In my last post, I detailed my plans for a lid over the stretchers on my workbench base. I re-sawed and milled the lumber needed and started cutting the joinery for the wedged mortise and tenon joints of the frame. I ended at a sort of arbitrary place in my post, but this was due to only having gotten that far on the day I wrote it. Now I need to finish making the frame. I was quite busy outside of the shop last week, and unfortunately, only managed one blog post. Hopefully I’ll do better this week.
The last step I had taken in my earlier post, was to cut away the waste wood from the tenons on the ends of the rails. I laid out the cuts with a knife but used the table saw to remove 99% of the wood. This left a small amount of wood that needed to be chiseled away to leave a clean stub tenon shoulder.
A few minutes work and all six tenons were cleaned up.
Using the same setup that I used to cut the grooves in the stiles, I cut identical 5/8″ grooves centered in the rails. The center rail needs a groove on both sides, but the two side rails only need one groove on the edges that face inwards. I put a bit of blue painter’s tape on the outside edges to remind me not to cut there.
Cutting this 5/8″ groove along the full length of the rail also serves to reduce the width of the stub tenon and the trough tenon. I accounted for all of this when I laid out and chopped the mortises.
The grooves in the rails will be housing the end grain edges of the panels that I have yet to make. What I mean is, in the picture below, imagine that the panels will have grain running left to right. Since wood will not expand or contract significantly along its length, I cut these grooves 1/2″ deep and will size the panels to almost fill them completely. I’ll cut the panel just 1/16″ under size.
The grooves in the stiles (previous post) were cut deeper (3/4″), to allow the 20″ wide panels some room for expansion.
I was happy with how this came out. Quite crisp and neat.
The only thing left to do in sizing the tenons is to cut off the outside edges. If this step was not done, I’d be creating a bridle joint not a through mortise. In my design and layout, I allowed a setback of one inch from the end of the stiles. I also left the stiles over-length and will trim them back flush after final assembly. Both of these things were done to prevent the end-grain of the stiles from blowing out when I hammer in the wedges in the through tenons.
To mark the 1″ setback, I set my adjustable double square to 1″ and in combination with a knife, used it like a marking gauge.
I darkened the line with a pencil.
Using a tenon saw, I cut down along the waste side of this line stopping before the stub tenon.
I switched to a fine crosscut saw, and trimmed the trough tenon off at the point where it meets the stub tenon.
Here’s the shape of the final tenon.
I realize that this may seem a little overly complicated, so I thought I might provide a little explanation of why I did it this way.
To start, I had to think about what I was trying to make. This is going to serve as both a lid for the compartment below and as a shelf. I’d only be fooling myself if I said things weren’t going to get stacked on it. It needs to be able to support some weight. I wanted a surface that was fairly flat, so a raised panel was out. I decided upon a flat panel that would sit completely within the groove in the frame, i.e. no rabbets around the edge of the panel to go into the groove. I also wanted to cut wedged trough mortise and tenon joinery, simply because I thought it would work here and I have never done them before.
In a normal mortise and tenon frame, the tenon would all be the same thickness and likely wouldn’t go through. This might, or might not, be draw bored / pegged. Mine has two different tenon thicknesses, why? I thought that if I used the 5/8″ thickness and went all the way through the stile with this, it would be too weak. I’d have a 5/8″ mortise with only 1/4″ wall on either side of it, not the preferred 1/3 : 1/3 : 1/3 ratio of the ideal through mortise.
Conversely, if I kept everything at only the 3/8″ thickness of my through tenon, then my grooves and my panels would also be 3/8″. While this allows for better through mortise and tenon layout, I felt that the panel ought to be thicker than only 3/8″ if anything heavy were to be placed upon it.
So… I compromised. A 5/8″ panel, groove, and stub tenon, and a 3/8″ through tenon. It was more work to be sure, but I think that it accomplished everything that I was trying to do.
With all of the frame joinery cut, I had to fine tune and fit each joint to ensure that it closed completely and with a nice tight shoulder line.
Below you can get an idea of how the joint goes together.
I left fairly deep knife lines to show where the horns will need to be cut off after assembly.
The tenons came out OK, but the mortises are a little sloppy. I don’t think that the tenons will perfectly fill the mortise and a little, tiny, wee bit of filler might be needed after the edges are planed flush. We’ll see.
With all the joints finessed, I did a test fit.
So far, so good. Now I need to go back to my ever decreasing pile of air-dried douglas fir and find some wood to make up the panels. Book matched doug fir panels? Why not?
– Jonathan White
Very thoughtful joinery design, Jonathan. Given that your glued up panels will be load bearing, have you considered reinforcing their glue joints with splines, or do you think that might be overkill, in light of the rather short span of long grain between the rails? Regards, Larry
As much as I love to overbuild everything, I hadn’t even considered splining or biscuiting the panel. I’m using Titebond III and in the past have never had problems with it, especially when gluing long-grain to long-grain. The wood usually fails before the glue line. If any weight is placed on one of the panel boards, I think it will be spread to the adjacent boards without breaking the glue line.
What gave me a little more concern was the 1/4″ of wood that remains on either side of the 5/8″ groove in the rails and stiles. When laid flat, this 1/4″ is essentially holding the panel and everything placed upon it. I hope this won’t be an issue.
Thanks for your thoughts.
All the best,
Jonathan, that 1/4″ strip of wood remaining on the bottom of your rails and stiles might be less at risk of breakout were you to use a 7/8″ thick panel with a 1/4″ deep rebate on the underside (only), giving you a shoulder against which the rails/stiles edges could find some lateral support when under vertical load. And that would still give you the “recessed” look on the top surface of the frame and panel unit. I think Schwarz takes a similar approach on the anarchist tool chest lid….perhaps because the chest is also made to function as an occasional worktop or seat. Good luck. Larry