Customizable Longworth Chuck for wood lathes:
It is done in OpenSCAD for complete control of variables and the ability to export to DXF for CNC, laser cut, or template making.
v4 - fixed spiral width for bolts (chuck jaws), added animate feature
v3 - added adapter mounting holes
adapterhole=size of hole for adapter
adapterholenum=number of holes - enter 0 for none
adapterholedist=hole distance from center
adapterholeangle=change the rotation of the holes to suit your needs
Variable Explanations (every length is inches):
chuckdia=diameter of the entire longworth chuck
chuckthick=if you are going to CNC/laser, this will help determine thickness of stock
adapterdia=adapter for the chuck to the lathe
offsetedge=distance from the edge to the outer rim of the arc
centerholedia=center hole for axle of chuck
washerthick=if you are using a washer this may come into play
boltdia=bolts size for the chuck jaws
numberarcs=how many spirals or jaws
arcangle=maximum of 90 - adjust this for odd chuckdia
numberholes=number of finger holes
fingerholedia=diameter of the finger hole
fingerrotate=if you need to adjust the finger hole placement coinciding with the number of arcs
res=resolution of arcs and circles
This project was done in 2016.10.30.nightly in order to process the correct rotate_extrude function.
This model can also be built with 3 modules that only have the arcs, include fingerholes, and include a seat for the chuck adapter with fingerholes.
I used the lathe chuck adapter I made on OpenSCAD as well to mount to the lathe itself: http://www.thingiverse.com/thing:1860359
Once you like your design, make sure to File>Export>Export As STL
Create a new OpenSCAD file or open the OpenSCAD DXF Export.scad file and make sure to find the path of your STL. You can use projection to cut a layer and then Export to DXF and open in your favorite CAD or vector program.
File>Export>Export As DXF
Opening your model in a vector drawing program or CAD software
Animated version to show functionality of of chuck
Gluing pieces together with spindle adapter. Nut is embedded within the layers.
Using a threaded nut insert for the piece attached to the adapter. I used epoxy to seal the threaded nut in place. The center hole in this set is slightly larger than the outer pieces of the chuck in order to accept the insert. The bolts attaching the lathe adapter are flat pan head and I countersunk the chuck holes by hand.
Added 2 coats of varnish for protection after sanding...