Longworth Chuck

Instructions

1. Start with two pieces of 1/2" x 13" x 13" Baltic birch. 2. Clearly mark the centre of each board with a pencil mark. 3. Secure the first board with double sided tape, add Shaper tape to the field and scan. 4. When placing the image, align the crosshairs at the centre of the SVG file directly over your pencil mark. 5. Start at the bottom of the board and work your way up so as not to cut away any Shaper tape prematurely 6. Use a 1/4" straight bit to make inside cuts for the slots and circles. At zero offset, the slots will be slightly larger than 1/4" so a circular cutting path is required. The circles are used for finger grips when adjusting the chuck. 7. Make all cuts completely through each board (i.e. two passes). 8. Cut out the outer large circle last making an outside cut (or cut out on a bandsaw) 9. Repeat for the second board 10. Install the lathe face plate to one of the boards making sure it is exactly centered. Make sure the screw ends do not poke through the board. 11. Assemble as shown in the photos so that the curved slots on each circular board run opposite to each other. This creates the aperture-like opening and closing motion as the carriage bolts slide in the slots. 12. Install the carriage bolts as shown so that the long slots on the inner face plate board align with a corresponding long slot on the outer board. Do the same for the short slots, using one carriage bolt per slot. 13. Press on the neoprene stoppers, washers and wing nuts. When the wing nuts are loosened a bit, the two boards should slide freely against one another, retracting and expanding the clamping posts. A bit of beeswax and mineral oil in the bolt slots and on the board faces will help the chuck to operate smoothly. With everything fully tightened down, spin the chuck on the lathe (max 600 RPM) to true up the outer rim so that the chuck is completely round and runs true.