Stripped sprue pivot

Stripped sprue plate screws are usually the result of no lube or lack of lubricant on the sprue pivot. A lack of lube on the sprue pivot causes the sprue bushing to rotate with the sprue plate, rather than remain fixed to the mold block as intended. This in turn causes the sprue plate retaining screw to loosen, so the operator must continually re-tighten it into the hot aluminum mold block, which is softer when heated to around 500 degrees.