Trefoil How-to

 Blog entry by BanjoBen posted 04-10-2017 03:20 PM 2063 reads 17 times favorited 9 comments

I posted this project over the weekend and got several questions from people about it, so I thought I’d share some of the process in case anyone’s interested. You can find out more about where the object comes from here: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.314.4240
and here:
https://arxiv.org/abs/0811.0225
Be warned….there’s math in them thar links!

The process is pretty straightforward. To begin, I cut bars 1 inch x 1 inch, making sure they were long enough to get several of the final pieces out, without a lot of waste.

Then I took them over the router table to round over the corners with a 1/4 inch roundover bit.

The next step is to cut the miters. The pieces are needed in two lengths, 5 inches and 7 inches (tip of miter to tip of miter). As with any miters, absolute consistency is key. With 15 miter joints in this contraption, you can’t allow any variation in the lengths, or the angles. I used a stop block to ensure matching lengths

Because of the way the pieces end up having to be arranged, it’s very difficult to clamp this stuff up for gluing. Cutting the slots for the splines helps with this, and using a good thick glue does as well (Titebond No-Run No-Drip is a good choice). But that means the next stage is to match up mitered joints, and cut the slots. To keep track, I labeled all of my pieces from A to O, with an arrow to indicate the orientation. That way, I could match up the slots later.

The jig above is a simple, homemade version of a spline jig that many of you probably already have. Someday I’ll make a better one, but it got the job done.

At this point, the only thing left is to cut the splines themselves, and glue things up.

My process was to glue up pairs (matching corresponding letters in sequence. The Titebond No-Run glue works pretty well with hand pressure for 30 seconds or so, and then give it time to set. You can see the bottle of Titebond3 in this picture. I did use it for a couple of joints on this, and quickly learned my lesson…

Once you get pairs glued, up then match those up, until at the end you have two pieces that can be glued up to the final form. After trimming/sanding the splines, you can finish with your choice. I used Enduro-Var from General Finishes.