Trapezoidal Timing Pulleys (XL, L, H)
Profile: Trapezoidal (angled tooth form)
Pitches: XL (1/5" / 5.08mm), L (3/8" / 9.525mm), H (1/2" / 12.7mm)
Mounting: Pilot bore with set screw and keyway (standard), QD on larger H pulleys
Materials: Aluminum (XL, small L), steel, cast iron (larger L, H)
Brands: Gates (PowerGrip)
In Stock: Same-day shipping from Houston
Trapezoidal timing pulleys are the drive wheels for XL, L, and H timing belts. The trapezoidal tooth form is the original timing belt profile, developed before the curvilinear HTD and GT designs. The teeth have straight, angled sides (like a trapezoid) that mesh with matching teeth on the belt for positive, no-slip power transmission.
While newer curvilinear profiles like HTD and GT offer higher load capacity per tooth, trapezoidal pulleys remain the standard for millions of existing drives in light to medium duty industrial, OEM, and instrumentation applications. They are simple, proven, widely available, and cost-effective. Texas Belting stocks trapezoidal pulleys in all three standard pitches to match every trapezoidal timing belt we carry.
Trapezoidal Pulleys by Pitch
| Pitch | Details |
|---|---|
| XL | Pitch: 1/5" (5.08mm). Load: Light. Tooth counts: 10 to 60+. Belt widths: 1/4", 3/8", 1/2", 3/4". Mount: Pilot bore with set screw. Material: Aluminum (standard). Use: The lightest trapezoidal pitch. Instruments, office machines, small OEM, business equipment, printers, plotters, small automation. |
| L | Pitch: 3/8" (9.525mm). Load: Medium. Tooth counts: 10 to 60+. Belt widths: 1/2", 3/4", 1", 1-1/2", 2". Mount: Pilot bore or set screw (small); QD on larger sizes. Material: Aluminum or steel. Use: The most common trapezoidal pitch. Light industrial drives, packaging, food equipment, textile machines, general OEM. |
| H | Pitch: 1/2" (12.7mm). Load: Medium to heavy. Tooth counts: 14 to 120+. Belt widths: 3/4", 1", 1-1/2", 2", 3". Mount: Pilot bore, set screw, or QD on larger sizes. Material: Steel or cast iron. Use: The heaviest standard trapezoidal pitch. Machine tools, compressors, large conveyors, industrial pumps, heavy OEM equipment. |
Part Number Decoder
Trapezoidal timing pulley part numbers follow a simple format: tooth count, pitch letter, and belt width in hundredths of an inch.
| Example | What It Means |
|---|---|
| 16XL025 | 16 teeth, XL pitch, 1/4" (0.25") belt width. |
| 24XL037 | 24 teeth, XL pitch, 3/8" (0.37") belt width. |
| 20L050 | 20 teeth, L pitch, 1/2" (0.50") belt width. |
| 30L100 | 30 teeth, L pitch, 1" (1.00") belt width. |
| 24H100 | 24 teeth, H pitch, 1" (1.00") belt width. |
| 48H200 | 48 teeth, H pitch, 2" (2.00") belt width. |
This format is consistent across most manufacturers, making cross-referencing straightforward. The bore size is specified separately when ordering. Send us any part number and we will confirm availability.
Mounting Options
| Mount Type | Details |
|---|---|
| Pilot Bore / Set Screw | The standard mount for XL and L pulleys. Hub is rough-bored and finish-machined to the shaft diameter. Secured with set screw and keyway. Simple, low cost. Most common for trapezoidal pulleys. |
| QD Bushing | Available on larger L and H pulleys. Removable tapered bushing for fast install/removal and shaft flexibility. Preferred for industrial H-pitch applications where maintenance speed matters. |
| Plain Bore (No Keyway) | Some small XL pulleys are available with a plain bore (no keyway) for press-fit or adhesive mounting on very light duty applications. Not recommended for power transmission. |
Trapezoidal vs. Curvilinear (HTD/GT)
Trapezoidal and curvilinear timing pulleys serve the same basic function but differ in tooth geometry and performance characteristics.
