double dado cross half lap joint? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 17 Old 11-08-2011, 10:37 AM Thread Starter
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double dado cross half lap joint?

I've been experimenting with this joint for a knock down table. No hardware allowed. My dado method was to use a narrow setup and flip the boards over to keep it centered....somehow that isn't working as accurately as I 'd like and I get confused whether I'm measuring the slot or the lapping piece. I don't expect an answer or solution, but I'm probably gonna go a 3/4" stack instead of the flip method. I realize I'm makin' it more complicated than just one dado up and one down and interlock the boards, but I see this a somewhat stronger and resistant to racking.

First attempt photos:
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The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #2 of 17 Old 11-08-2011, 11:36 AM
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That's a cool joint!

Looks like it would resist racking better than a standard cross lap.

Lots of... no glue surface.

Scott
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post #3 of 17 Old 11-08-2011, 12:35 PM
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I like it.

Looks like you are doing the dado's with a stack and the half laps with the router. I think I would be inclinded to do both with the router. Guide strips and a bushing for the router, switch the bushing add a stop to get the half lap, maybe need to switch bits too but would keep everything centered. I think I would probably make a "U" shaped jig to ensure the guide strips are the same on both sides of the board.

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If I strive for perfection, I can generally achieve good'nuff, If I strive for good'nuff, I generally achieve firewood

Last edited by jschaben; 11-08-2011 at 12:42 PM.
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post #4 of 17 Old 11-08-2011, 12:36 PM
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Nice joint!
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post #5 of 17 Old 11-08-2011, 12:39 PM Thread Starter
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yeah, it's cool but

everything has to be dialed in spot on, because each time you flip it over to make the dado on the other side, you X2 the mistakes, in my case, or depth of cut. Width wise the dado is more managble, but still requires 2 passes and therefore 2 fence settings. I plan on making 3 or 4 of these so, I'll have to practice, practice..... bill

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post #6 of 17 Old 11-08-2011, 06:59 PM Thread Starter
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Practice...practice....

Like marriage, 4th time is a charm...
Gettin' closer to no gaps or almost perfect:
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The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #7 of 17 Old 11-08-2011, 11:46 PM
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Your sketch looks like your legs are angled in slightly, but your cuts are square. Am I seeing those correctly?

My suggestion is to build a dual-vertical router table with facing bits to run your board through so you don't have to flip anything. Your bits would probably need to rotate in the same direction ('down' on the feed side) for safety and accuracy.
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post #8 of 17 Old 11-09-2011, 04:31 AM Thread Starter
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that's the photo distortion

Quote:
Originally Posted by Improv View Post
Your sketch looks like your legs are angled in slightly, but your cuts are square. Am I seeing those correctly?

My suggestion is to build a dual-vertical router table with facing bits to run your board through so you don't have to flip anything. Your bits would probably need to rotate in the same direction ('down' on the feed side) for safety and accuracy.
The legs are square.

As far as the dados I am considering a router with an edge guide or just a router table.
The most direct way is to be able to center both sides of the dado on each of the legs on both sides. Flipping it over in the case of the legs, not the horizontal brace, means it must be exactly centered on the width. The dado must be stopped the width of the cross brace in from the end as well. These mock-ups don't show that, they are just through cuts.

A self centering router plate like a doweling jig comes to mind.

Anyway it's a entertaining challenge, for me at least.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #9 of 17 Old 11-09-2011, 04:55 AM
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Quote:
Originally Posted by woodnthings View Post
I don't expect an answer or solution, but I'm probably gonna go a 3/4" stack instead of the flip method. I realize I'm makin' it more complicated than just one dado up and one down and interlock the boards, but I see this a somewhat stronger and resistant to racking.
If you don't expect an answer or solution, why post it? Ask for comments and opinions. It's an interesting joint. My opinion is that without glue, if the pieces slide together without being smacked with a mallet, there will be axial stresses to allow some side movement, which will eventually wear out the fit. Unglued joints need some way to be drawn tight to eliminate movement.

Creating that might be easier to use one side guide reference for distance from that side, and use determined spacers for any width variation to the machining. JMO.








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post #10 of 17 Old 11-09-2011, 06:59 AM
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Very cool Bill...
It looks like Japanese Joinery
Are you building this knockdown for the shop ?

Can't wait to see the self centering router guide that you're going to prototype....

Learning more about tools everyday
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post #11 of 17 Old 11-09-2011, 07:17 AM Thread Starter
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Japanese?

I only wish I were that good! I do have a few books on thier joinery and I still don't understand how they do some of them...

Actually it was inspired by a request from the local Art Centrer which needs a simple space saving or collapsible table to be used with some donated glass shelves 12" x 72" for display. I told them I'd make a prototype/mock up and give them a quote for 3 or 4 units. Cost is a big factor as they are non-profit. I plan to use construction 2 x 12's and plane them to uniform thickness before machining the dados, to remove dimensional variations, twist, cup etc. It's still not an official job/contract, so I'm treating it as an interesting joint and possibly to be executed in 2 different hardwoods as a 3 board table. Also inspired by gus's beautiful table posted here a while back. bill

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #12 of 17 Old 11-09-2011, 01:56 PM Thread Starter
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I can build that joint with 3 tools....

OK. Build that joint!...an old TV show name that tune...
Actually without a router or a dado head in the table saw....I could even do it without a table saw, just a circ saw.... Yah, sure.
OK. Here's how: rip all your horizontal braces to 10".
Rip 2 leg braces to 12". cut the up and down dados so they interlock at right angles. Then fill in the side pieces on the horizontals and legs cutting them to fit exactly. BTW I used a table saw for ripping and a RAS for the crosscuts, just 'cause I could.
The side piece material need not be the same thickness or the same material as the core or middle. The core can be plywood or particle board or hardwood, the side fills can be whatever material you want on the finished piece. I used all 3/4 particle board 'cause that's what I had on hand for this mockup.
bill
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The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 11-09-2011 at 05:55 PM.
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post #13 of 17 Old 11-09-2011, 02:29 PM
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That's Cheatin'!

Great idea, that keeps the variables to a minimum.

............................................... ....

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post #14 of 17 Old 11-09-2011, 04:34 PM
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Too confusing!!!! Great work!
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post #15 of 17 Old 11-02-2013, 06:20 PM
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genius
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post #16 of 17 Old 11-03-2013, 04:42 PM
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I want your tablesaw!

LOL!
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post #17 of 17 Old 11-03-2013, 07:27 PM Thread Starter
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which one?

Quote:
Originally Posted by OnealWoodworking View Post
I want your tablesaw!

LOL!

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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