13
shanks are aligned to the jaw slides and close jaws around it. BEFORE FINAL TIGHTENING
MAKE SURE THAT THE FRONT OF THE BOSS SECTION OF THE SCREW IS SEATED
BEHIND AND AGAINST THE 50mm JAWS. This will prevent any tendency for the boss section
to creep forward when the screw is being used.
The front face of the 50mm jaws has been machined to provide an accurate backing surface. This
is quite an advantage, providing a much tighter fit and better tolerance for irregular face stock.
This feature is also quite an advantage when using the screw to mount a bowl for first stage bowl
turning - forming the outside of the bowl straight onto the jaws (the screw is first removed) after
the recess has been formed.
SCREW DEPTH:
The screw provides 19mm (3/4 inch) of thread beyond the 50mm jaws. With all
wood blocks over 150mm (6 inches) in diameter the full thread depth of 19mm should be used.
Irregular, rough tree blanks (e.g. small sections of tree limbs) not exceeding the above sizes can
be held quite firmly BUT caution must be exercised. Check for adequate contact.
CAPACITY:
DO NOT USE THE SCREW FOR VERY LARGE WOOD BLANKS. Its use is
intended for small bowl and screw chucking work. The maximum capacity which should be
mounted on the screw - 250mm (10 inches) diameter x 100mm (4 inches). DO NOT EXCEED
600 RPM FOR THIS OPERATION. Use tailstock support.
PREPARATION:
The 10.5mm thread requires a drilled hole about 8mm (5/16”) in diameter. The
screw has considerable holding power and it is sometimes difficult to unscrew, so wax or oil the
thread before mounting the wood.
CARE:
The threads are fine and can be damaged by mishandling. DON’T hammer into wood! DO
screw into a pre-drilled hole. Any nicks on the threads can be removed by careful filing.
DOVETAIL OPERATION
Expansion of the jaws into a recess. This function is for bowl and platter turning where the
projection (depth) of the wood blank is not too great i.e. up to 100mm (4 inches).
Characteristically these items have a parallel wood grain. IT MUST NOT BE USED FOR ANY
LONG WORK (OVER 100mm) AS THERE WOULD BE GREAT DANGER OF WOOD TEARING
OUT AND DISLODGING FROM CHUCK.
Instructions below apply to the standard 50mm jaws but the general technique is the same with
other accessory jaws. However the maximum size of wood blank that can be mounted, the
maximum turning speed and recess size varies with the different accessory jaws. Consult specific
instructions included for each jaw set.
This is a strong holding method, using the standard 50mm jaws bowls up to 310mm (12 inches)
in diameter can be turned. DO NOT EXCEED 600RPM WITH THIS OPERATION. OUT OF
BALANCE STOCK MUST BE TURNED AT THE SLOWEST SPEED POSSIBLE.
50mm jaws:
Any recess can be turned bet
ween 50mm (2 inches) and 70mm (23/4” inches)
diameter.
Choose the diameter which suits your bowl design. However, bear in mind that best workholding
will be achieved around 50mm - keep your recesses between 50mm and 60mm where ever
possible. Extra care must be taken while turning with recesses above 60mm. The depth of the
dovetail recess can be varied according to the size and mass of the workpiece. The larger bowl
blanks or softer woods will require a deeper recess up to the maximum of 6mm (1/4 inch).
HOWEVER YOU MUST USE THE MAXIMUM RECESS DEPTH ON ALL RECESSES OVER
64mm (2.5 inches) diameter OR ANY WORK WITH A DIAMETER OVER 150mm (6 inches).
