Grizzly G0709 - Manual (Page 67)

Model G0709 (Mfg. Since 5/11)
-65-
Shear pin
Replacement
A straight 4 x 42mm brass shear pin ( figure 105)
holds the leadscrew and the drive hub together.
the pin is designed to shear and help protect
the lathe drivetrain from damage if an overload is
encountered.
Tools Needed Qty
hammer ............................................................. 1
dowel punch
3 ⁄
16
" ............................................... 1
drill Bit 1 ⁄
8
" ......................................................... 1
hand drill .......................................................... 1
Wood screw #8 x 1" (or longer) ........................ 1
pointed Center punch ....................................... 1
standard pliers .................................................. 1
To replace the shear pin:
1. disConneCt lAthe FroM poWer!
2. unlock the half-nut lever and disengage the
gearbox so the leadscrew can be rotated by
hand.
3. rotate the drive hub, and inspect it to see if
the pin is still stuck in both sides of it.
—if one half of the shear pin has fallen out
and the leadscrew shaft can be seen
through the pin hole, rotate the leadscrew
and until the end of the inner sheared pin
can be seen. next, insert the
3 ⁄
16
" dowel
punch into the hole and tap the pin out
through the other side.
—if the shear pin halves are still stuck in both
sides of the drive hub, center punch one of
pins and drill an
1 ⁄
8
" hole in the pin approxi-
mately 1 ⁄
4
" deep. next, thread the #8 wood
screw into the hole until the screw begins
to thread into the brass. using pliers, pull
the pin from the hole, and drive the rest of
the pin out as outlined above.
4. Align the holes in the drive hub with the hole
in the leadscrew, and tap the new shear pin
into position until it is flush.
Tip: For easy shear pin replacement in the
future, use the center punch or a scribe and
mark the end of the drive hub and the side of
the leadscrew with a timing mark to indicate
where true hole alignment is located. Next,
scribe a line on the leadscrew just where it
enters the drive hub, this line will indicate cor-
rect depth of leadscrew. Should the pin ever
shear again, line-up the marks, and drive out
the pin pieces, and tap in the new pin.
figure 105. leadscrew shear pin.
For example, the pin may shear if the carriage
path is obstructed during threading, the tool bit
crashes into a workpiece shoulder, the carriage
lock is left applied when the half nut is engaged,
or too deep of a cut is taken, causing a sudden
binding of the tool and workpiece.
it is imperative to recognize, however, that the
shear pin is not a foolproof way of protecting your
lathe from damage if an operational mistake is
made, a chuck-carriage crash occurs, or general
machine overloading occurs on a regular basis.
Always have a few extra pins on hand in case of
an emergency. if a replacement is not on hand,
do not improvise by inserting a roll pin, cotter pin,
steel dowel, or nail. doing so will void the warran-
ty, and can lead to a non-shearing pin, resulting in
catastrophic gearbox damage.
drive hub
leadscrew
optional
Alignment
Marks
Brass shear pin