Why does a meat grinder knife become unusually hot?

Overheating at the grinder knife usually points to mechanical fit, not just fast feeding. Check first for a dull or chipped edge: a blunt blade pushes meat instead of shearing it, so friction climbs sharply. Then inspect the knife-to-plate contact face for trapped sinew, bone chips or misalignment; either too much or too little clearance creates local rubbing. Warm or unevenly frozen raw material and rising feed resistance add heat as well. Stop the machine, measure in-feed and out-feed temperatures, look for rub marks and metal swarf around the plate, confirm motor current stays within rating, and reset clearance to the maker's spec. Never mask a fit fault by slowing feed. On the first unit, judge acceptance by cross-checking edge condition, contact clearance and current trace together.