EP-T2.5-16 Aluminium Timing Pulley — 2.5mm Pitch for 6mm Belt Width

T2.5 METRIC TIMING PULLEY SERIES

EP-T2.5-16 Aluminium Timing Pulley — 2.5mm Pitch for 6mm Belt Width

Part Codes: 12T2.5–16 to 60T2.5–16 | Teeth: 12–60 | Pitch: 2.5mm | Belt Width: 6mm | Material: Aluminium

The EP-T2.5-16 series is a precision-machined aluminium timing pulley range covering 20 part numbers from 12 to 60 teeth, manufactured to the DIN 7721 T2.5 standard with a 2.5 mm pitch for use with 6 mm wide T2.5 synchronous timing belts. Lightweight, dimensionally accurate, and suited to high-speed, low-torque drives in servo motor systems, office automation, medical equipment, laboratory instruments, and compact precision machinery worldwide.

2. About Our T2.5-16 Aluminium Timing Pulley

The EP-T2.5-16 aluminium timing pulley is a miniature-format synchronous drive component designed for the highest shaft speed and lowest rotating inertia applications in the metric timing belt pulley family. The 2.5 mm pitch of the T2.5 series means that even the smallest 12-tooth pulley in this range has a pitch diameter of only 9.55 mm — small enough to mount directly on the output shaft of NEMA 17 or NEMA 11 stepper motors without any intermediate shaft adaptor, and small enough to fit within the compact enclosures of 3D printers, robotic end effectors, and miniature linear stages where the drive system competes for space with sensors, actuators, and structural elements. The aluminium alloy construction of the entire T2.5-16 series (unlike the steel or cast iron used in larger L and H series timing pulleys) reduces the rotational inertia of the pulley to the minimum achievable for the tooth count, which directly reduces the motor torque required for acceleration — a critical parameter in high-cycle servo applications where the drive must accelerate and decelerate hundreds of times per minute.

The –16 belt width code in the part number designates compatibility with the 6 mm wide T2.5 timing belt, which is the narrowest standard belt in the T2.5 family. A 6 mm wide T2.5 belt is used in the majority of miniature servo and stepper motor drive applications because it provides adequate tensile capacity for the low torque levels transmitted in these drives while minimising the axial space required for the belt drive on the motor shaft. Wider T2.5 belt variants (10 mm, 16 mm) are available for higher-torque applications, requiring pulleys with correspondingly wider flange-to-flange face widths. The EP-T2.5-16 series is specifically dimensioned for the 6 mm belt, with the F dimension (flange-to-flange face width) set at 9 mm for the smallest pulleys and 10 mm for 18T and above — both values providing the lateral containment needed for the 6 mm belt without adding unnecessary axial length to the drive assembly.

The type codes in this timing pulley series reflect the construction variation across the tooth count range. Types 1F (12T to 16T) and 6F (18T to 44T) are flanged designs where integral flanges at both ends of the toothed section retain the belt laterally. The small pitch diameter of 12T to 16T pulleys (9.55 mm to 12.73 mm) requires the 1F type construction with a different flange geometry than the larger 6F types. At 48T and 60T, the type designation becomes 6 (no F suffix), indicating a plain toothed section without flanges — at these larger diameters the belt has sufficient wrap angle and tension distribution to remain tracking without flanges, and removing the flanges simplifies manufacture and reduces the axial face width for space-critical designs. All types in the T2.5-16 series share the 16 mm hub length (L), providing a consistent axial envelope for the complete range.

3. Five Key Advantages of the EP-T2.5-16 Aluminium Timing Pulley

4. Working Principle of the T2.5 Timing Pulley System

The T2.5 aluminium timing pulley operates on the same positive meshing principle as all synchronous belt drive systems: the trapezoidal teeth machined into the pulley circumference engage the matching tooth spaces on the inner surface of the T2.5 timing belt, transmitting torque and motion with zero slip between driver and driven shafts. The T-profile tooth geometry is a flat-bottomed trapezoidal form with a 40° included tooth angle, defined by the DIN 7721 standard, which specifies the tooth pitch, height, width at the pitch line, and root radius for each metric T series. At 2.5 mm pitch the tooth dimensions are small: the tooth height is approximately 0.7 mm and the belt engagement depth at the pulley is correspondingly shallow. This small tooth height is adequate for the light loads and low belt tensions that characterise T2.5 timing pulley applications but would not withstand the high belt tensions and side loads of heavier industrial drives that require the H series or AT series tooth profiles with their deeper tooth geometry and larger root radii.

