Maintenance Instructions REPLACING/REPAIRING
61
Blade Overload Shear Bolts
The cutting blade is keyed to the blade hub by two
(2) shear bolts (10-24 x 5/8 in. stainless steel ma-
chine screws). These bolts are designed to shear
and protect the blade drive gearbox from damage if
the blade encounters a shock load.
Cutting Blade Shear Bolts
NOTE: Tightening the 5/8-18 blade mounting nut
to 60 ft-lb (81.3 N
·m) is also important for proper
shock load protection. It is important to not over-
tighten the mounting nut since this defeats (over-
rides) the function of the shear bolts.
If these bolts shear, remove the blade and install
new bolts. Refer to CHECKING/SERVICING in this
section for Sharpen Mower Blades which describes
the blade removal and installation procedure.
After reinstalling the blade, check blade timing by
moving blades through one (1) complete revolu-
tion. Make sure blade tips pass clear of each other.
If timing is incorrect, refer to Mower Deck Gearbox
Replacement in this section.
PTO Shear Pin
The PTO drive shaft connection to the deck gearbox
has a shear pin to provide shock load protection to the
mower deck drive. This system provides primary
shock protection in case of blade impact and will
normally shear before the individual shear bolts on
the blade hub.
When the PTO pin has sheared, use the following
procedure to replace it:
1. Loosen the two bolts securing the PTO shaft
guard on the deck; lift the guard off. (Holes in
guard are slotted for easy removal.)
2. Rotate U-joint on shaft to align the shear pin hole
with the hole (and shear pin fragment) in the
shaft. Use a punch to drive the remaining portion
of the old shear pin out.
3. Install new shear pin and secure with cotter pin.
PTO Shear Pin
IMPORTANT: Use only Walker P/N 8067-13
shear pins for replacement to provide proper
shock protection -- these pins are hardened to
shear under a specific amount of load.
4. Reinstall the PTO shaft guard.
Before operating the deck, inspect the blade over-
load shear bolts and also check blade timing (on gear
driven decks) by moving blades through one (1)
complete revolution. Make sure blade tips pass
clear of each other. If timing is incorrect, refer to
Mower Deck Gearbox Replacement in this section.
Mower Blades
Mower blades are removed and remounted as de-
scribed in the Sharpen Mower Blades instructions.
During the course of sharpening and inspecting
mower blades, if there are any of the following con-
ditions of wear or damage, blades should be re-
placed for reasons of safety and performance of the
machine:
• An excessive amount of the flat section of the
blade has been ground away (removed) when the
blade is sharpened. Replace the blade when less
than a 3/4 in. (19 mm) flat section remains at the
blade tip.
Cutting Blade
Shear Bolts
Cotter Pin
U-Joint
Tube Assembly
Shear Pin
Split Spring Pin
U-Joint
Shaft Assembly
Set Screw
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