Set of five small rings

(Originally posted on October 28, 2009)


These were also inspired by discarded designer samples -- in this case, of Abet Laminati Tefor recycled thermoplastic, which looks something like this: http://bit.ly/3mCul2.

...except that these samples had 1/4 inch holes punched in each corner so that they could be strung on a chain. I measured 7/8 inch in from each face and marked out four square blanks with one rounded corner. I stacked the samples and duct-taped around their edges, then gang-cut them on the bandsaw. (Duct tape was my choice here for the fabric backing, which stretched to apply light pressure to hold the stack aligned. But I also like the cred.)

I then marked centre and drilled a 1/4 inch hole in each blank, stacked them all up on a 1/4 x 20 bolt, and added a pair of counter-tightened nuts. This provided a shaft that I could mount in a Jacobs chuck on the lathe. Turning the rings round was more fun than you’d think -- long, thin spirals of coloured plastic off a shallow-fluted detail gouge. I lightly sanded the rings on the lathe, and then removed them from the bolt.I shattered a couple of workpieces trying to find a way to open up the central holes. I expected to be able to enlarge them using a succession of twist drills, but no matter the speed or feed rate, I couldn’t make it work. And with only about 1/8 inch thickness outside the intended 5/8 inch bore, I couldn’t see how to clamp the rings to attempt a hole saw.When all else fails, try abrasives, and a conical grinding point in the drill press worked, if not well, then eventually. I was able to hold the rings by hand while reaming them out. By inspecting the progress frequently and selectively applying light pressure, I kept the bore roughly centered.

I then mounted a 1/2 inch sanding drum with a medium-fine grit (probably about 220), cleaned up the bores, and cut a slight bevel at the inside edges for comfort. The outside edges were no longer quite concentric in some cases, so those were reshaped very gingerly on a benchtop belt sander. I then hand-sanded the rings with 220 grit, and finished by burnishing the plastic with my fingernail.

The finish I ended up with feels good, but looks rough. I’ve been experimenting with the offcuts from this project, and the solution seems to be to finish with scraping and burnishing after the final abrasive shaping.

But Eve wants them for herself, so I must have done something right.