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When your CNC router, 3D printer, or automation rig demands slip-free, repeatable motion, the wrong pulley becomes the weakest link in the entire drive train. Engineers and makers who need a reliable XL timing belt pulley with a secure bore fit — without the hassle of set-screw slippage — will find the clamping-style BF and K designs in this listing purpose-built for that job.
Each pulley is machined from aluminum alloy with an anodized finish, featuring an XL-pitch tooth profile (5.080 mm / 0.200 in pitch). Bore diameters range from 5 mm to 20 mm (approx. 0.197 in – 0.787 in), and tooth counts span 15, 18, 20, 24, and 25 teeth. The BF-type uses a through-bore with flanges on both sides; the K-type adds a clamping collar for tool-free shaft retention.
Typical use cases include desktop CNC gantry drives requiring backlash-free XL belt pulleys, stepper-motor output shafts on laser engravers needing a 5 mm bore XL pulley, and servo-driven conveyor systems where a 20-tooth or 24-tooth XL timing pulley keeps indexing accurate across thousands of cycles.
Choose BF-type (flanged through-bore) for standard belt tracking, or K-type (clamping collar) for tool-free shaft locking — both eliminate set-screw marks on precision shafts.
Available in 5, 6, 6.35, 7, 8, 10, 12, 12.7, 14, 15, 16, 17, 18, 19, and 20 mm bores to fit stepper, servo, and NEMA motor shafts without adapters.
Standard 5.080 mm (0.200 in) XL pitch ensures direct interchangeability with off-the-shelf XL timing belts used in CNC, robotics, and lab automation.
Lightweight aluminum body with anodized surface treatment resists corrosion and wear, keeping tooth geometry accurate over extended duty cycles.
15, 18, 20, 24, and 25-tooth options let you dial in exact speed ratios and torque multiplication for your specific drive design.
Integrated flanges on BF-type pulleys keep the XL belt centered on the pulley face, reducing edge wear and preventing belt walk in high-cycle applications.
| Belt Type | XL (Extra Light) |
|---|---|
| Belt Pitch | 5.080 mm (0.200 in) |
| Pulley Type | BF-type (flanged) / K-type (clamping collar) |
| Number of Teeth | 15 / 18 / 20 / 24 / 25 (see variant options) |
| Bore Diameter | 5 – 20 mm (see variant options) |
| Material | Aluminum alloy |
| Surface Finish | Anodized |
| Flange | Both sides (BF-type); See variant options (K-type) |
| Outer Diameter | See variant options |
| Hub Width | See variant options |
| Quantity per Order | 1 PCS |
The BF-type has flanges on both sides of the tooth face and uses a standard through-bore — ideal when you want belt tracking and plan to secure the pulley with a key or set screw on your own. The K-type adds a clamping collar that tightens around the shaft without a set screw, making it easier to reposition and less likely to damage polished motor shafts. Choose K-type when you need tool-free adjustment or frequently swap pulleys during prototyping.
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, the clamping K-type is recommended for a more secure grip. For NEMA 23 motors with an 8 mm shaft, choose the 8 mm bore option.
Use the same tooth count on both the drive and driven pulleys for a 1:1 ratio. For example, pair a 20-tooth pulley on the motor with a 20-tooth pulley on the driven shaft. To reduce speed and increase torque, use a smaller tooth count on the motor side and a larger count on the driven side (e.g., 15T drive → 25T driven = 1:1.67 reduction).
Yes. These pulleys follow the standard XL pitch of 5.080 mm (0.200 in), which is an industry-wide specification. They are compatible with any XL-pitch timing belt of the appropriate width. Confirm the belt width matches the pulley's tooth face width before ordering.
The anodized aluminum surface provides moderate corrosion resistance suitable for indoor automation, light industrial, and workshop environments. For prolonged outdoor exposure or high-humidity conditions, consider applying a light machine oil to the bore and tooth surfaces periodically. These pulleys are not rated for submersion or marine environments.
Yes. The 6.35 mm bore variant is specifically included to accommodate 1/4-inch imperial shafts common in North American servo motors and hobby CNC spindles. Select "6.35mm & 1PCS" from the Bore Diameter option when ordering.
Specific RPM and torque ratings depend on the belt width, tension, and application load — values that vary by installation. As a general guideline, aluminum XL pulleys in this size range are commonly used in applications up to 3,000 RPM with light-to-medium loads typical of desktop CNC and 3D printing. For high-torque or high-speed industrial applications, contact us to confirm suitability.