The aluminium alloy body of the pulley is machined by CNC gear hobbing to produce the tooth profile, followed by turning to produce the hub, flanges, and bore. The pilot bore is the initial bore state as machined — in the T2.5-16 series, most sizes from 12T to 44T are supplied with a pilot bore (shown as – in the d column), meaning the hub bore is machined to a small initial diameter that the user enlarges to the required shaft size. This pilot bore approach allows a single pulley part number to be adapted to multiple shaft diameters in the field, which is particularly useful for the diverse shaft sizes found across the stepper motor and servo motor products used with T2.5 drives in 3D printing, robotics, and automation. The 48T and 60T sizes are exceptions: the 60T size is supplied with an 8 mm pre-machined bore, and the 48T with a plain bore, reflecting the larger hub wall thickness available at these tooth counts where machining to a defined bore is practical without compromising structural integrity at the hub wall.

Correct belt pre-tension is more critical in T2.5 timing pulley drives than in larger-pitch belt drives because the small tooth height of the T2.5 profile provides a shallow engagement depth that is more susceptible to tooth jumping under overload or under-tensioned conditions. When the T2.5 timing belt is correctly pre-tensioned, the static tension on the slack side of the drive is sufficient to maintain full tooth engagement throughout the wrap arc of the smaller pulley even under the dynamic loads of rapid acceleration. Under-tensioned T2.5 drives are the most common cause of early belt failure in miniature drive applications — the belt teeth jump over the pulley teeth under the shock of rapid acceleration, damaging both the belt teeth and the pulley tooth tips in a failure mode that requires replacement of both components. Machine designers and maintenance technicians working with T2.5 aluminium timing pulleys should verify that the specified minimum belt tension is achievable with the tensioner or centre distance adjustment available in their machine design before finalising the drive layout.

5. Materials and Manufacturing Quality

The aluminium alloy used in the EP-T2.5-16 timing pulley series is a free-machining aluminium alloy equivalent to 6061-T6 or 2024-T4, selected for its combination of machinability, strength, and surface treatment compatibility. The alloy provides a yield strength of approximately 275–324 MPa (for 6061-T6), which is more than adequate for the tooth root bending stress levels encountered in T2.5 drive applications where the transmitted torque is inherently limited by the small belt width and shallow tooth engagement depth. The machining quality of the tooth profile is critical for the T2.5 series because the small tooth height (approximately 0.7 mm above the outside diameter) means that any tooth tip rounding, chatter marks, or pitch error has a proportionally larger effect on belt engagement quality than in larger-pitch pulleys where the tooth geometry has more dimensional margin. The YHK CNC gear hobbing process for the T2.5 aluminium timing pulley achieves tooth profile accuracy consistent with DIN 7 gear quality class or better, with pitch deviation controlled to within ±0.01 mm and tooth profile form error within the DIN 7721 tolerance band for the T2.5 profile.

After CNC machining, all aluminium T2.5 timing pulleys in the T2.5-16 series receive a deburring and cleaning process to remove the sharp edges and aluminium swarf that would otherwise be present at the tooth tips and bore entry chamfer from the machining operation. The bore of pilot bore variants is finished to a smooth internal surface to facilitate the bore enlargement operation that the end user performs with a drill or reamer in the field. For pulleys supplied with a pre-machined bore (the 60T size with 8 mm bore), the bore is precision-reamed to H7 tolerance to provide a close-running fit with standard shafts at the nominal bore diameter. The external surfaces of the pulley — the hub outside diameter, flange faces, and tooth tips — are left in the natural machined aluminium condition as standard, appearing as bright silver. For applications where anodising, hard anodising, or chemical conversion coating is required for corrosion protection or cleanroom suitability, these surface treatments are available as custom options and must be specified at the time of order as they change the surface finish and slightly alter the tooth tip and bore dimensions.

6. Regulatory and Standards Compliance

The T2.5 metric timing belt pulley standard is defined by DIN 7721 Part 1 (Zahnriemenscheiben — Abmessungen), the German standard for metric trapezoidal timing belt pulleys. This standard specifies the tooth pitch, tooth profile geometry, and the dimensional envelope for each belt width code, and it is the reference used by all global manufacturers of T2.5 timing pulleys and belts. The EP-T2.5-16 series complies with the DIN 7721 dimensional requirements for the T2.5 pitch and 6 mm belt width, ensuring meshing compatibility with DIN 7721-compliant T2.5 timing belts from all major global belt manufacturers.

