Metal-to-Metal Program

A metal-to-metal program is a routine of inspections and repairs that finds places where metal parts rub, scrape or strike each other, so shavings and fragments are stopped before they reach food.

  • Food safety
  • Physical hazards & pests

A metal-to-metal program targets one specific source of metal contamination: moving metal parts in contact with other metal. FDA guidance names metal-to-metal contact, as in mechanical cutting and blending, as a way fragments get into food. It also lists parts that can break loose, such as wire-mesh belts, screens and metal ties, and worn parts such as mixer blades and saw blades. A program maps these contact and wear points, schedules visual checks for damaged or missing parts, and sends findings to maintenance so worn parts are fixed before a fragment breaks free.

Metal fragments are a physical hazard. FDA has supported regulatory action for pieces about 7 to 25 mm long, and smaller pieces can harm vulnerable people. End-of-line detection has limits: FDA notes stainless steel is difficult for metal detectors to find, and calibration, product acidity, humidity and fragment orientation all affect results. Stopping metal from shedding in the first place reduces reliance on detectors. Federal CGMP rules also require adequate measures against metal in food and equipment that is properly maintained.

Key facts

Fragment size FDA acts on
About 7 to 25 mm (0.3 to 1 inch)
FDA example equipment checks
Before start-up, every 4 hours, end of day, after malfunctions
USDA AMS detector test (poultry, before packaging)
1.5 mm stainless steel strip, at least hourly
Hardest common metal to detect
Stainless steel

In a bakery or commercial kitchen

  • List every point where metal can touch metal, such as mixer blades and bowls, cutting blades, wire-mesh belts and screens
  • Check those parts before start-up and at set intervals; FDA's example uses start-up, every 4 hours and end of day
  • Hold product made since the last good check if a part is broken or missing, then find and fix the cause
  • Back up prevention with magnets, screens or metal detectors, and verify detectors with known-size test pieces on a schedule
  • Keep equipment adequately maintained, as CGMP rules require, and record each repair and part replacement

For home and cottage bakers

  • Check stand-mixer beaters, dough hooks and whisks for chips or damage, since worn mixer blades are a known source of metal fragments

Related entries

Sources

Written by VanillaGoods in our own words from these sources. Last reviewed October 17, 2026.

  1. Fish and Fishery Products Hazards and Controls Guidance, Chapter 20: Metal Inclusion, U.S. Food and Drug Administration
  2. Hazard Analysis and Risk-Based Preventive Controls for Human Food: Draft Guidance for Industry, Chapter 4 (Preventive Controls), U.S. Food and Drug Administration
  3. 21 CFR 117.80 Processes and controls, Legal Information Institute, Cornell Law School (Code of Federal Regulations)
  4. 21 CFR 117.40 Equipment and utensils, Legal Information Institute, Cornell Law School (Code of Federal Regulations)
  5. QAD 609 Procedure: Metal Detection, USDA Agricultural Marketing Service