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March 18, 2006

brass "open hole double ball" joint

by sven at 10:43 pm

Very exciting! I just this afternoon created my first really successful "open hole double ball" joint!

side view

This design was inspired by Lionel Ivan Orozco's tutorial on how to make an open hole double ball joint and by a link off LIO's site that describes a similar design made of brass. It's a lot like a "ball and socket" joint -- but the balls just sit on top of the holes, rather than being recessed into sockets.

I'm scheming to make a full puppet armature out of these joints. Expect to be hearing more about them... ;-)

top view

If all goes well with these joints, I'll probably do a full write up about how to make them. In the meantime, here are a few details...

The balls are 8mm hollow brass beads that I found at a bead store. The brass rod and the brass bar (for the sandwich plates) are K&S brand materials. The rod is 1/8" diameter. The bar is 1/4" wide and .064" thick; I cut it to be 18mm long using a Dremel cut-off wheel. Beads are measured in millimeters -- which led to this weird combination of metric and English units.

The trick to making the sandwich plates was to screw them together before drilling the holes that seat the beads. The screw is 4-40 and 1/2" long; it has a cap that can be turned with a hex key. I threaded the middle hole myself, using a tap. To allow the plates to move correctly, only one side of the sandwich gets tapped. After all the holes were drilled, I rounded off the bar's corners using the Dremel again.

I used a power drill to enlarge the hole through the bead. Because the bead is hollow, I was able to snip off a little bit of solder and actually put it inside the bead with the rod. I heated the bead with a butane micro torch (actually my brulee torch!) to melt the solder and seal the bead in place. I didn't round the end of the rod that pokes out of the hole -- but the joint seems to work very well, nonetheless.

posted by sven | March 18, 2006 10:43 PM | categories: stopmo