Sherline 5000 Mill Assembly Instructions
-28-
3-JAW CHUCK OPERATION AND MAINTENANCE
FIGURE 45—Jaw locations and identification
FIGURE 46—Reversing the chuck jaws.
NOTE: Always start with position “A.”
JAW LOCATION
STANDARD JAW
IDENTIFICATION
REVERSED JAW
IDENTIFICATION
1ST
1ST
1ST
1ST
2ND
2ND
2ND
2ND
3RD
3RD
3RD
3RD
A
A
B
B
C
C
JAW LOCATION
The 3-jaw self-centering chuck is the most popular of all
the accessories available for the Sherline lathe. It is
available in both 2-1/2" diameter (P/N 1041) and 3-1/8"
diameter (P/N 1040). These chucks will grip round or
hexagonal work quickly, since the jaws move
simultaneously to automatically center the work being held.
The jaws on the chuck are designed so that the same chuck
can be used for both internal and external gripping. Jaws
are reversible for holding larger diameter work. Due to
the nature of the design of a 3-jaw chuck, it cannot be
expected to run perfectly true. Even 3-jaw chucks costing
five times more than the one made for this lathe will have
.002" to .003" runout. If perfect accuracy is desired in a
particular operation, the use of a 4-jaw chuck is
recommended. Each jaw is adjusted independently so parts
can be centered with total precision. Both a 2-1/2" and
3-1/8" 4-jaw chuck are available for the Sherline lathe as
P/N 1044 and P/N 1030 respectively.
NOTE: DO NOT TURN THE LATHE SPINDLE
ON WITHOUT HAVING THE CHUCK
TIGHTENED. The acceleration of the spindle can
cause the scroll to open the chuck jaws if not tightened!
The 2-1/2" 3-jaw chuck (P/N 1041) is designed to take up
to 1-3/16" (30 mm) diameter stock with the jaws in the
normal position. The 3-1/8" 3-jaw chuck (P/N 1040) is
designed to take up to 1-1/2" (38 mm) diameter stock. For
larger diameter work, reverse the jaws (See Fig. 46). To
prevent permanent damage, finished, turned or drawn stock
should only be held with this chuck. For rough castings,
etc., use a 4-jaw chuck.
DO NOT OVERTIGHTEN THE CHUCK.
Use only moderate pressure with the spindle bars
(P/N 40580) supplied.
To reverse the chuck jaws, rotate the knurled scroll until
the jaws can be removed from the chuck body. After the
jaws are removed, they can be easily identified by the
location of the teeth in relation to the end of the jaws (See
Figures 45 and 46). To maintain chuck accuracy, the 2nd
jaw must always be inserted in the same slot even when
the jaws are reversed. This slot is identified by the laser
engraved letter “B” next to the slot. Always insert the jaws
in the order and location shown on the drawings. Turn the
scroll counterclockwise when viewed from the face of the
chuck until the outside start of the scroll thread is just ready
to pass the slot for the first jaw. Slide the first jaw as far as
possible into the slot. Turn the scroll until the first jaw is
engaged.
Due to the close tolerances between the slot and jaw, the
most difficult part in replacing the jaws is engaging the
scroll thread and first jaw tooth without binding. Therefore,
never use force when replacing the jaws, and, if binding
occurs, back up the scroll slightly and wiggle the jaw until
it is free to move in the slot. Advance the scroll and repeat
for the second and third jaws. The scroll thread must engage
the first tooth in the first, second and third jaws in order.
REMOVING A CHUCK FROM THE SPINDLE
Use one tommy bar in the hole in the spindle and another
tommy bar in a hole in the chuck body to achieve enough
leverage to unscrew the chuck (counterclockwise) from the
spindle thread. If the chuck becomes stuck on the spindle
thread, put a tommy bar in the hole in the chuck body. Place
a block of wood against the tommy bar where it enters the
chuck. With a small mallet, give the block of wood a sharp
tap, turning the chuck in a counterclockwise direction. It
should not be necessary to hold the spindle, as its inertia
should be sufficient. (Don't hit the tommy bar anywhere
other than right where it enters the chuck or you could bend
it.) This small but sharp force at the outer edge of the chuck
should break the thread loose and the chuck can then be
unscrewed using the tommy bars.