Mortises and Tenons

No bookwork or e-mail to tend to this morning so I got an early start. The machines were set up and ready to go, so I got right to it. Step one today was to cut the tenon cheeks – the long faces on the side of the tenons. I used my shop-built tenoning jig for this, it isn’t pretty but it does the job. All it has to do is hold the rail steady in an upright position and at the right distance from the blade. The jig sets over my table saw fence, so the fence is used to set the distance from the blade.

Next I take these pieces to the band saw and cut away the end pieces. On the top and bottom rails the outside cut is deeper than the cut I make on all interior edges, so the scrap piece does not fall away. I complete the cut with a coping saw and trim up the shoulder with a chisel.

When all the rails are done I can stack the pieces to check the lay-out and coloring. The tenons will fit inside the stiles once I cut the mortises. To lay out the mortises, I lay the rails onto the parts and mark the mortise locations directly from the tenons. In a perfect world I would be able to simply use measurements from the design sheets to lay out the mortises, but this is not a perfect world and I get better results doing it this way.

Then the stiles go with me to the drill press fitted with a mortising attachment. This clever device drills square holes using a four sided chisel with an auger spinning inside it. When properly set up and tuned, it yields some nice clean mortises with a minimum of fuss. I’ll need to clean out the bottoms just a bit by scraping them with a narrow chisel, but otherwise these are done.

Next I spend some time fitting the tenons to their mortises. Got get a precise fit I always cut the tenons just a hair too thick and work them down to a perfect fit. Trying to go for perfection on the first pass sometimes leads to a few tenons that are too thin. These can be repaired by gluing very thin shim stock to the tenon then shaving them down to a perfect fit, but that takes much more time to do than it does my way and seldom does everything turn out perfect the first time. Maybe if I bought a commercial tenoning jig I’d be able to have that confidence… maybe not.

A perfect fit on a mortise and tenon joint is one that will go together using firm pressure by hand. If you must hammer it, it’s too tight and once you put glue on it you will have a devil of a time driving it home. If the parts slide together with little or no pressure it’s too loose and wood movement will cause the glue to fail and the joint to break. You’ll need to shim and re-work that one. It may be necessary to use a mallet to dismantle the joints or to put together a full assembly, especially a complex one like this back panel. But you should not need to use excessive force even them.

Now it’s time to cut the panel grooves. These grooves will run around the inside edges of rails and stiles to house the panels. The grooves in the rails and the grooves in the stiles must match up perfectly or the parts will fit too tightly because the will bind one another and gaps will open up around the panel in the corners. So, I center the groove and test it using a piece of scrap stock the same size as the rails and stiles.

Cutting the grooves in the stiles is a special challenge because the groove does not run end to end like it can on the rails. So I mark the table saw insert where the blade breaks the plane to the table top, and mark the stiles as to where the groove must stop. Then I can line up the marks on the stile with the marks on the table saw and drop the stile down onto the blade, push it through to the other end and when that mark lines up with the edge of the blade lift it off the blade. Featherboards make this just a bit safer. When done, they look like this.

With the framework grooved I fit it all together again and check the alignment of the grooves. Very good. So I trim the filler panels to size, sand them a bit and pop them into their places. I don’t want these panels to rattle, so again I go for a snug fit; they don’t just drop into place, it takes some working to get them to fit properly. Not so tight they won’t go together, but not so loose that they will rattle later on. These are floating panels, they can not be glued in place, they must be free to expand and contract as humidity dictates.

When all three panels are completed I stand them together and take a look. No glue has been used yet, just friction. I will need to do some more milling on the side panels for the front grid tomorrow, and the panels need to be stained before I can permanently assemble the framing so strips of raw wood don’t show if the panels shrink up. But before I can do that, Nance needs to tell me what color they decided on. And we may need to make up some color samples to help them decide. So, no permanent assembly yet.

See you tomorrow!

Doug