The Snap-Trap Self-Closing Guard is located inside the wheel guard and is positioned above the grinding wheel.  The guard is an arc of fabricated steel supported by a series of pins.  In case of a wheel accident, grinding wheel fragments strike the cross webs, welded inside the guard, causing the guard to rotate and create a barrier between the operator and the wheel.  The force of the wheel fragments impacting the Snap Trap shears the shear pin located near the rear of the guard.  The 1/4" brass shear pin holds the guard in position during the normal machine operation.

Since the guard is located above the wheel and sits on pins, grinding grit buildup should be minimal.  However, the Snap Trap guard should be visually inspected for any buildup and any excessive wear.  The Self-Closing Guard should be checked for ease of rotation.  The following explains the procedure for this inspection.

Besides the shear pin, the guard also includes a set screw.  The set screw is used for assembly and alignment purposes and has been properly adjusted at the factory.  If the set screw is readjusted in the field, it is possible, under certain circumstances, for the set screw to interfere with the Snap-Trap guard.  When properly adjusted, the set screw does not lock the Snap-Trap guard against the opposite wall.  The set screw length is such that when the head of the socket head set screw is flush with the side member of the guard, the end of the set screw will be approximately 1/16" away from the Snap-Trap guard.

The drawing R060025 indicates the location of the set screw.  This screw is located on the side of the guard member immediately inside the guard door.  Check the machine to make sure that the set screw is properly adjusted and not binding on the Snap-Trap Self-Closing Guard.

Drawing R060026 shows the approximate location of the shear pin.  The pin should be driven out from the outside of the wheel guard to the inside of the wheel guard.  Check the rotation of the Snap-Trap Self-Closing Guard by slightly lifting the guard and rotating it towards the Tool Rest.  After inspection, return the guard to its open position and replace the shear pin.  The pin should be flush with the outside of the guard and extend beyond the movable part of the guard approximately 1/8".  The shear pin is made of 1/4" diameter soft brass rod, approximately 1-3/8" long.

Inspections should be performed at regular intervals depending upon severity of use of the grinder.  However, the interval should not exceed six months.  If the Self-Closing Guard cannot move properly, operator injury may occur in the event of a major wheel failure.

This machine is designed for wheels 1½" to 3" wide.  Use of a wheel less than 1½" wide or an excessively worn larger wheel may prevent the proper operation of the Snap-Trap.  The smaller wheel may not contain sufficient energy to shear the pin in the event of a wheel breakage.  The factory can supply information relative to possible modifications of the shear pin to allow such operations.