MTD 550 Series Operator's Manual page 11

Trenching (Ifequipped)
You can utilize the edger's optional trenching feature in order
to create a wider cutting path for such things as laying wire for
landscape lighting.
1.
WARNING! Disconnect the spark plug wire and
ground against the engine before performing the
following steps.
WARNING! The edger blade is sharp. Wear leather
work gloves to protect your hands when working
around the edger blade.
Use two wrenches (one wrench to prevent the hex bolt
head from spinning and the other to unthread the flange
nut) to remove the flange nut that secures the edger blade,
leaving the edger blade in place. See Fig. 5-4.
\
Figure 5-4
2. Install the additional edger blade supplied with your
machine and the flat washer. See Fig. 5-4.
3. Secure with the flange nut removed earlier. Use a torque
wrench to tighten the flange nut to between 37 foot-lbs.
and 50 foot-lbs.
NOTE: Make certain that the drive belt is seated correctly
on the blade spindle and that it is riding smoothly on the
spindle sheaves and is not pinched between them. Repeat
the first three steps if belt is pinched.
SECTION S -- OPERATION
11