Textron Jacobsen Super LF 1880 Fairway Mower with ROPS, Service & Repair Instructions

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ATTACHMENTS
12E-12
BEDKNIFE FRONT FACE ANGLE
If grass is to be cut at the desired height, it must con-
tact the front edge (front face) of the bedknife at the
proper angle. This front face angle is called the “front
face relief” angle.
Without a relief angle to the bedknife front face, the
grass blades would contact the lower edge of the bed-
knife and simply fold over and not be lifted to an angle
where they could be cut by the reel blades.
The proper bedknife front face relief angle for all
Jacobsen reel mowers is 0° to 5° (Figure 12E-2). The
height thickness of the front face must be taken into
consideration when grinding the relief angle. Regard-
less of the height of the front face, the relief angle is
measured from top of the bottom of the front face, not
from the top to bottom of the front of the bedknife.
Figure 12E-2. Front Face Grinding Angle
BACKLAPPING
General
Lapping is to be considered a honing process and
should not be used to sharpen an extremely dull or
damaged reel or bedknife.
Lapping is not a substitute for grinding. Lapping can
maintain a sharp edge — it does not create a sharp
edge.
Lapping (backlapping) is the method of removing nicks,
burrs, and other minor obstructions to clean cutting.
During the lapping process (Figure 12E-3), the reel-to-
bedknife clearance is adjusted until the reel and bed-
knife are in contact. There is no clearance in lapping.
Lapping compound is applied to the relief area of the
reel blades.
When the reel is turned on the backward direction
shown, lapping compound is forced between the top of
the bedknife and the “land” (or cutting edge) of the reel
blade.
The grit in the lapping compound acts like sandpaper
to hone the cutting edges of both the bedknife and the
reel blades. Only a small amount of metal, 0.005 in
(0.127 mm), or less should be removed by lapping.
Beyond that point, the lapping process actually
destroys the cutting surface.
Figure 12E-3. Lapping Process