Longworth Chucks are quite handy for woodturners – they make cleaning up and sanding the bottom of your bowls very easy.
The trickiest part of this jig is cutting the arcs. If you were a geometry whiz, you could lay out the arc pattern yourself, but we’ve helped you bypass all of that math by offering a paper pattern that can easily be glued to your stock. Download the 12-inch diameter Longworth Chuck Routing Pattern here or the 16-inch diameter Pattern here.
If you’ve got a CNC setup available to you, we’ve provided files for 10″, 12″, 14″, 16″ and 20″ chucks. You’ll want to do some testing to make sure the settings are consistent with your individual setup, especially for the diameter of faceplate that you’re using.
All sizes use a 1/4″ straight bit and the origin is at the center of the workpiece. Make sure you use a die-board under your workpiece.
The 10-inch diameter CNC files utilize 11-1/2″ x 11-1/2″ x 3/4″ workpieces.
The 12-inch diameter CNC files utilize 13″ x 13″ x 3/4″ workpieces.
The 14-inch diameter CNC files utilize 15-1/2″ x 15-1/2″ x 3/4″ workpieces.
The 16-inch diameter CNC files utilize 17-1/2″ x 17-1/2″ x 3/4″ workpieces.
The 20-inch diameter CNC files utilize 21-1/2″ x 21-1/2″ x 3/4″ workpieces.