SETUP FOR BEVEL GRINDING:
The point at which the grinding head
tilts is determined by the timing between the amplitude cam and the bevel cam. It is
simply a matter of replacing the idler gear (B36) into the gear train at the correct point
in the grinding cycle. The bevel is designed to occur alternatively for 2 out of every 3
teeth to accommodate a “raker” style setting pattern.
The sequence which the head bevels
{right-left-straight (standard) or left-right-straight (occasional)} is determined by the
orientation of the bevel cam (B23). Noting the positioning of the cam lobes with regard to the
anti clockwise cam rotation checks this. Right-left-straight occurs when high lobe is
followed by the depressed lobe in the anti clockwise rotation. The bevel cam is fixed to
it’s drive gear (B24) by 2xM3 cap screws and removing these allows the bevel cam to
be taken off and turned around so that it’s opposing side is out allowing it to
perform the other bevel sequence.
This requires the motor arm assembly to be first
removed. Loosening the M8x20mm cone point socket set screw (72) in the front plate will
free the entire motor arm assembly allowing access to the cam. Remove the two retaining
M3x10 socket set screws and fit them into the counter bored slots in the other side.
Replace the cam and motor arm assembly. The bevel cam has provision for minor timing
changes to be made by loosening the M3x10mm socket set screws and rotating the cam around
the slots. This allows the timing increments to be finer than the pitch of the gears would
normally achieved.
Set the timing in the following manner:
* With the idler gear removed, press
the Inch Fwd button until the grinding wheel is positioned at the point where the bevel is
required.
* Turn the gear/cam assembly anti clockwise by hand
until the follower bearing moves
into depressed lobe of the cam. This tilts the head
away from the operator. Note there is a 15° dwell on the cam so take this into account
during timing. Teeth bevelled on the back require the cam timing set so that the head has
just tilted as it reaches the top of the tooth (retarded) while teeth bevelled on the
front face require the tilt to be completed as the grinding wheel finishes the face and
enters the gullet (advanced).
* Ensure the grinding wheel is still at the point where
the bevel is required and the bevel cam is correctly positioned with the cam follower in
the depression, then move the idler gear (B36) and tighten with the M6 pan head screw
through the slot in the rear plate so that the gear completes the gear train.
Note: The bevel cam/gear rotates anti clockwise
and there is a 15° dwell. Failure to take account of this dwell with regard to where the
bevel is to be applied will result in the head being tilted in the gullet.
Further minor adjustment is the made by
loosening the 2 screws retaining the cam to its driven gear and rotating cam until the exact timing is obtained. Retighten
the cam retaining screws.
The grinding head alternatively bevels twice every
three teeth and it is important to ensure that the tilt sequence and direction corresponds
to the setting sequence of the blade. Blades are normally left - right - straight but
sometimes right - left - straight teeth are encountered. This requires the Bevel Cam to be
removed from the driven gear and inverted as described previously.
Before beginning to sharpen blades, it is important
that the grinding wheel is centred (as previously described) and the head is free to
rotate.
With a blade fitted to the machine and
the head suitably timed for the blade (either the front or back of the tooth to be
bevelled), inch the machine until the grinding wheel has reached it’s full tilt
(either side) at the appropriate point along the tooth profile and lower the grinding head
until the wheel just touches the tooth. Index the machine until the head bevels at the
same point on the alternate tooth. Check the gap distance between the wheel and the tooth
to ensure the wheel is centred.
The head tilt is controlled via a push rod in the
middle of the motor arm. This axial motion is transferred to tilt the head through a
reciprocating worm rack engaging a segmented gear attached to the head pivot.
To ensure smooth operation, it is important that the
backlash between the rack and the gear is eliminated without any preloading, which may
cause the movement to stick. Adjusting this backlash is achieved by rotating the eccentric
bush (B6) around the motor arm (B17). Loosen the M3x6 retaining screw (B4) and using it as
a lever, move it within the arc allowed by the slot. Moving the screw in the slot towards
the operator removes the backlash. Tighten only enough to remove excess movement and then
retighten the screw.
