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When a slipping or mismatched pulley causes positioning errors in your CNC router, 3D printer, or laser engraver, every axis move compounds the problem. Engineers and makers who demand repeatable, backlash-free motion need a pulley machined to tight tolerances — not a generic casting that wobbles under load. These 3M timing belt drive pulleys are designed for exactly that application, serving hobbyist builders, automation integrators, and small-batch manufacturers who cannot afford motion inaccuracy.
Each pulley is machined from aluminum alloy with an anodized or natural finish and is available in two flange configurations: BF-Type (flanged on both sides for positive belt retention) and K-Type (single or no flange for space-constrained assemblies). The 3 mm pitch tooth profile mates with standard 3M open-end or closed-loop timing belts. Belt slot width is 16 mm across all variants. Bore diameters range from 4 mm (≈ 0.157 in) to 25 mm (≈ 0.984 in), with plain-bore and keyway-bore options (keyway dimensions 3×1.4 mm, 4×1.8 mm, 5×2.3 mm, or 6×2.8 mm depending on bore size). Tooth counts span 12 T through 48 T to cover a wide range of drive ratios.
Typical use cases include CNC router X/Y axis drives requiring a 3M timing belt pulley for stepper motor shafts, 3D printer extruder and motion systems using a 3M 20T or 3M 30T drive pulley, and light-duty conveyor or pick-and-place automation where a flanged BF-type pulley prevents belt walk on long unsupported spans.
BF-Type (double-flanged) keeps the belt centered on long or high-speed runs; K-Type (single/no flange) saves axial space in compact assemblies.
12 T to 48 T in a single product family lets you dial in the exact drive ratio without sourcing from multiple suppliers.
Plain bores from 4 mm to 25 mm; keyway bores (3×1.4 mm, 4×1.8 mm, 5×2.3 mm, 6×2.8 mm) for positive torque transmission without set-screw slip.
Matches the 3M belt standard for zero-slip synchronous drive — critical for CNC positioning, 3D printer motion, and stepper motor applications.
Lightweight yet rigid; resists deformation under the radial loads typical of stepper and servo motor drive systems.
Consistent 16 mm slot width across all tooth counts ensures belt alignment and interchangeability within your build.
| Belt Pitch | 3 mm (3M) |
|---|---|
| Tooth Count | 12 T, 14 T, 15 T, 16 T, 18 T, 20 T, 24 T, 25 T, 26 T, 28 T, 30 T, 35 T, 40 T, 48 T |
| Pulley Type | BF-Type (double flange) / K-Type (single or no flange) |
| Belt Slot Width | 16 mm |
| Bore Diameter | 4 mm – 25 mm (see variant options) |
| Keyway Options | 3×1.4 mm / 4×1.8 mm / 5×2.3 mm / 6×2.8 mm (bore-dependent) |
| Material | Aluminum alloy |
| Outer Diameter | See variant options |
| Weight | See variant options |
| Surface Finish | See variant options |
| Compatible Belt | 3M open-end or closed-loop timing belt, 16 mm width |
BF-Type pulleys have flanges on both sides of the belt groove, which physically prevents the belt from walking off the pulley — ideal for horizontal runs, high-speed drives, or any setup where the belt is not guided by a tensioner. K-Type pulleys have a single flange or no flange, saving axial space and weight in compact CNC or 3D printer assemblies where the belt path is already constrained by the frame geometry.
The tooth count determines your drive ratio and linear resolution. For most CoreXY and Cartesian 3D printers, 20 T is the standard choice paired with a 3M belt, giving a well-balanced speed-to-resolution ratio. For CNC routers requiring higher torque at lower speed, a smaller tooth count (12 T–16 T) on the motor pulley increases mechanical advantage. For higher traverse speeds with less torque demand, use 24 T–30 T. Always calculate steps-per-mm after changing tooth count.
A plain bore with a set screw works for light-duty or low-torque applications where the shaft is smooth and the load is modest. A keyway bore is recommended when torque is high, the shaft reverses direction frequently, or you need guaranteed angular registration between the pulley and shaft. Keyway bores eliminate the risk of the pulley rotating on the shaft under shock loads — common in CNC cutting and pick-and-place systems.
NEMA 17 stepper motors typically have a 5 mm output shaft, so select the 5 mm bore variant. NEMA 23 motors commonly use an 8 mm shaft (select 8 mm plain bore or 8 mm keyway bore depending on your torque requirements). Always verify your specific motor's shaft diameter in its datasheet before ordering, as some NEMA 23 motors ship with 6.35 mm (1/4 in) shafts.
No. These pulleys are machined for the 3M trapezoidal tooth profile with a 3 mm pitch. GT2 belts use a 2 mm pitch with a curvilinear tooth profile, and HTD 3M belts use a rounded tooth profile — neither is interchangeable with the trapezoidal 3M profile used here. Using a mismatched belt will cause tooth skipping and accelerated wear. Confirm your belt's pitch and tooth profile before ordering.
The pitch diameter of a 3M pulley is calculated as: PD = (Teeth × Pitch) ÷ π. For example, a 20 T pulley has a pitch diameter of (20 × 3) ÷ 3.1416 ≈ 19.1 mm. The outer diameter is slightly smaller than the pitch diameter for trapezoidal profiles. If your design has a tight clearance envelope, contact us to confirm the exact outer diameter for your selected tooth count before ordering.
These dimensions refer to the keyway width × depth cut into the bore. Larger keyways are paired with larger bore diameters to maintain adequate wall thickness: 3×1.4 mm is used on 8–10 mm bores, 4×1.8 mm on 10–12 mm bores, 5×2.3 mm on 12–17 mm bores, and 6×2.8 mm on 19 mm bores. Match the keyway size to the key already cut on your shaft, or have a machinist cut a matching key slot if your shaft is plain.
