What should I check on the food-contact surfaces of a meat grinder?

On a grinder's food-contact surfaces, brightness of the housing tells you little. Run a hand over the auger, worm and both faces of the plate for tool marks or burrs, and inspect welds for porosity or unfinished seams. The real trouble spots are internal corners, the clearance between auger and barrel, and the back of the plate, where meat paste lodges. Ask for the contact-material certificate and a layout drawing, and ideally handle a spare plate to judge machining quality. After a trial run, rinse with warm water, strip the head and check for residue; tool-free, quick-breakdown design matters if you change recipes often. Accept the unit only when it wipes clean with no film after washing.