Multi-lap joints with the quick-set tenon jig
I couldn't find a good name for this type of joint. It's like a box joint, but it's for pieces oriented more like in a lap joint or bridle joint. "Multi-bridle joint" sounds silly, so I'll call it a multi-lap joint.
The quick-set tenon jig already has two stops for alternating between two cut positions with the flip of a lever. But by adding a template to the front, many more stops positions can be obtained, Here I'm adding a "blank" for a new template.
The set-up begins with the face of the jig against the saw blade, and the dial indicator adjusted so that it reads zero.
I'm making a template for cutting a joint with 1/4" (6.35 mm) wide fingers. The first slot goes from the edge to 1/4". The blade itself already cuts away 0.100", so I only need to move the jig over by 0.150", plus another 0.003" to give the joint some slack.
I then move the jig to 0.500" from the starting point (move by 0.250 finger width plus 0.100 blade thickness), I again punch this location, then move by 0.250 + 0.003, repeating the above steps for each slot I need to cut.
The dial indicator only has 1" (25 mm) of range, so after 1" of movement, I move the dial indicator's reference point by exactly 1" (using the dial indicator to check) to get another inch of range. You can get dial indicators with more range, but for most things, the one I have is enough.
I need to cut slots between the edges of the punch marks. The easiest way to do that is on my table saw, using my small table saw sled
It's much easier to position the workpiece with the marks facing up, cutting the slots on the bottom side of the template.
I then put the template back on the jig. With the jig face touching the blade again, I use a cut off bolt (the thread-less part), inserted into the hole in the lever, to line up the template so the start of the first notch is where the jig is now.
I push the handle to the left until the bolt hits the left side of the first slot, make a cut, then push the handle right until the bolt hits the other side of the slot, make a cut there, and then make a third cut between those two to clean out the rest of the slot.
To move to the next slot, I lift the bolt and move the lever over the next notch, letting it drop into that notch, and repeat.
To cut the mating part, I need to move the template so that all the notches are offset by 1/4". So I start with the face of the jig touching the blade again, move it over by 0.250", then loosen the template and line it up with the bolt in the handle so that a notch starts where the jig is now.
I also used this type of joint for the angle brackets that hold up the outfeed table of my table saw.
So next time I need to make a template, I can just triple the size that I need and cut that straight out without setting it up on the jig.
This because the control lever gives exactly a 1/3 reduction from where the bolt is (top circle) to the pivot point on the carriage (middle circle), so long as the fulcrum (bottom circle) doesn't move side-to-side. The fulcrum does move slightly because the middle pivot is fixed to the sled, so it has to move in a straight line. This means the fulcrum on the back has to move forward and back just slightly as the lever rotates. That's what the link on the back is for. And as long as that link doesn't pivot too far, it causes only negligible side-to-side movement of the fulcrum (< 0.0005" or 0.01mm).
Precision can be very satisfying.
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