(1) Laying out and marking the bead sections.
(2) Drilling for the lathe center.
(3) Lining up the first cut on the end of a rod. The mark for the next bead is lined up with the face of the chuck jaws.
(4) First cut complete.
(5) Second cut complete.
(6)"String of pearls" supported by a live center.
(7) Boring the first beads.
(8) Parting the bead from the string.
(9) Countersinking bore.
At the start of Pangur Ban's construction, I decided I'd make as many of her components myself as was possible. Parrel beads are cheap and easy to find. But, I had a lathe and some time, so why not make my own?
I purchased a three-foot piece of 1 inch diameter Delrin rod. With that as a starting point I could decide what length and end radius would work. From that I could grind a forming tool that would cut the face of one bead and the rear of the next at one time. (see photo 3) With the tool made, parrel beads can be made in quantity.
A permanent Sharpie marker is used to divide the rod into bead length segments. (1) The marked rod is chucked in the lathe, and it is drilled for a lathe center. (2) This must be done very close to the chuck, as Delrin is pretty flexible.
The rod is advanced in the chuck until the first mark lines up with the face of the chuck jaws. The forming tool is lined up with the end of the rod. (3) Make the first cut. (4)
Advance the rod till the next mark lines up with the face of the chuck jaws. Advance the forming tool to make the second cut. (5) Repeat this advance and cut process. After four or five beads are roughed out, the end of the rod will have to be supported by a center in the lathe tailstock. (6)
When the rod has been turned into a "string of pearls", it is drawn back into the lathe headstock. The center is replaced with a drill chuck, and the rod is bored. (7) With my drill, I can drill a little more than two beads at a time. It is important to drill the beads while the rod is completely supported by the chuck jaws, otherwise the drill will wander off center.
Advance the rod until about one and a half beads protrude past the chuck jaws. Mount a parting tool, and cut off the bead. (8) Repeat until all the beads are parted.
As a final step I mounted a countersink in the lathe chuck, and used it to bevel the edges of the hole bored in the beads. (9) You can see from the photograph that the beads will frequently part with a thin flashing around one end of the bore. This is caused by the flexibility of the plastic. This flash can be removed at the same time as the countersinking operation.
All images and text Copyright Dale Austin, 1962-2008