Cam actuated power sources for clamp post

   The clamp posts are used mainly for actuating the fixture clamps, like internal collets (stationary), chucks, pusher clamps, internal clamps and secondary for raising and jacking-up the workpiece. The clamp posts could be push-up or pull-down in reference of force direction. Some of them (like the one in the figure below) are made to retract the clamp post for unclamping, whilst the other use aditional power source (like springs) for this operation.  The cam angle should be between 7 to 12 degrees in order to use the produced friction for static seal. Hammer action is required in order to break this seal (see  hammer action article http://www.buyblueprint.com/article/50/).

   Another characteristic that distinguish the cam actuated power sources for clamp post is the position of the sliding axles of the two shafts. The clamp post and the cam pushing-pulling shaft could be on the same plane or with an offset distance between them. Their projected angle is usually 90 degrees. This characteristic could be very useful when there are difficulties have them both at coplanar. When we are using bearings for contacting the cam surface and transferring the forces, we must remember that due to friction reduction (rolling not sliding), the cam must be constantly forced from the actuating force. If not the cam will return and the clamping force will be reduced. The appropriate bearing for clamp posting is the cam follower with hub or the needle roller bearing, due to their form (small outer diameter in reference to the inner one).

   Another detail is the appropriate design of the mating parts. Always assure that burrs will not dragged by the clamp post movement inside the sliding surfaces. In order to keep them out provide your design with dust protectors and special shields (see dust protection article http://www.buyblueprint.com/article/35/) or with simple seals. Provide with adequate spacing, large enough to allow the cam to pass within the clamp post as they are assembled when they are in their sliding bores. Periodical lubrication (not for the cam surfaces) and linear bushings remove friction and make the fixture power source more efficient.