120 degree joinery

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Forum topic by kaloosick posted 05-30-2013 04:49 AM 3751 views 0 times favorited 6 replies Add to Favorites Watch
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6 posts in 2069 days

05-30-2013 04:49 AM

Hi all, I’m starting on a coat rack that requires the joining of 3 pieces that are oriented vertically against each other with 120 degrees of separation (think a 3 pronged crosshair, I don’t know if there is a better term to describe this). Similar to this design

My question is how does one go about making this joint. My material is 3/4” ply, and my ideas on this problem have only gone as far as mitering the faces to be joined, any better thoughts or hardware solutions?

On the page I linked they are utilizing some sort of slotting and locking mechanism to make the joint, does anyone know what these are actually called and if they are available?

6 replies so far

View AandCstyle's profile


3185 posts in 2497 days

#1 posted 05-31-2013 12:23 AM

Traditionally, this would be done by making sliding dovetails in a cylinder. Look at this table. HTH

-- Art

View bondogaposis's profile


5153 posts in 2591 days

#2 posted 05-31-2013 12:35 AM

Just glue it up.

-- Bondo Gaposis

View Buckethead's profile


3194 posts in 2108 days

#3 posted 05-31-2013 01:00 AM

Double mitered and glued seems sufficient but I think a spline or three could look attractive. You could create splines which match the profile or you could use circular hardwood discs as splines that create shadowlines at the core. If you wish to duplicate it exactly though… I agree with bondo.

-- Support woodworking hand models. Buy me a sawstop.

View Buckethead's profile


3194 posts in 2108 days

#4 posted 05-31-2013 01:09 AM

Just thought of another option… Think tinker toys. A small wheel/disk (with a radius small enough that it would fit inside the profile) with holes drilled to receive dowels. A triangle would actually be easier. Just rotate an isosceles triangle disk 90 degrees and each surface would then be perpendicular to the plywood. Each edge of the triangle would need to be a hair shy of 3/4” to remain invisible… Which doesn’t leave much volume for dowelling. So…. Never mind…... :-)

Still, if used as visible splines, these could work. Anyway.. Thanks for getting me to think!

-- Support woodworking hand models. Buy me a sawstop.

View casual1carpenter's profile


354 posts in 2715 days

#5 posted 05-31-2013 02:43 AM

I see buckethead’s point and if one part could

be cut with 30 deg each side to give a 60 deg included angle, sort of looking like the point of a pencil when looking from the end. the other pieces cut at 90 deg could join up with your favorite method. big arguments there, dowels, biscuits, t&g, splines, glue, or even heaven forgive, pocket screws. not that i have overly lots of issues with pocket screws mind you, but i do feel that you could be looking at a serious precision cutting and joining project for a one off. it would be good to know your style of woodworking, abilities and tooling and just how much effort you wanted to put into the project.

I truly hope this post communicates my thoughts, I’ve been into my cups tonight, so my thoughts might be a slight bit fermented. I did follow your link and the orig guy did three identical parts which is cool but offers a small pcs to pcs glue surface and not much ability to use a mechanical helper such as a dowel or (insert your preference of list here). BTW, just how much is 89 L things in US dollars?

View firefighterontheside's profile


19623 posts in 2096 days

#6 posted 05-31-2013 03:05 AM

Can you do this? A lot of glue surface and you could use biscuits.

-- Bill M. "People change, walnut doesn't" by Gene.

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