15
SPIGOT OPERATION
This is where the jaws contract around a wooden spigot for grip. This function is mainly for box,
goblet and vase turning, that is, end grain items with a fair degree of overhang.
This situation is one of the most difficult to provide secure holding no matter what fixing method is
used.
EXTREME CAUTION WITH THIS OPERATION MUST BE EXERCISED. DO NOT
EXCEED 850 RPM FOR THIS OPERATION. If used properly the Nova chuck however, provides
a very secure grip in this mode.
Instructions below apply to the standard 50mm jaws but the general spigot technique is the same
for other jaw types. However, maximum size of wood blank that can be mounted, maximum
turning speed and recess size varies with different jaw types. Consult accessory jaw instruction
sheet.
With the standard set of 50mm jaws a maximum size wood blank of 100mm (4 inches) diameter
(NOT spigot size) by 150mm (6 inches) length can be turned. Square timber of same length and
between 40mm (1.5 inches) to 50mm and grip all four jaws into wood.
MAKE SURE YOU HAVE AN ADEQUATE GRIP BEFORE OPERATION by vigorously wrenching
the limb mounted on chuck. If any loosening occurs DO NOT PROCEED with operation. Repeat
tightening procedure and retest grip.
SPIGOT SIZE:
Standard jaws will grip a round spigot between 45mm (1 49/64 inches) to 65mm
(2 9/16 inches) approx. Square timber between 40mm (1 37/64 inches) to 50mm square approx.
Jaw slides only: With the 50mm add-on jaws removed, the jaw slides will grip either round or
square timber down to 8mm (5/16 inch). Length limits same for spigot work. Small work not
greater than this diameter can be turned at a speed NOT EXCEEDING 1800 RPM. Larger work
held in the jaw slides should not exceed 850 RPM.
FORMING SPIGOT:
When selecting wood make sure it is sound without splits or weakness -
especially around the area where the spigot is to be formed. REMEMBER WITH FREE END
TURNING, THIS IS THE ONLY AREA GRIP. IF ANY WEAKNESS IS FOUND, DO NOT
PROCEED.
Mount wood between centres and turn the spigot area. Make the spigot as parallel as possible to
maximise the efficiency of the clamping action. Only approximate sizing of the spigot is
necessary, as the jaws will accommodate a wide range of spigot diameters within the spigot limits
stated above. The 50mm standard jaw has a thin lip or shoulder at the front face. This is designed
to bite into the timber as the jaws are tightened. DO NOT CUT A RECESS FOR THE LIP TO FIT
INTO, AS THIS WILL REDUCE GRIPPING POWER.
