How would you join these?

[davidtu]

<< newbie alert!

Attached, please take a look at the base of a school project that I was helping LOML with and pretty much failed at miserably. The task: connect the 3 4x4 douglas fir blocks at odd angles (angle A <> angle B) both are obtuse... say 122 degrees and 110 degrees for fun.

This had to be strong enough basically to support its own weight. We weren't confident that glue alone would suffice so I went ahead and tried to do dowels. I screwed it up b/c I forgot to make the dowels perpendicular to the joint face rather than the sides of a given block--I actually knew better but by the time I had things setup I forgot! Duh.

In any case, it was an incredibly hokey setup using clamps on clamps on clamps and ultimately by eye--using a 12" drill press. The press rotated to hang off the table's edge but the pieces were too big to fit on the drill work table or even the table the press sits on... I was just 1/2" spade bit drill.

SO... what was the correct way to make the connection AND how would you build the jig to do it?

You have at your disposal: Table saw, Miter saw, 5.5" circular saw, 12" drill press, Mortiser, Router, Finish and brad nailer, laser and other levels, assorted hand power tools. All the clamps you want.

Thanks!

[gary]

Do you have a tenoning jig and dado blade available for your table saw? You could try to place one or two large splines in each joint. It would be very strong safe to make.

[LCHIEN]

End-grain to end-grain glue joints would be terribly weak.
My advise would be one of these:

1) A half lap joint - compared to a half lap joint for joining two ends at 180 degrees, there are a couple of problems - there will be something sticking out on the outside of the angle and a gap on the inside. Sawing off the overhanging piece (like with a bandsaw) will be very close to being a filler for the gap on the inside of the "curve" less the kerf. Glue along the face and screw for added strength.

2) A half lap joint with a connecting plate. In this the half lap cut is on the same side (top) and you span the laps with a V-shaped (plywood) plate to fit. Screw thru the V-plate for strength.

3) If appearance is primary then put a loose tenon into mortices driven into the ends. This will require some fixturing on your mortiser to get the correct angles (perpendicular to the faces) and I'm not really sure how well a mortiser works into end grain. (might be surprisingly easy if it does not try to follow the grain.)

[Tom Miller]

How rough can you go with the joinery? If we're talking "quick and dirty", you might consider cutting the angles with the miter saw, and then drilling for lag bolts through the edge grain of one piece and into the end grain of the other.

Drill a hole for the bolt head and washer to hide in first with a large spade bit. Then drill for the shank with a smaller bit.

Use a polyurethane glue prior to keep the pieces from swiveling.

Regards,
Tom

[Boomer_01]

Try another approach

I don’t know your application but have you considered making the piece as a unit rather than from three individual pieces. You could face glue layers of plywood, MDF, or some other acceptable sheet goods to the desired thickness. Construct a template from scrap that lays out the proper angles and footprints of the final piece. Use the template as a marking guide and cut the piece as a single unit on a band saw.

You might have some clean up (saw marks) depending on just how perfect the edge needs to be and the angles may not be perfectly crisp, but you would have a very strong unit when complete.

Like I said the aesthetics may not be acceptable but it is an option you could consider.



Boomer

[Scottydont]

Is the interior of those peices hidden? If so you could make blocks to go on the inside, glue and screwed. If not I would use spline joints or biscuits.

[crokett]

I'd do half laps or laminate sheet goods to required thickness and cut the piece as a single piece.

[jackellis]

How about splines?

[Warren]

Not knowing the end use, for strength I'd mortise and tenon with two through holes for pegs at each joint. You would want to bevel the inside of the joint and the ends of the mating boards. (It's late and I'm starting to get confused . . . I'll try and muddle through though.) The holes for the male part should be a hair off the long axis so as to draw the pieces together when the peg is driven home. A little glue on the mating faces and you should have a strong joint. Knock the protrusions off and you should be good to go.

Mind yourself now, this advise is worth only what you paid for it.

[dwitzke]

You could cut angled mortise and tenons. Layout the joint then cut with your hand chisels. No power tools required.

You could also try pocket screws.

[Russianwolf]

[QUOTE=LCHIEN]End-grain to end-grain glue joints would be terribly weak.
My advise would be one of these:

1) A half lap joint - compared to a half lap joint for joining two ends at 180 degrees, there are a couple of problems - there will be something sticking out on the outside of the angle and a gap on the inside. Sawing off the overhanging piece (like with a bandsaw) will be very close to being a filler for the gap on the inside of the "curve" less the kerf. Glue along the face and screw for added strength.

QUOTE]
Why not just cut an angled halflap? No need to cut off peices or having a gap. Takes alittle planning but not hard to do. Given that these are 4x4, you can do it with a handsaw. Or cut the shoulder with a circular saw and the bandsaw for the other cut, and cleanup with a chisel. Then add a couple dowels through the halflap and bingo, she won't be moving anytime soon.

[davidtu]

Thanks to all of you for a bunch of excellent suggestions!

To satisfy any lingering curiosity, the unit had to be made from a nice piece of wood, for appearances.... we used a pretty clear piece of douglas fir, so MDF would not work in this case. Also, we did care about hiding the connections as much as possible, though it would have been acceptable to have something show on the inside angles.

Seems like the half lap joint may have been the easiest (for me) solution to have used.

Best regards to all for your insights!