AT3 Timing Belts (3mm Modified Metric Trapezoidal)
AT3 timing belts are modified metric trapezoidal belts with a 3mm pitch, designed for precision small-servo drives, miniature automation, and compact European equipment. The AT-profile (Advanced Trapezoidal) features a wider tooth base and optimized tooth geometry compared to the standard T-profile, providing higher load capacity and reduced stress concentration at the tooth root. AT3 is the smallest pitch in the AT-profile family, which includes AT5, AT8, AT10, AT15, and AT20.
AT3 timing belts are manufactured primarily from polyurethane with steel wire tensile cords, making them ideal for precision positioning, low-particulate environments, and applications requiring near-zero stretch. They are available in both closed-loop and open-end (continuous roll) form. Texas Belting stocks AT3 timing belts for same-day shipping from Houston.
Pitch: 3mm (0.118")
Tooth profile: Modified trapezoidal (AT, wider tooth base than standard T-profile)
Profile family: AT-Profile (AT3, AT5, AT8, AT10, AT15, AT20)
Standard widths: 6, 10, 16mm
Primary material: Polyurethane with steel cord (standard); Kevlar cord available
Temperature range: -22°F to +176°F (-30°C to +80°C) standard
Formats: Closed-loop (welded endless) and open-end (continuous roll)
AT3 Part Number Decoder
AT3 timing belt part numbers follow the metric AT-profile convention. The number before the profile code indicates the pitch circumference in millimeters, and the number after the hyphen indicates the belt width in millimeters.
Standard Format: [Pitch Length]AT3-[Width]
| Part Number | Pitch Length | Width | Teeth | Construction |
|---|---|---|---|---|
| 150AT3-6 | 150mm | 6mm | 50 | Urethane, steel cord |
| 210AT3-10 | 210mm | 10mm | 70 | Urethane, steel cord |
| 330AT3-10 | 330mm | 10mm | 110 | Urethane, steel cord |
| 480AT3-16 | 480mm | 16mm | 160 | Urethane, steel cord |
| AT3-10 (open-end) | Per cut length | 10mm | Per length | Urethane, steel cord |
How to calculate teeth: Divide pitch length by 3. Example: 330 / 3 = 110 teeth. Some manufacturers reverse the format (for example, 10AT3-330). Open-end AT3 belts are sold by the meter and cut to any required length. Texas Belting can cross-reference AT3 part numbers from any manufacturer. Call 888-203-2358 or send us your part number for fast identification.
AT3 Width Guide
| Width (mm) | Width (Inches approx.) | Typical Applications |
|---|---|---|
| 6mm | 0.24" | Miniature servo drives, small instruments, encoders |
| 10mm | 0.39" | Most common AT3 width, small automation, pick-and-place |
| 16mm | 0.63" | Maximum standard AT3 width, heavier small-servo drives |
Custom widths may be available from open-end stock cut to width. Contact Texas Belting for non-standard width availability.
AT3 vs. Other 3mm Class Timing Belt Pitches
AT3 is one of several timing belt profiles available at or near the 3mm pitch. The table below compares AT3 to other small profiles to clarify differences and help you select the right belt.
| Profile | Pitch | Tooth Form | Load Capacity | Best For |
|---|---|---|---|---|
| AT3 | 3mm (0.118") | Modified trapezoidal (AT) | Light to moderate | Precision servo drives, European automation, high-load small drives |
| 3M (HTD) | 3mm (0.118") | Curvilinear (HTD) | Light | Small servo drives, 3D printers, CNC motion systems |
| GT2 (2mm) | 2mm (0.079") | Modified curvilinear (GT) | Very light | 3D printers, hobby CNC, miniature positioning |
| T2.5 | 2.5mm (0.098") | Trapezoidal (metric T) | Very light | European instruments, small sensors |
| MXL | 2.032mm (0.080") | Trapezoidal (ANSI) | Very light | US-standard miniature drives, encoders |
| T5 / AT5 | 5mm (0.197") | Trapezoidal / Modified trap. | Moderate | Next size up in T/AT family for heavier loads |
AT3 and 3M HTD both have a 3mm pitch but use different tooth profiles. AT3 is a modified trapezoidal with a wider tooth base, while 3M is curvilinear (rounded). They require different pulleys and are not interchangeable. AT3 provides higher load capacity per tooth than standard 3M HTD at the same pitch. For applications currently using 3M where more load capacity is needed, AT3 is a direct upgrade path (with new pulleys). See the Timing Belt Tooth Profiles Explained guide for visual comparisons.
