1.
Mount your wood blank onto the lathe. This can be done between
centers or mounted in a chuck and held with your live center.
2.
Turn the wood into a cylinder of 5" in diameter or
less.
3.
Using a pencil, first mark the line on the cylinder at the
location that you want the center of your sphere. This is now called the "center
line".
4.
Then make 2 lines to either side of the center line which are
each 1/2 the diameter of your wood blank. These lines are now called the
"diameter lines". Measure the total distance between the diameter lines, it
should be equal to the diameter of your wood blank.
5.
Part down on each side of the diameter lines to create tenons.
These tenons should be 1/2" to 3/4" in diameter.
6.
Cut relief areas to the right and left of the outside lines.
This provides clearance room for the sphere jig to cut without binding or
catching.
Mount Turning Jig
1.
Move lathe banjo / tool rest aside.
2.
Put steel plate on top of the lathe bed.
3.
Put cutter holder arm into post.
4.
Put post through steel plate and screw into clamp while holding
onto the underside of the ways. This will center the jig on your
lathe.
5.
Put the cutter into the holder. Hand tighten down the post and
the cutter. Loose set screw in outer post. Place inner post into outer post with
it's flat facing the set screw in outer post. Place cutter into holder and
tighten down hand screw. Slide inner post up and down until cutting edge is
right on tail center. Tighten down set screw in outer post. You are now set up
to the right cutting height.
6.
Move the jig to a position where when swinging to the left and
to the right, the cutter contact the wood at the edges of the outside diameter
lines equally.
7.
Tighten the post securely.
8.
If you have a 9" or 12" jig, insert and
tighten down each clamp on each side of the center
post.
Turn Sphere
1.
Swing turning jig back and forth to effect the cutting. You can
only take very small cuts(1/16th or less) so
take it little by little cutting down to the tenons at about
1200 RPM.
2.
Sand the sphere and then cut or saw off the tenons just proud of
the sphere.
3.
You can now remount the sphere between cup centers or on a
vacuum chuck. You can now cut off the tenon nubs by using the jig again or using
a turning gouge and some sandpaper.
