How to cut an offset lap joint for a picture frame?

[Ed Mitchell]

Hi all,

Going through Matt K.'s book on kumiko, he has some instructions on how to make an offset lap joint for a frame, but his instructions are unclear to me, so I'm hoping someone has a link to their favorite demonstration / article about this joint. I can't find anything on google nor on this site, maybe the joint has another name I should search for? It's a lap joint for a picture frame, but the unequal sizes of the laps allow the frame to come together such that the rabbets aren't visible when the frame is assembled, and it can all be done on the table saw.

I understand only the beginning steps:

get the lumber milled and to final dimensions
cut a rabbet along one long edge of each of the 4 components
then I'm to cut differing size laps, but I'm not sure how to determine which joints get what procedure, nor what the procedure actually is.

Thanks for any help, it's not important, I can just do a normal lap joint and then cut the rabbet for the artwork with a router or by hand, I was just hoping to learn a new and perhaps better technique.

[Dick Mahany]

I have used several techniques for cutting splines and double lap joints on a tablesaw. One uses an auxiallary tall fence and a simple 45° backer that slides along it to guide the piece. Another possibility if you will be doing many of them is to build a fixture that will pass the parts over a table saw blade.

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[tom lucas]

Are you looking to do half-lap miter joints. Lots of good info like https://www.youtube.com/watch?v=WQLItyARaAw

I like using them because they are simple and pretty strong, as long as you don't mind the edge view reveal of two pieces of wood.

[Ed Mitchell]

Are you looking to do half-lap miter joints. Lots of good info like https://www.youtube.com/watch?v=WQLItyARaAw

I like using them because they are simple and pretty strong, as long as you don't mind the edge view reveal of two pieces of wood.

Thanks, Tom. No, half-laps, whether mitered or 90 degrees, are really simple because they're all identical. Matt Kinney's book talks about a method of cutting a type of lap joint he calls "offset" lap joints which have the advantage of hiding the rabbet for the artwork (when viewing from the outside of the frame one cannot tell that there is a rabbet) and also can be cut entirely at the table saw. They are like "normal" half laps, except in a "normal" half lap, where all the laps are identically sized, the offset laps are of different sizes. Matt's verbiage couldn't convey the process to me, and neither did the illustration, so I was hoping someone had done them already and could talk about the process in a bit of detail.

Oddly, I can't find any resource online which talks about this joint. The truism says there's nothing new in woodworking, so I'm sure it's been done a million times and probably documented in many web pages, which makes me think the joint might be more commonly known by another name. It can't be that complicated, but sometimes experts have great difficulty explaining things to non-experts. I'll probably figure it out on my own just through trial and error this weekend, but was hoping to skip that part...

[Jeremy Headrick]

I also bought Matt’s kumiko book and was unable to understand how the laps were marked and cut. Where you able to figure this out or find any other tutorials or information? The only thing I found in my web searches was this thread.

[Brian Runau]

Are you looking to do half-lap miter joints. Lots of good info like https://www.youtube.com/watch?v=WQLItyARaAw

I like using them because they are simple and pretty strong, as long as you don't mind the edge view reveal of two pieces of wood.

Tom, works well cutting non defined length, but without positive stops how would you get matching lengths for pieces? thanks brian

[Kevin Jenness]

The laps on both pairs of frame pieces are cut with a dado blade from opposite faces. The dado height is set to match the location of the rabbet, and will be different for each reference face if the rabbet is not centered in the stock. The shoulder length on the un-rabbeted front face will be the full frame width, while the shoulder on the rabbeted face (the back) will be reduced by the rabbet width.

The author does not detail the mounting of the kumiko in the frame. The rabbets in his frames accept a fabric covered backing and the fastening of the kumiko array itself is left to the imagination. Some examples of furniture shown suggest that the outer kumiko members may be wider or the horns left on and held in with a back panel or stops, but the wall panels appear to have the kumiko flush or almost so with the front of the frame. In shoji work the kumiko would be tenoned into the structural frames.