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I'm making half-lap joints in 2x4, but they're not at a 90° angle. Therefore, I need two jigs, one angled 10° from square in each direction.

Due to poor planning on my part, I made one jig out of one piece of 1/4" plywood with some blocks screwed to it to locate it on the 2x4, and the other jig I made out of two pieces of 1/4" plywood. Obviously (though it took 2 days of working on this before it finally hit me), that is the reason my dado cuts are coming out different depths.

If my dados are different depths, it that going to cause any strength issues in the final, assembled project?

I can, if necessary, reset router depth and go recut all the ones on the doubled 1/4" template, but I really don't want to unless I have to (either for strength or to make the pieces end up flush, as I'd like them).

This is what the assembled pieces will look like. This is a test piece that is simply screwed together. While screws will likely be sufficient, it will be relying entirely on the sheer strength of the screws like this, so I figured a half-lap would be stronger. Also, since this a piece of shop furniture, it's an opportunity to learn a new skill and if it doesn't come out perfect & beautiful, it's still a learning experience that will produce something functional for the shop.

Lumber rack frame

(Note, there will be locking casters under this so it will be mobile - I, sadly, don't have enough space to let it sit in the middle of the room.)

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    Seems like a given that if one member is cut thinner it won't be as strong. The question is: will it be strong enough? And that just begs the question: Strong enough for what?
    – Caleb
    Commented Oct 4, 2021 at 21:35
  • Also: Why do you need two different templates? Can't you just turn one around? A photo might help us understand what you're talking about.
    – Caleb
    Commented Oct 4, 2021 at 21:38
  • I'm making an A frame, @Caleb with horizontal cross members. The uprights are leaned toward each other at 80°, so the dados on one side are at 80° from vertical while those on the other side are 110° from vertical. Instead of adjusting the alignment guide blocks back and forth by 20°, I just made 2 templates.
    – FreeMan
    Commented Oct 4, 2021 at 22:16
  • Strong enough for "what" is for a lumber/sheet goods storage rack. I'll have sheet goods on one side (stored on the 8' edge), long lumber down the middle of the A frame, and shelves on the other side for shorter pieces.
    – FreeMan
    Commented Oct 4, 2021 at 22:18
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    Loos 10x better than my shop....
    – gnicko
    Commented Oct 9, 2021 at 23:55

1 Answer 1

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If my dados are different depths, it that going to cause any strength issues in the final, assembled project?

Obviously there's a certain amount of personal interpretation on this, but I can't imagine how this wouldn't be totally fine.

When doing half-laps AKA halving joints spreading the load equally between two crossing pieces of equal thickness, by taking half off each, is obviously the textbook application. But, there are many similar joints — lap joints of one type or another — where only one part is dadoed (for various reasons) and anything extra is better than this because it adds the second set of shoulders.

I think it's also worth pointing out that the quickest and dirtiest version of what you're building would simply use overlap joints so there'd be no joinery at all. And I bet that could yield something that will give longer service than one might guess, especially if glued.

So just in case it needs to be said, glue is advisable as well as the fasteners. However if you want this to remain disassembleable because somewhere down the line you'd like to be able to re-use some of the wood, then dovetail the screws and/or use at least three per joint.

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  • To be honest, the sample in the picture is made out of 25+ year old lumber that came from the old rack I'd built. It made very inefficient use of space and was hard to get things in & out of, and mostly became a place where "stuff" was piled. That rack was held together by 3 drywall screws per joint. TBH, I'm really not worried about strength (though there will be added stress when this rolls), I'm just working on improving my joinery skills before moving on to more critical things.
    – FreeMan
    Commented Oct 4, 2021 at 23:24
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    "I'm just working on improving my joinery skills before moving on to more critical things." +10. I do the same thing, the first halving joint I did was for the 90° corner on a bench hook, when just a butt joint would have been perfectly suitable. In the same vein when restoring old tools I practice French polishing and a full high-gloss varnish finish... even on lowly stuff like file handles LOL
    – Graphus
    Commented Oct 5, 2021 at 0:09
  • I wonder if this is a case where the ad hoc rules about sizing mortises and tenons might apply. Like, I'm not sure the lap joints have to be exactly "half" in all cases, but a "no larger than 1/x" rule-of-thumb might apply here. Though, I suppose, no greater than half is the first such rule.
    – user5572
    Commented Oct 5, 2021 at 13:17

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