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When your motion system demands repeatable, slip-free power transfer, a mismatched or worn pulley is the first point of failure. Engineers, makers, and machine builders who rely on synchronous belt drives need a pulley that holds tight tolerances across every cycle. These S3M-BF timing pulleys are machined to suit 10 mm wide S3M (3 mm pitch) belts and are available in a wide tooth count range from 30 T to 48 T, making them a versatile fit for both compact and extended drive systems.
Each pulley is machined from aluminum alloy with a natural or anodized finish. The bore diameter ranges from 4 mm to 25 mm (approx. 0.16 in to 0.98 in), and the tooth count spans 30 T to 48 T. The hub width is typically around 11 mm. Variants are available with or without a keyway (keyway widths of 3 mm, 4 mm, 5 mm, 6 mm, or 8 mm depending on bore size), allowing direct shaft mounting or keyed shaft coupling.
Typical use cases include desktop 3D printer X/Y axis drives, CNC router gantry systems, robotic arm joint actuators, conveyor indexing mechanisms, and DIY automation projects requiring precise linear or rotary motion control with S3M synchronous belt drives.
Available from 30 T to 48 T, covering a broad range of gear ratios and drive configurations for both compact and extended belt runs.
Bore diameters from 4 mm to 25 mm (approx. 0.16–0.98 in) accommodate a wide variety of motor and shaft sizes without custom machining.
Select variants include a precision-cut keyway (3 mm, 4 mm, 5 mm, 6 mm, or 8 mm width) for positive torque transmission on keyed shafts, eliminating rotational slip under load.
The 3 mm pitch S3M tooth profile ensures accurate meshing with S3M belts, delivering consistent indexing and low backlash in positioning applications.
Lightweight yet rigid aluminum alloy body keeps rotational inertia low while providing sufficient strength for typical servo and stepper motor drive loads.
The BF (both-side flange) configuration keeps the belt centered on the pulley during operation, reducing lateral belt wander and extending belt service life.
| Belt Type | S3M (3 mm pitch, 10 mm wide) |
|---|---|
| Number of Teeth | 30 T / 32 T / 34 T / 35 T / 36 T / 38 T / 40 T / 42 T / 44 T / 45 T / 46 T / 48 T |
| Bore Diameter | 4 mm – 25 mm (see variant options) |
| Keyway Width | Without keyway / 3 mm / 4 mm / 5 mm / 6 mm / 8 mm (see variant options) |
| Hub Width | Typically 11 mm |
| Flange Type | BF (Both-side Flange) |
| Material | Aluminum alloy |
| Finish | See variant options |
| Outer Diameter | See variant options |
| Quantity per Order | 1 piece |
The tooth count determines the pulley's pitch diameter and affects your drive ratio. For a 1:1 ratio, use matching tooth counts on both pulleys. To increase speed at the output, use a smaller driven pulley; to increase torque, use a larger driven pulley. Common starting points for 3D printers and CNC machines are 20 T–40 T on the drive side. This listing covers 30 T to 48 T — if you need a smaller drive pulley, check our other S3M listings.
Measure your motor or drive shaft diameter with a caliper before ordering. Common stepper motor shaft sizes are 5 mm and 6.35 mm (1/4 in); servo motors often use 8 mm, 10 mm, or 12 mm shafts. Select the bore that matches your shaft exactly — a loose bore will cause runout and vibration. If your shaft is between sizes, choose the smaller bore and have it reamed to fit, or select a keyway variant for a more secure fit.
A keyway is recommended when transmitting significant torque or when the pulley must not slip under reversing loads (e.g., CNC axes, robotic joints). For light-duty or low-torque applications such as 3D printer extruder drives, a set-screw bore without keyway is typically sufficient. Keyway width is determined by the shaft's existing keyway slot — match the keyway width to your shaft specification. Standard DIN 6885 keyway widths for common bore sizes: 8 mm bore → 3 mm key; 10–12 mm bore → 4 mm key; 14–15 mm bore → 5 mm key; 18–20 mm bore → 6 mm key; 25 mm bore → 8 mm key.
Yes — these pulleys are machined to the S3M tooth profile (3 mm pitch) and are designed for 10 mm wide S3M synchronous belts. They will not fit S2M (2 mm pitch), GT2, HTD, or other belt profiles. Always confirm your belt's pitch and width before ordering. If your belt is narrower or wider than 10 mm, the flange geometry may not center the belt correctly.
Aluminum alloy pulleys are well-suited for the torque levels produced by NEMA 17 and NEMA 23 stepper motors, as well as small servo motors commonly used in 3D printers, laser cutters, and light CNC machines. For heavy industrial drives with high continuous torque or shock loads, a steel pulley may be more appropriate. The BF flange design also helps distribute belt tension evenly across the tooth face, reducing localized stress.
Aluminum alloy naturally forms a thin oxide layer that provides moderate corrosion resistance in typical indoor environments. No lubrication is required or recommended for synchronous belt drives — oil or grease on the belt contact surface will degrade the belt and reduce grip. For humid or mildly corrosive environments, an anodized finish variant offers additional surface protection.
No. The S3M tooth profile is not interchangeable with GT2 (2 mm pitch), HTD 3M, or other belt profiles. Using a mismatched pulley and belt will result in poor meshing, increased noise, accelerated wear, and potential belt skipping under load. Always match the pulley profile and pitch to your belt specification.
