Better cross halving joints

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4DThinker
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Better cross halving joints

Post by 4DThinker »

I teach furniture design, and often a student project requires cross halving connections between stretcher or other parts of the design.
While straight, perfect cross halving joints can be cut using several tools in the shop as well as on the CNC, the typical result is a close fit that if tight tends to scrape off finish and a loose fit will leave the joint with some slop/play in it.

I've come up with a simple wedging alternative that slides in easily, but wedges tight when completely closed. The attached sample I cut to show a student. Both sides of the joint are identical and can be cut from the top side. The fluting tool path ramps the face of each joint half, and the slot is cut with a matching taper. I've cut this joint a few times now on different student projects. It works best when cut in stable, uniformly thick sheet goods. Hardwood isn't ideal for this joint as length vs width/thickness expansion rates can make a joint fit one day and not the next.
Ramped lap joint sample.jpg
4D
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ramped lap joint.crv3d
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scottp55
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Re: Better cross halving joints

Post by scottp55 »

May have a use for this 4D.....Can you post it as a .crv please?
scott
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4DThinker
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Re: Better cross halving joints

Post by 4DThinker »

scottp55 wrote:
Sat Sep 18, 2021 3:54 pm
May have a use for this 4D.....Can you post it as a .crv please?
scott
Yes I can.
4D
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scottp55
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Re: Better cross halving joints

Post by scottp55 »

Thank you kindly Sir :)
scott
I've learned my lesson well. You can't please everyone,so you have to please yourself
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Daniel S
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Re: Better cross halving joints

Post by Daniel S »

Thanks for the file. I will use that in a project for my granddaughter.
Dan

4DThinker
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Re: Better cross halving joints

Post by 4DThinker »

Always happy to contribute to the vast knowledge base of joinery solutions. This semester project is to design a project that can be broken down to fit in 1/3 or less the assembled volume. Most classic woodworking joints are not intended/design to be knock-down. I've been using the tapering of tenons, embedded square nuts, tapered dovetail slots, etc., to increase the options over the standard catalog of knock-down hardware. This wedging halving joint can be tapped tight, and tapped loose again with no glue needed so long as gravity will not be pulling the boards apart.
4D

Onetrack
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Re: Better cross halving joints

Post by Onetrack »

Hello 4D. Nice joint! What's the purpose of the "ramp full length of lap" toolpath? Also, the "half slot" toolpath is an irregular shape. How does that help? Thank you.
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4DThinker
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Re: Better cross halving joints

Post by 4DThinker »

Onetrack wrote:
Tue Oct 12, 2021 2:09 pm
Hello 4D. Nice joint! What's the purpose of the "ramp full length of lap" toolpath? Also, the "half slot" toolpath is an irregular shape. How does that help? Thank you.
I'm teaching a furniture design class, and the project assignment required is to design a project that knocks down to 1/3 the assembled project to 1/3 or less the assembled volume. As most classic joints are not design to come apart after being assembled without wear and tear eventually I've been contemplating how to make a few that with slight modification can slide together with little or no wear yet be tight when finally closed.

The single fluting line that runs the full length over the slot is to continue the ramp over the part of the slot that is tapered to fit on the ramp on the other half. The first time I made it I made all the fluting line run across the board but if the slot was cut first they just cut air. It is just me trying to eliminate any bit travel time that isn't needed. Technically the area over the slot doesn't have to be tapered, but it would have to be lowered to match the height of the bottom of the ramp.

4D

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