Hi! I'm trying to figure out how to join two planks together at an angle. Basically it's a piece of a jig. It's somewhat hard to describe the end result so I've drawn a sketch. The joined part will bear stress from a moderate load, let's say about 5-7 lbs of weight. So what kind of joint should it be? I guess either a butt joint of some sort or a finger joint. Thanks for help!
IMO...Solid wood is most defiantly the way to go.
I would stay away from plywood for this joint union. The cross graining of ply is too weak for "scarf joints" which this would be...since a "butt joint" is the most simplistic "scarf joint" form. If you go with something thicker than 1", like even 1.5" it would become much stronger, as you will have more "meat" to work with giving you a much stronger joint.
There are a number of scarf joints that would work here well. The "Finger splice" (already offered) would render a very strong joint, yet can be a bit of a challenge to cut in such a 150° angle configuration. Some of the simpler "Splayed Scarf" joint would also work as well, and a "Pegged Scarf" with doweling (~3/8" dowel?) may well be more than you need if well glued to meet your 7 lb strength range of load capacity.
This is a really easy scarf to cut actually, and I have used it in everything from "thread grafting" in Penzai, to "down and dirty" fast splicing for just such applications as yours.
First, just create the geometry you want. Glue it up well and let set overnight!! Then simply drill by eye so that you get into the foundation piece at least 2" in. The angle of this drilled hole is not critical...straight "by eye" is level enough. Then simply glue and drive in your dowel/trunnel let set again overnight and trim off the dowel.
P.S. The next simplest is a "scissor" or "strokes bill" scarf...If the dowel method is not appealing...We use these all the time as well for full structural unions in rafters and major beams...