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When your CNC router, 3D printer, or robotic actuator demands consistent torque transfer without slippage or premature wear, the gear material and geometry matter enormously. Hobbyists and engineers alike struggle to find spur gears that balance dimensional accuracy with genuine mechanical strength — this 2 Module 45# carbon steel series is engineered to meet that need across a wide tooth-count range.
Each gear is machined from 45# medium-carbon steel, a grade known for its balanced hardness and machinability. The module is 2 (metric), with a face width (thickness) of 20 mm (approximately 0.79 in). Tooth counts span from 12T to 95T, giving you pitch diameters ranging from approximately 24 mm (0.94 in) for the 12T up to 190 mm (7.48 in) for the 95T. Bore diameter varies by tooth count — see variant options for exact bore dimensions.
Typical use cases include: drive-train assemblies in desktop CNC milling machines requiring precise feed-rate control; extruder and Z-axis drive systems in FDM 3D printers where backlash must be minimised; and custom robotic joint mechanisms where a compact, high-strength gear pair is needed for repeatable positioning.
| Module | 2 (Metric) |
|---|---|
| Material | 45# Carbon Steel |
| Face Width (Thickness) | 20 mm (0.79 in) |
| Tooth Count Range | 12T – 95T (see variant options) |
| Pitch Diameter | Module × Teeth (e.g. 2 × 20T = 40 mm) |
| Pressure Angle | 20° |
| Bore Diameter | See variant options |
| Tooth Profile | Involute |
| Surface Finish | Machined, lightly deburred |
| Quantity per Order | 1 piece |
Determine your required gear ratio first: divide the driven shaft speed by the driving shaft speed. For example, a 3:1 reduction with a 20T pinion requires a 60T gear. Then confirm the resulting pitch diameter (Module × Teeth) fits within your housing clearance. Use the formula: Pitch Diameter (mm) = Module × Number of Teeth.
Bore diameter varies by tooth count and is listed in the variant options on this page. Smaller tooth counts (12T–20T) typically have smaller bores, while larger gears accommodate larger shaft diameters. If you need a custom bore size, the steel is machinable and can be bored out by a local machine shop.
Yes. 45# carbon steel has a typical tensile strength of 600–800 MPa and yield strength around 355 MPa, which is well-suited for the intermittent, moderate-torque loads found in desktop and mid-size CNC router feed systems. For heavy industrial cutting with continuous high-torque demand, consider a hardened or alloy steel gear.
45# carbon steel will oxidise if left unprotected in humid or wet environments. For typical indoor workshop use, the machined surface provides adequate short-term protection. Apply a thin coat of machine oil or anti-rust spray if the gear will be stored or used in a high-humidity environment. For outdoor or washdown applications, consider stainless steel gears instead.
Yes. Any Module 2 spur gear in this range will mesh correctly with a Module 2 rack (straight or helical rack with the same normal module). Ensure the rack's pressure angle also matches 20° for proper tooth engagement and minimal backlash.
Centre distance = (Pitch Diameter of Gear 1 + Pitch Diameter of Gear 2) ÷ 2. For example, a 20T and a 40T Module 2 gear pair: (40 mm + 80 mm) ÷ 2 = 60 mm centre distance. Always add a small clearance (typically 0.1–0.2 mm) to account for manufacturing tolerances and thermal expansion.
Keyway and set-screw configurations vary by tooth count and are noted in the variant details. If the listing does not specify a keyway, the bore is plain (smooth). A set-screw or keyway can be added by a machine shop if required for your shaft retention method.
