Instruction/Data Sheet
Page 6
Place the toolrest at the “safe toolrest position”
Turn the outside diameter of the bowl blank so that it is perfectly round.
Now place the toolrest in the “safe toolrest position” at the face of the blank and true up.
Mark the centre with a pencil.
Undo the eccentric boss screws and rotate it so that ‘35’ is visible in the sight window.
Retighten the screws and transfer a mark at position “I” onto the main chuck body for the reference
point for the rest of the marking out.
Move the toolrest to a new “safe toolrest position” as the wood is now considerably off-centre.
Reduce the lathe speed as slow as possible and switch on. Take a minute to
watch the wood spinning to get an idea of how it looks when it is spinning this far
off-centre. Increase to a safe speed where the lathe is running without any vibration.
Mark a new centre number ‘1’.
Loosen the screws and remove the eccentric boss.
Undo and remove the machine screw & washer and very carefully remove the faceplate from the
bi-hexagonal locating socket and turn it through 120 degrees, which is 4 positions in the socket.
Replace it back into the socket and re-tighten the machine screw and washer.
Replace the eccentric boss back into the main body.
Set to position ‘35’ in the sight window and re-tighten the boss screws.
Now the line marking ‘2’ will be in line with the reference mark on the chuck body.
Move the toolrest to the “safe toolrest position” at the face of the blank.
Switch on the lathe and mark a new centre No. ‘2’.
Switch off the lathe and loosen the boss screws to remove the eccentric boss.
Undo and remove the machine screw & washer and very carefully remove the faceplate from the
bi-hexagonal locating socket and turn it through 120 degrees.
Replace it back into the socket and re-tighten the machine screw and washer.
Replace the eccentric boss back into the main body, set to position ‘35’ in the sight window and
re-tighten the screws.
Now the line marked ‘3’ will be in line with the reference mark on the chuck body.
Move the toolrest to the “safe toolrest position” at the face of the wood.
Switch on the lathe and mark a new centre No. ‘3’.
You will now have 4 centres marked on the face, one true centre and three offset centres.
Next mark an arc using compasses from each offset centre to just inside the outer diameter of the
bowl blank. These marks will give a guide to the outside shape and size of the finished 3-sided bowl.
Robert Sorby
Instruction/Data Sheet
ECCENTRIC CHUCK PROJECTS
