Synchronous-drive timing pulleys are defined first by tooth pitch (inch-based XL/L/H or metric T/AT/HTD/STD), then by bore style, tooth count, and belt-width envelope, and finally by the matched timing belt series — a 1:1 pitch match between pulley and belt is the hard engineering rule [S1][S7].
Classifications also break out by function inside the drive train: drive (power-transmitting) pulleys, tensioner pulleys (typically 55–60 mm OD, 18–29 mm width in the automotive replacement channel), and idler/deflection pulleys in the 60 mm OD / 24 mm width class [S2][S6][S8].
Inch-Series Pitch Family: MXL, XL, L, H, XH, XXH
The classic inch pitch family — MXL (0.080 in), XL (0.200 in / 1/5 in), L (3/8 in), H (1/2 in), XH (7/8 in), and XXH — covers light office machinery through heavy industrial drives, with trapezoidal (HTD-adjacent) tooth forms sitting alongside the curvilinear HTD/STPD profiles that succeeded them [S1].
MISUMI's 2026 catalog surfaces the full inch lineup at fixed belt widths of 0.13 in (1/8 in), 0.19 in (3/16 in), 0.25 in (1/4 in), 0.38 in (3/8 in), 0.50 in (1/2 in), 0.75 in (3/4 in), 1.00 in, 1.50 in (1-1/2 in), and 2.00 in — a 9-step width ladder that maps directly to standard belt stock [S4]. For light loads at low torque (printers, small instruments, low-cost hobby CNC), MXL and XL remain the default because the small pitch lets more teeth mesh per degree of rotation, smoothing torque transmission [S1][S4].
Metric Pitch Family: T2.5, T5, T10, AT5, AT10, HTD 3M/5M/8M/14M
Metric pitches are catalogued as T-series (T2.5, T5, T10) for trapezoidal tooth form, AT5 / AT10 for the high-torque trapezoidal upgrade, and the HTD curvilinear 3M / 5M / 8M / 14M family plus the 2026-typical S2M / S3M / S5M / S8M / S14M PowerGrip GT3 series, with MR2/MR3/MR5 modifiers specifically for Gates PowerGrip GT3 compatibility [S4].
Curvilinear HTD/STPD/GT profiles carry load on the tooth flank rather than the tip, which is why AT5/AT10 and the S-series have displaced classical T5/T10 in most new European and Asian OEM panels since the late 2010s [S4]. For drives that exceed roughly 1–2 kW at shaft speeds below 1500 rpm, AT10 or 14M is the routine starting point, while 3M and 5M remain common in small automation, packaging, and instrumented motion axes [S4].
Bore and Mounting Class: Straight, Taper, and Pilot-Bore
Bore type is the second decision axis after pitch: pilot-bore (plain) for light/light-tolerance applications, straight finished-bore for direct shaft mounting, and taper-bore (Taper-Lock / QD bushing system) for shaft diameters that may change or that need a positive shrink-fit on the shaft [S1][S7].
Chinese OEM data shows that one in-house machining line can stock both straight-bore and taper-bore variants across MXL, XL, L, H, AT, and HTD profiles, with custom non-standard bores, flanges, and modified hubs available on drawing — a footprint typical of a flexible Tier-2 timing-pulley shop [S7]. For a given pitch and tooth count, the bore is normally undersized relative to the pulley OD; a 60-tooth XL pulley and a 60-tooth L pulley share the tooth count but their pitch diameters (and therefore recommended bore windows) differ by roughly a factor of two because the pitch itself steps from 0.200 in to 3/8 in [S1][S4].
Drive vs. Tensioner vs. Idler/Deflection Pulley
Inside a synchronous belt loop, three functional classes coexist: drive (power-transmitting) pulleys, tensioner pulleys (spring-loaded, maintain belt wrap and pre-load), and idler/deflection pulleys (redirect the belt path, no torque transmission) [S2][S5][S6].
Real 2026 replacement data shows a tight OD/width envelope: NIPPARTS J1140305 for KIA at 58 mm OD / 29 mm width, BLUE PRINT ADC47655 for Chrysler/Dodge/Mitsubishi at 0.760 kg and 18 mm width class, AUTEX 654891 for Mitsubishi MN137248 at 60 mm OD / 24 mm width, and PROFIT 1014-0027 for Hyundai/Kia/Mitsubishi at 55 mm OD / 18 mm width — a 55–60 mm OD / 18–29 mm band that recurs across Asian passenger-car replacement SKUs [S2][S5][S6][S8]. Drive pulleys, by contrast, are sized to the load and have no fixed envelope — a 14M-240S drive pulley can run several hundred millimetres in pitch diameter and kilograms in mass [S4].
Tooth Count, Pitch Diameter, and the Selection Calculation
Pitch diameter (PD) is calculated as PD = pitch × teeth / π, and for metric pitches expressed in millimetres, PD = (pitch × teeth) / π, with 14M-60S therefore landing at 14 × 60 / π ≈ 267.4 mm PD; for 8M-30S the result is 8 × 30 / π ≈ 76.4 mm PD [S1][S4].
Belt speed scales linearly with PD and shaft speed: v = π × PD × n / 60, so a 14M-60S at 1500 rpm carries roughly 21 m/s of belt linear speed — a level at which dynamic balance and bore concentricity become non-negotiable, while the same 1500 rpm on a 3M-20S (PD ≈ 19.1 mm) gives only 1.5 m/s and tolerates much looser machining tolerances [S1][S4]. General selection practice also keeps at least 6 teeth in mesh for inch profiles and roughly 7–10 for HTD/STPD to avoid tooth jump and ratcheting under transient load [S1].
Material, Finish, and Custom-Build Class
Materials in the 2026 catalog range from C45 carbon steel and aluminium 6061/6082 for general drives to hardened alloy steels for high-cycle, high-load HTD/STPD applications, with surface treatments such as black oxidation, zinc plating, anodising, and electroless nickel applied for corrosion resistance [S3][S7].
One Chinese supplier (Wuxi-based, ISO 9001-certified, founded 2015) lists a black timing-pulley SKU in the USD 10–15 FOB tier at 100+ piece order quantity, shipped with T/T, L/C, or Western Union terms — a price band that signals commodity-grade carbon-steel construction rather than hardened alloy [S3]. Custom-bore and custom-flange machining is offered on drawing or sample across the same supplier base, including non-standard bores, special flanges, and modified hubs for OEM and one-off replacement needs [S7].
Standards, Pitch Equivalence, and What to Verify
Tooth-geometry references for the inch family trace back to the historical MXL/XL/L/H trapezoidal standards and the ISO 5295 / ISO 5294 contour-and-pitch family for the metric side, with the HTD/STPD/GT curvilinear profiles governed by Gates' PowerGrip specification and the equivalent RPP/HPP profiles from ContiTech and Optibelt [S1][S4].
When matching pulleys to a timing belt the three non-negotiable checks are pitch (mm or in), tooth profile (trapezoidal vs. curvilinear — AT and HTD are NOT interchangeable), and belt width, with bore diameter and keyway specified separately [S1][S4][S7]. A pragmatic next step is to lock the pitch and profile first, then size the pulley by tooth count against the desired speed ratio and the driver rpm, then add the belt-width code (037, 050, 075, 100, 150, 200 for 14M, and 006/009/015/020/025/030 for 8M as catalogued by MISUMI in 2026) [S4].
Spec-level background on the components involved: pressure transmitter.
See also our earlier report, Loop Impedance Tester 2026: Spec Map, Variants, and Buying Criteria.