width as the mortise provide a precise guide for the chisel work. I have been reluctant to use my regular bench chisels for this chopping, so I use these Lee Valley chisels with butyrate handles and they hold up fine:
I made the tenons in the usual way, using knife walls, a tenon saw, a router plane and a spokeshave to chamfer the ends of the tenons. I've learned the hard way to make the tenons very tight the first time they go in the mortise because they tend to loosen up when they have been in and out a few times. There's little danger of splitting these legs. I have also found that if you make them "too tight" at first, it gives you the chance to make minute adjustments in the walls of the mortise if necessary for both shoulders to close tightly. I think this is not the way you are supposed to do it, but it works for me. The advantage over using a shoulder plane is that it give you a chance to align the stretcher properly.
I would like to get to the point that I can chop out mortises quickly entirely by hand. My reservation has been not being sure I could keep the walls perfectly vertical. Paul Sellers has added a simple, shop-made guide to his method for using a bench chisel to chop mortises. You put the side of the chisel against the guide while chopping and then also use it to pare the wall of the mortise when you are done. It seems to me that a mortise chisel is inherently more stable than a bench chisel for chopping mortises, so, if you are going to use the latter, a guide seems necessary. I am going to give it a try.
If you use bench chisels, it is better to use P.S. method for mortising. He made a video where he is mortising behind a glass to show what happens. You will notice that he doesn't use brute force. Light "tap tap" and stop when the sound changes to "thud". It is the chisel bevel which pushes the wood and shears it. Only the quantity of wood corresponding to the "thud" needs leveraging; which is not enough to break the chisel.
ReplyDeleteP.S. is always advocating sensitivity.
I have used this method with no name Chinese chisels from the flea market without problem.
The use of the guide needs concentration to push the chisel against it each time you move the chisel. The guide must be strong enough to avoid flexing. the surfaces bearing on the piece and the surface on which you register the chisel must be parallel (it seems obvious, but don't do a quick and dirty guide. Don't ask.) And of course the piece must be squared.
https://www.youtube.com/watch?v=q_NXq7_TILA
Sylvain
Sylvain,
DeleteI don't know about you, but when I do the tap tap tap I don't get down to depth nearly as fast as Paul Sellers does. I don't think it has to do with sharpness, but rather not levering out waste sufficiently as I go.
Andy, I've used the Sellers guide and while it can work well, I had some problems with it. The front jaw of many vise is at a slight angle so the top is closer to the back jaw. This angle interfered with my guide as it clamped the guide at an angle to the stock I was mortising. When I use this method now, I verify that the guide is square to the surface of the stock with a small square.
ReplyDeleteNot too long ago I read a blog by Dennis Laney (A Woodworker's Musings) and he mentioned a method that I've been using lately. Instead of sitting to the side of the workpiece, he aligns the workpiece with his eye so the mortise's length is in the line of sight. It's easier to determine vertical that way as you have the board being mortised to guide you. Though I have found it's tougher to position the chisel accurately.
But like you said above about fitting tenons, whatever works for you is good.
That seems like a good idea and, as I thought about it it occurred to me that I could set a square up next to the mortise as a further visual reference.
DeleteMaybe the tap tap isn't enough with the mallet you are using? I would think that mallet is better suited to carving or precision work.
ReplyDeleteP.S. goes twice as fast as I do. So I have just checked on the Thorhammer site, his nylon-head hammer is 650g while my no-name one is 334g.I should buy a heavier one.
ReplyDeleteSo, "light tap" has to be taken with a pinch of salt. The "thud" would also be heavier and that is what makes the mortise progressively deeper.
Sylvain