| Feature | Details |
|---|---|
| Trapezoidal Tooth | Straight-sided, angled tooth. The original timing belt profile. Load concentrated at the tooth tip. Lower capacity per tooth than curvilinear profiles. |
| HTD/GT Tooth | Curved (semicircular or modified curvilinear). Load distributed across the tooth face. Higher capacity per tooth. Quieter operation. |
| When to Use Trapezoidal | Replacing existing trapezoidal drives. Light to medium duty. Cost-sensitive OEM. Applications where the installed base uses XL, L, or H profiles. Simple, proven, widely available. |
| When to Use HTD/GT | New designs requiring higher torque capacity. Heavy industrial applications. Precision positioning where backlash matters. Upgrading from trapezoidal for more power in the same space. |
| Compatibility | Trapezoidal belts require trapezoidal pulleys. HTD belts require HTD sprockets. GT belts require GT sprockets. Never mix profile families. |
Common Applications
| Application | Typical Pulley |
|---|---|
| Office/business equipment | XL pulleys. 10 to 24 teeth. Aluminum. Printers, copiers, plotters, scanners. |
| Small automation | XL pulleys. 16 to 36 teeth. Aluminum. Conveyors, feeders, pick-and-place. |
| Packaging machines | L pulleys. 16 to 40 teeth. Steel or aluminum. Feed drives, indexing. |
| Textile machines | L pulleys. 20 to 48 teeth. Steel. Loom drives, thread handling. |
| Food equipment | L pulleys. 16 to 36 teeth. Stainless or aluminum. Conveyor and processing drives. |
| Machine tools | H pulleys. 18 to 72 teeth. Steel or cast iron. Spindle drives, feed mechanisms. |
| Compressors/pumps | H pulleys. 24 to 60 teeth. Steel or cast iron. QD mount on larger sizes. |
| Large conveyors | H pulleys. 36 to 120 teeth. Cast iron. QD mount. Heavy industrial. |
Brands We Carry
| Brand | Products |
|---|---|
| Gates | PowerGrip trapezoidal timing pulleys in XL, L, and H. Pilot bore and QD mount. Aluminum and steel. Full tooth count and width range. |
Trapezoidal pulley part numbers are standardized across manufacturers, making cross-referencing straightforward. Send us any part number and we will confirm availability.
Related Pages
Frequently Asked Questions
What is a trapezoidal timing pulley?
A trapezoidal timing pulley is a toothed drive wheel with straight-sided, angled teeth (shaped like a trapezoid) that mesh with a matching trapezoidal timing belt. It is the original timing belt tooth profile, predating the curvilinear HTD and GT designs. Trapezoidal pulleys are available in three standard pitches: XL (1/5"), L (3/8"), and H (1/2").
What is the difference between XL, L, and H pulleys?
The letters indicate the pitch (tooth spacing): XL is 1/5" (5.08mm), L is 3/8" (9.525mm), and H is 1/2" (12.7mm). Larger pitch means larger teeth and higher load capacity. XL is for light duty, L is for medium duty, and H is for medium to heavy duty applications. Each pitch requires a belt with the matching pitch designation.
Can I use an HTD sprocket with an XL or L belt?
No. Although XL (5.08mm) and HTD 5M (5mm) have similar pitch dimensions, the tooth shapes are completely different. Trapezoidal teeth are straight-sided and angled. HTD teeth are semicircular. They will not mesh correctly. The same applies to L vs. 8M and H vs. 14M. Always match the pulley profile to the belt profile exactly. See our Tooth Profiles guide for visual comparison.
How do I read a trapezoidal pulley part number?
The format is: tooth count + pitch letter + belt width in hundredths of an inch. For example, "24XL037" means 24 teeth, XL pitch, 3/8" (0.37") belt width. "30L100" means 30 teeth, L pitch, 1" (1.00") belt width. This format is consistent across most manufacturers.
Should I upgrade from trapezoidal to HTD or GT?
If your existing trapezoidal drive is working well and meeting performance requirements, there is no need to upgrade. Trapezoidal drives are simple, proven, and cost-effective. Consider upgrading to HTD or GT if you need more torque capacity in the same space, lower noise, better positioning accuracy, or if you are designing a new drive from scratch. An upgrade requires replacing both the belt and all pulleys since the profiles are not interchangeable.
What mounting options are available?
Most XL and L pulleys use pilot bore with set screw and keyway. Larger L and H pulleys may accept QD bushings for faster installation and shaft flexibility. Some small XL pulleys are available with plain bore for press-fit mounting on very light applications.
Do trapezoidal pulleys need flanges?
Flanges help keep the belt tracking straight on the pulley. Most standard trapezoidal pulleys include flanges on one or both sides. On a two-pulley drive, the general rule is to flange the smaller pulley (or both). If your pulley does not include flanges, aftermarket flanges are available for most sizes.
Can Texas Belting cross-reference trapezoidal pulley part numbers?
Yes. Trapezoidal part numbers are largely standardized across manufacturers, so cross-referencing is straightforward. Send us the part number and we will confirm the equivalent in stock, or call 888-203-2358.