AT3 Timing Belt Materials
AT3 timing belts are manufactured primarily from polyurethane. The AT-profile was designed around polyurethane construction from the start, and urethane is the standard material for all AT-profile belts.
Polyurethane with Steel Cord (Standard)
The standard AT3 construction uses a polyurethane body with steel wire tensile cord. Steel cord provides near-zero elongation (0.02%), making AT3 belts ideal for precision positioning and indexing applications. This construction is also available in FDA-compliant grades for food-contact use.
Polyurethane with Kevlar Cord
Kevlar (aramid) cord AT3 belts provide superior flex life around small pulleys. Use Kevlar cord when the drive uses small-diameter pulleys and belt fatigue life is a primary concern. Kevlar cord elongation is higher than steel (0.3 to 0.5%) but still very low compared to fiberglass.
| Property | Steel Cord (Standard) | Kevlar Cord |
|---|---|---|
| Elongation | 0.02% (near-zero) | 0.3 to 0.5% |
| Best for | Linear motion, indexing, precision positioning | Rotary drives with small pulleys, high flex life |
| Minimum pulley size | Larger (steel is stiffer) | Smaller (Kevlar flexes tighter) |
| Conductivity | Conductive | Non-conductive |
| Open-end available | Yes | Yes (less common) |
For more detail on urethane timing belt materials and cord options, see Urethane Timing Belts. For food-grade options, see Food Grade Timing Belts.
Common AT3 Timing Belt Applications
| Application | Why AT3 | Typical Width |
|---|---|---|
| Small servo drives (European automation) | Higher load than 3M HTD at same pitch. Precision positioning. | 10mm |
| Miniature linear motion | Open-end with steel cord for compact linear stages | 6 to 10mm |
| Medical and laboratory instruments | Low particulate urethane, precise motion, cleanroom compatible | 6 to 10mm |
| Semiconductor handling | Low outgassing, no particulate shedding, precision indexing | 6 to 10mm |
| Packaging machinery (small format) | Precise registration for label applicators and small feeders | 10mm |
| Optical and scanning equipment | Smooth, quiet, backlash-free motion for scan heads | 6mm |
| Robotics (compact drives) | Compact pitch with higher load capacity than GT2 or 3M | 10 to 16mm |
| Textile machinery (European) | Precision drives for bobbins, spindles, and feed mechanisms | 10mm |
For heavier loads at the AT-profile standard, step up to AT5 (5mm pitch) or AT8 (8mm pitch). For a full comparison of available profiles, see the Timing Belt Selection Guide.
AT3 Timing Belt Brands We Carry
| Brand | AT3 Product Lines | Notes |
|---|---|---|
| Gates | PowerGrip AT3 | Limited AT range. Stronger in HTD and Poly Chain. |
| Continental / ContiTech | Synchroflex AT3 | Industry leader in AT-profile urethane belts |
| Bando | Bando AT3 | High-quality Japanese manufacturing |
| Diesel Belting | Diesel AT3 | Cost-effective replacement option |
| Megadyne | Megalinear AT3 | Open-end and closed-loop urethane, strong AT-profile range |
Not sure which brand to specify? Request a quote or call 888-203-2358.
AT3 Timing Belt FAQs
Need AT3 Timing Belts?
Send us your part number, belt dimensions, or application details for fast identification and pricing.
