Spearhead TWIGA
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Sharpening the knife
After five to twenty operating hours, depending on the work involved, the knives require
resharpening. It is recommended that the knives be removed from the cutterbar for
resharpening. The procedure is as follows:
Switch off tractor and remove the starting key. Disconnect the con rod, remove the
three setscrews securing the knife heel to the knife and withdraw the knife from the
cutterbar.
Clean the knife and ensure that neither the back nor the knife sections are bent if
required, straighten as necessary. A cutting angle of 35°- 40° is required. A high
speed hand grinder should be used, with ideally, a pot shaped pencil grinder of
approximately 1” (25mm) diameter by 1 3/8” (35mm) long. Grinding is carried out
with the end face of the grinder moving from the base of the knife section up to the
points.
It is possible to re-sharpen the knives in situ, the procedure is as follows:
Position the cutterbar on or parallel to the ground. Switch off the tractor engine and
disconnect the con-rod. Manually position the knives so that they cover the fingers and
clamp together in this position. Sharpening with files is not recommended as the process
tends to leave small burrs on the edge which curl under when the knife is replaced thus
impeding the free movement of the knife and leaving a blunt cutting edge.
DANGER: It is imperative that great care is adopted at all times when working with
the cutterbar to avoid injury – the use of safety gloves and safety glasses is
recommended at all times when working with this and all associated components.
