MIL-C-52128C
less than 3/4 inch deep measured from crest to valley. The jaw plates shall be removable for
replacement without removal of other accessories or components except cheek plates and
wedges. The jaw plates shall have inserts for attaching lifting eyes or similar means for
removing or inserting new jaw plates. Cheek plates shall be mounted on the frame between both
sides of the jaw plates to protect the frame during the crushing operation. The cheek plates shall
be constructed of two or more replaceable pieces and shall not loosen and shift during the
crushing operation.
3.12.3 Pitman. The pitman shall be made of cast or fabricated steel reinforced with ribs and
shall be machined to receive the movable jaw plate. Cast steel when used shall be in accordance
with ASTM A148 with analysis and heat treatment as recommended by the manufacturer of the
crushing component. Fabricated steel, when used, shall be stress relieved in accordance with
American Welding Society codes for weldments of this size. At the lower, or toggle end of the
pitman, provision shall be made to receive a renewable toggle seat.
3.12.4 Pitman shaft bearings. The pitman and pitman shaft shall be mounted on antifriction
bearings. The bearings shall be protected by labyrinth-type grease and dust seals which shall
prevent dust and other foreign matter from entering the bearings. The bearings shall conform to
FF-B-185 or FF-B-187, except that taper bore bearings and taper sleeve adaptors will be
permitted.
3.12.5 Pitman shaft. The pitman shaft shall be an eccentric shaft machined from steel
conforming to SAE 4140, 4340, or 6150, heat-treated, and shall withstand the maximum
crushing load. The main shaft bearings shall be mounted in bearing housings on the crusher
frame.
3.12.6 Flywheels. Two flywheels of gray iron conforming to ASTM A48, Class 35, 40, 45,
50, 55, or 60 shall be mounted on the pitmin shaft, shall be counterbalanced to offset the mass of
the eccentric revolving parts, and shall be of sufficient size to provide inertia to transmit and
equalize the energy necessary for crushing the rock specified in 3.1 at maximum crusher
capacity, without reducing the flywheel speed by more than 10 percent from the flywheel speed
when the crusher is operating empty. One flywheel shall be machine-grooved for V-belts, and
used as a driving pulley.
3.12.7 Toggle plate. A cast iron or steel toggle plate shall be provided to rest between the
toggle seat on the pitman and the seat in the toggle wedge of the adjusting mechanism. The
toggle plate shall be held in place by means of a tension bolt and shall be spring arranged so that
the bolt will not bind or bend during operation and adjustment. The toggle plate shall be
constucted so that it will break or deform when uncrushable material such as tramp iron enters
the crushing component, and shall fail before any other part of the crusher is stressed so as to
cause breakage or permanent deformation. The toggle plate shall not break when crushing rock
as specified herein.
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