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Engineers and makers building CNC routers, 3D printers, or robotic actuators know the frustration of belt slip and misalignment caused by poorly toleranced pulleys. These 3M K/BF-type timing belt pulleys are designed for builders who need repeatable, slip-free power transmission in compact drive systems where every millimeter of accuracy counts.
Each pulley is machined from aluminum alloy with a natural or anodized finish and features a 3M tooth profile (3 mm pitch). Available in two flange styles — BF-type (double-flange) and K-type (single-flange) — with tooth counts from 20T to 30T and bore diameters ranging from 4 mm (0.16 in) to 17 mm (0.67 in). All variants are matched to a 10 mm (0.39 in) belt width.
Typical applications include DIY CNC gantry drives requiring 3M synchronous belt pulleys, desktop 3D printer X/Y axis timing pulley replacements, and lightweight robotic arm joint drives where a low-profile aluminum timing pulley with set-screw bore is needed for precise indexing.
Choose BF-type (double-flange) for guided belt tracking or K-type (single-flange) for open-track and tandem drive setups — both share the same 3M tooth geometry.
Available in 20T, 22T, 24T, 25T, 28T, and 30T to let you dial in the exact gear ratio your drive system requires without custom machining.
Bore diameters from 4 mm to 17 mm (including 6.35 mm / 1/4 in and 12.7 mm / 1/2 in imperial sizes) cover most stepper motor and servo shaft standards out of the box.
Lightweight yet rigid aluminum body keeps rotational inertia low — critical for high-acceleration CNC and robotics applications where motor response time matters.
Each pulley includes a set-screw bore for secure shaft fixation without adhesives, allowing quick swaps during prototyping or maintenance cycles.
Each unit is a single pulley — order the exact quantity you need for your drive system without paying for surplus stock.
| Belt Pitch | 3M (3 mm) |
|---|---|
| Applicable Belt Width | 10 mm (0.39 in) |
| Tooth Count Options | 20T / 22T / 24T / 25T / 28T / 30T |
| Bore Diameter Range | 4 mm – 17 mm (0.16 in – 0.67 in) |
| Available Bore Sizes | 4, 5, 6, 6.35, 7, 8, 10, 12, 12.7, 14, 15, 16, 17 mm |
| Flange Style | BF-type (double-flange) / K-type (single-flange) |
| Material | Aluminum alloy |
| Bore Retention | Set-screw |
| Outer Diameter | See variant options |
| Hub Length | See variant options |
| Weight (per unit) | See variant options |
| Quantity per Order | 1 piece |
BF-type pulleys have flanges on both sides of the tooth face, which keeps the belt centered and prevents lateral drift — ideal for single-pulley drive stages. K-type pulleys have a flange on one side only, making them better suited for tandem or multi-pulley arrangements where the opposing pulley provides the second guide surface.
Standard NEMA 17 stepper motors have a 5 mm output shaft. Select the 5 mm bore variant. If your motor has a D-cut shaft, ensure the set-screw is tightened against the flat for a secure fit.
The speed ratio between two pulleys equals the ratio of their tooth counts. For example, pairing a 20T drive pulley with a 30T driven pulley gives a 1.5:1 reduction. Choose your tooth counts based on the desired linear speed or torque multiplication for your specific axis.
No. These pulleys use a 3M tooth profile (3 mm pitch, trapezoidal). They are not interchangeable with GT2 (2 mm pitch) or HTD 3M (curvilinear profile) belts. Always match the pulley tooth profile to your belt profile for correct meshing and load transfer.
Aluminum alloy pulleys are well-suited for light-to-medium duty CNC, 3D printing, and robotics applications. For continuous high-torque industrial drives or environments with heavy side loads, verify that the pulley's rated torque capacity meets your application requirements before ordering.
Aluminum alloy naturally forms a thin oxide layer that provides moderate corrosion resistance. For consistently humid or mildly corrosive environments, an anodized finish variant (where available) offers additional protection. For harsh outdoor or chemical exposure, consider stainless steel alternatives.
Yes. 6.35 mm is the metric equivalent of 1/4 inch (0.25 in), so the 6.35 mm bore variant is the correct choice for standard 1/4-inch motor or drive shafts. Tighten the set-screw firmly to prevent rotational slip under load.
