Timing pulley flanges are used to maintain belt contact with a timing pulley in power transmission applications. Typically, stock pulleys include options for flanges. Separate flanges are available for custom pulleys made from pulley stock. Timing pulley flanges are manufactured to fit timing pulleys of the same pitch and size. The dimensions of a pitch, including the mating flange, are specified by the number of grooves. Pulley pitch is the distance from the midpoint of one tooth to the midpoint of an adjacent tooth. Timing pulley flanges are available in both English and metric units. English pitch is specified in inches (in.) or fractions of an inch. Lettered designations include L, H, and XL. Metric pitch is specified in millimeters (mm). Letter designations include GT and HTD.
Metal Timing Pulley Flanges
Timing pulley flanges are made from metals such as aluminum, steel, carbon steel, alloy steel, hardened steel, and stainless steel. Aluminum is bluish, silver-white, malleable, ductile, light, metallic element with good electrical and thermal conductivity, high reflectivity, and resistance to oxidation. Aluminum is lighter and less strong than steel, a form of iron that contains carbon in any amount up to about 1.7 percent as an essential alloying constituent. Many grades of carbon and alloy steels are used in timing pulley flanges. Hardened steel is another common material choice. Stainless steel is chemical and corrosion resistant and can have relatively high stress ratings. It does not require anti-corrosion coatings, but cannot be hardened to same degree as carbon steels
Plastic Timing Pulley Flanges
Timing pulley flanges are made from plastics such acetal, nylon, and polycarbonate. Acetal, polyacetal or polyoxymethylene (POM) provides a higher strength material than polyethylene-type polymers; however, polyacetal materials are susceptible to oxidation at elevated temperatures. Nylon, comprising several grades of polyamides, is a widely used, general-purpose material. It is tough and resistant and has good pressure ratings. Nylon 6/6 is a grade commonly used for timing pulley flanges. Polycarbonate is an amorphous material with excellent impact strength, clarity, and optical properties. Polycarbonate has excellent mechanical properties, and can be molded to tight tolerances for timing pulley flanges. Brand names include: Caliber® (Dow), Lexan® (GE), Makrofol® and Makrolon® (Bayer).