Descending Ashtray

I spent most of today working on this case for the Labyrinth game. It’s really starting to take (enormous) shape. This box housing the game board and golf ball diverting mechanism is 32 inches tall, 57 inches long and 47.5 inches wide. Pretty big!

I also began work on the two oversized knobs which will control the x/y tilting mechanisms. Here’s how I did it, and it’s also a good explanation of how to cut perfect parts of the same size/shape, again and again and again …

I began by using one of my router-based circle cutting jigs to cut a 7.5-inch diameter circle template from 3/8 in. MDF.

Once that was done, I screwed the template to a blank of 3/4-inch thick particle board, 8-inches square. The idea is to form these into 7.5-inch diameter circles, and glue 3-4 circles together to create one 3.75-inch thick piece, creating a scale knob for the game.

I used the bandsaw to trim the blank to rough size, following the template as a guide. It’s important NOT to cut the template, since that will cause future blanks to receive the same error. I try to get as close as possible, but maintain about a 1/8- to 3/16-inch margin for error. The idea is to use the bandsaw for most of the waste removal, and sweeten the shape with the router in the next step.

With a pattern-cutting bit mounted in the router table, it’s time to cut the blank to final shape. A bearing on the bit at the same height as the table surface follows the contour of the template. Above the bearing are two cutting blades, or “flutes.” The flutes are the same diameter as the bearing, and allow you to perfectly machine the blank’s shape to the template’s. I’m using a bottom-bearing pattern bit, but another version is available with a bearing at the top (used often for trimming laminate to match a countertop’s final edge). You can see from the photo that this process produces quite a bit of dust. Many router tables have some kind of dust collection system, but I’ve not gotten to that yet. It’s always a good idea to wear a mask when doing this anyway, as it does produce a lot of fine dust that wouldn’t be great for your lungs.

Once the routing is done, all that remains is to remove the template from the finished blank.

I produced 9 or ten identical circles in about half an hour, most of which was spent setting up the router jig and changing the bit in the table-mounted router. This method also works well for any odd-shaped piece which you’d like in multiples, and is used commonly in production furniture making. Smaller diameter bits can capture more detail in the blank, but can’t remove material as quickly. I’m using a 1/2-inch diameter bit here.