For machinery incorporating T2.5 timing pulleys and sold into the European Union, the EU Machinery Directive 2006/42/EC (to be superseded by the EU Machinery Regulation 2023/1230 from January 2027) requires that the machine builder document the power transmission component specifications, including the pulley material, tooth standard, and design load, as part of the CE marking technical file. The EP-T2.5-16 aluminium timing pulleys are manufactured under ISO 9001:2015 quality management, and material certificates and dimensional inspection records are available to support CE marking technical file preparation for European OEM machine builders. In North America, OSHA 29 CFR 1910.219 requires guarding of power transmission components, which applies to T2.5 timing pulley belt drives as to all to all rotating power transmission equipment. In Japan, the equivalent metric timing pulley standard is JIS B 1856, which aligns with DIN 7721 for the T-profile metric series, making the EP-T2.5-16 pulleys compatible with T2.5 timing belts and machinery designed to Japanese standards. For the global 3D printer aftermarket and hobbyist CNC market, the EP-T2.5-16 pulleys conform to the de facto community standard for T2.5 pulleys established through the widespread use of this tooth form in RepRap-derived and commercial 3D printer designs, where the 20T2.5 and 36T2.5 sizes are the most frequently specified pulleys for X and Y axis stepper motor drives.

7. Application Scenarios

The T2.5 aluminium timing pulley is the standard synchronous drive component for compact, high-speed, low-torque synchronous belt drives across a diverse range of precision equipment categories. The following application areas represent the primary market segments for the EP-T2.5-16 series.

8. About Us

Our timing pulley manufacturing group produces a comprehensive timing pulley range of metric and inch-pitch synchronous belt pulleys including the full DIN 7721 T-series (T2.5, T5, T10, T20), AT-series (AT5, AT10, AT20), HTD-series (3M, 5M, 8M, 14M), GT2/GT3 series, and the ANSI inch-pitch series (MXL, XL, L, H, XH, XXH). Pulleys are manufactured in aluminium alloy, steel, and cast iron, with surface treatment options including natural machined, anodised, hard anodised, and chemical conversion coating. The production facility operates CNC gear hobbing machines, precision turning centres, and CMM inspection equipment under ISO 9001:2015 quality management. We supply global OEM machine builders, distributors, and aftermarket buyers for 3D printing, robotics, automation, medical equipment, and industrial machinery applications. Dimensional drawings, material certificates, DIN 7721 conformance documentation, and bore dimension drawings are available for all standard range items. Custom T2.5 pulleys with non-standard tooth counts, wide belt widths, custom bore sizes, or special surface treatments are produced to drawing. Contact our technical team for product selection guidance, custom specification enquiries, or volume pricing.

9. Related Products — Complete T2.5 Synchronous Drive System

The EP-T2.5-16 aluminium timing pulley is the core component of a complete T2.5 synchronous belt drive. We supply the complementary components needed to build a complete T2.5 drive system from a single supplier, ensuring dimensional compatibility across all drive elements.

ISO 5294 Timing Pulleys — L and H Series (Straight Bore)

For applications requiring higher torque than the T2.5 series can provide, our L series and H series straight bore timing pulleys offer the next steps up in belt pitch (9.525 mm L and 12.7 mm H) with significantly higher belt load capacity. When a T2.5 drive reaches its power limit — which occurs relatively quickly as the application grows beyond miniature-scale automation — the L series aluminium timing pulley in the same configuration provides approximately 14 times the torque capacity for the same drive speed, at the cost of a proportionally larger pitch diameter. Our range covers the complete transition from T2.5 miniature drives through to large H series industrial drives in a consistent product family with matched documentation standards.

V-Belt Pulleys

Our V-belt pulleys complement the T2.5 aluminium timing pulley range for machines that use both synchronous belt drives (for precision positioning axes) and V-belt drives (for auxiliary loads such as cooling fans or hydraulic pumps). Specifying both pulley types from the same supplier provides consistent quality documentation and surface finish standards across the full drive train of a multi-drive machine, simplifying the technical file for CE marking and reducing supplier management overhead for global OEM machine builders who source mechanical components through centralised procurement.

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