Help with half lap dimensions for a box lid

[Tony Shea]

The title of this thread is wrong, not sure how to edit it. As was pointed out I am referring to a bridal joint. Def not a half lap.

I am currently helping my girlfriend make a box for her first project. We chose to base the design off of Krenov's box in Cabinet Maker's Notebook. We are planing on a small raised panel lid in style of Krenov's raised panels which basically are just a rabbeted panel.

We plan to use the bridal joint for the frame of the lid but am having trouble deciding on what dimensions to use for the joint. We are using 1/2" material. Typically i use the law of 1/3's with mortise and tenon or half laps. But a 1/3 of half inch doesn't work very well with my chisel sizes or any tool I would use. Please help us lay this joint out.

I have to keep in mind the width of the groove for the panel as well as this will be the same thickness as the mortise/tenon. Some reason I just can't wrap my head around this thickness of material. I was originally thinking 1/8" thick groove/mortise/tenon. But this seems somewhat small to me.

[Alan Schwabacher]

If you really mean a half-lap joint, you'd make it half the thickness, or 1/4", but it sounds as if you actually want to use a bridle joint, where you would want to divide the thickness into thirds. That does get pretty thin, though if you have a 1/8" chisel you could use it. It should be strong enough for a box top, particularly if the shoulders fit well. That's because the tongue is then only in tension, and you are not likely to apply enough force to pull that out. An ordinary mortise and tenon joint would be reasonable too, as I don't think a bridle joint saves you as much work compared to the M&T when you cut it by hand as it could with power tools.

I suspect that the simpler half lap would work fine as well.

[Tony Shea]

I apologize, I meant a bridal joint. The reasoning behind the bridal joint is more for looks than anything else. A regular M/T joint is an option but really was going for the visible joinery on the bridal joint.

[Pam Niedermayer]

This is why I work in millimeters, think of 12mm rather than 1/2", works out to 4mm per.

Pam

[Jon van der Linden]

Use what looks best. Since you're already looking at Krenov's books, you can see what proportions he used. I wouldn't go too far from the 1/3 ratio. There's no reason to use measurements, go with ratios and proportions. The size of your tools is irrelevant (as long as you have one small enough), mark out the work and work to the layout.

That's the beauty of hand tools, you don't have to work to dimensions, you get the flexibility of working to what's optimum.

[Jim Neeley]

Tony,

I'd use 3/16 for the "tenon" with 5/32" for each "shoulder". That's leave them within 1/32" of equal while leaving the tenon with the extra strength. These 3/16" mortise (and bevel edge) chisels are available from L-N, amongst others.

Jim

[Damon Stathatos]

His tenons look to be more towards 50%.

His raised panel looks to be very shallow. It almost looks as if the groove for the panel is offset towards the top because the hollow from the bottom of the lid looks deeper than that of the top's.

With one-half of the lid resting proud of the box, it's almost as if he was trying to top-weight it, accentuated by pushing the panel up, more towards the top. With the shallow raised panel and the proud lid, the finger pegs (pulls), which are oriented towards the bottom edge of the lid, are more able to be 'absorbed' by the body of the box than if it were a more normal proportioned raised panel lid.

I'm not sure if I've gotten it completely correct but it sure looks this way to me.

[Tony Shea]

I beleive we decided to go with 3/16" tenons and leave 5/32" on the edges. Seems to strike a better balance of strength and looks. I'd go with the metric system but just have no measuring instruments that measure metric. Thanks all for the help.

[Jon van der Linden]

Krenov's proportions are very close to if not exactly 1/3. Photographs are deceptive because of lighting, reflection, and of course because the edges are rounded. Because of the rounded edges you'll think the tenon portion is larger than it actually is unless you see the real thing.