In my last video I turned a segmented bracelet using my new home made bracelet chuck. It is an expansion chuck using basic engineering principles with lathe components. It uses 2 tapered end plugs, 8 tapered side slats, 2 automotive band clamps, 4 latex tubing rings, and a little duct tape.
One end plug is fitted to the lathe spindle. As originally designed, I would have drilled a hole in the plug sized to a spur drive center. However, I decided to thread it to hold it more firmly in place. This is escpecially nice when assembling a bracelet onto the chuck. I used a tap that matches my lathe spindle from Beall.
The other end plug is fitted to the lathe's revolving center. Again I decided to tap it to match. This time I used a carbon steel tap set from McMaster Carr (Price $27). Carbon steel should be good enough for the number of times I'll use this tap especially in wood.
The slats are out of straight grained wood, in my case Baltic birch, 10" long by 1.25" wide and 5/8" thick. I cut a taper from the middle of the 10" side to 1/4" from the other side. One slat was my template for turning the tapered end plugs. After turning the end plugs, I ripped the slats to 1" wide and sanded a taper on the opposite sides. (4 tapers: 2 sawed - 2 sanded)
The chuck works by the lathe tail stock forcing the tapered ends together. This expands the side slats until they are constrained by the bracelet to hold it in place.
Theoretically, the bracelet could be the only thing holding the slats in place.
Practically, however, and with safety in mind, band clamps are also used in case the bracelet breaks. If that were to happen without the band clamps, parts and pieces could fly all over and possibly injure someone.
With metal bands now on the slats, they should not explode but now the band clamps pose a hazard. They have bumps where the screw mechanism is and a trailing band of metal. To counter this risk, the slats are 10 inches wide (otherwise, they could be shorter), the band clamp is always positioned so the trailing band trails opposite the rotation of the lathe (so it cannot dig in to a hand), and latex rings provide a final layer of protection. A piece of duct tape also holds down the trailing part of the band clamp.
The latex rings are cut from standard latex tubing. The ends are glue together on a short piece of wood dowel with medium CA glue.
This chuck avoided having to flip the bracelet from side to side and having to fit it to a jamb chuck to finish the outside of a bracelet. It made my turning job much easier and with better results.
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