Toro GR 105 Fundamentals page 22

20 Fundamentals of Reel Mowers
It is important to understand that Toro reel
mowers are designed and manufactured to
optimize available power from the engine and
hydraulic systems. To help do this, we put a
"relief" on every reel blade to reduce the width
of reel blade that contacts the bedknife. This
has been proven to reduce power
requirements, as well as allow the machine to
operate more efficiently. This can be very
important, depending on the terrain, type of
grass and amount of grass being cut.
Toro has two different methods of
manufacturing reel blades with a "relief". The
reel blades are made from straight stock steel
and then are either relief ground or the relief is
milled in. Either way, there is a relief on the
blade when it is manufactured. A small ground
relief is also put on milled relief blades during
manufacture.
There are two methods of grinding reels. This
slide illustrates Spin Grinding (which is also
know as "Flat Grinding").
With this method, both the reel and the
grinding stone are turning as the reel is being
sharpened. It is sometimes stated that
backlapping is not required after spin grinding,
because the reel is a perfect cylinder when
grinding is completed. This depends on proper
alignment of the reel in the grinder before
sharpening. Also, the bedknife and bedbar
must be straight and perfectly parallel to the
reel when it is mounted. Backlapping will
remove burrs and rough edges, producing a
honed edge that will cut grass evenly.
If using a spin grinder to sharpen straight stock
reel blades (such as on fairway mowers) some
or all of the relief will be ground off. If you are
going to restore the relief that was on the
blade when was manufactured, you will need
to also use the other method of grinding
(single blade "relief" grinding). It is
recommended to do the relief grinding first,
then spin grind to restore the reel to a cylinder
shape.
TORO® Service Training