A timing drive only works when the belt and pulley share exactly the same tooth profile and pitch. This guide compares the common timing belt profiles, explains how to read a belt code and lists what to specify when ordering standard or custom timing pulleys.

Timing Belt Profiles and Pitch

T and AT belts share the same pitch but use different tooth geometry, and HTD5M is not interchangeable with T5 or AT5 even though all three have a 5 mm pitch. Always match the profile name, not only the pitch.

Reading a Timing Belt Code

A code such as HTD5M-400-15 gives the profile (HTD5M), the pitch length (400 mm) and the width (15 mm). The number of teeth equals pitch length divided by pitch; here 400 / 5 = 80 teeth. Belts are available from about 180 to 1400 mm pitch length and 6.4 to 40 mm wide. See the timing belt range.

Specifying Timing Pulleys

• Profile and tooth count: standard pulleys are offered with 20, 30 and 40 teeth in each profile; other counts can be made to drawing.
• Belt width: the pulley face must suit the belt width, with or without flanges.
• Bore: pilot bore for customer machining, finished bore with keyway and set screws, or taper bore for a taper-lock bushing.
• Material: aluminum for light, low-inertia drives or C45 steel for higher torque.

See the timing pulley range and the taper bushing range for shaft mounting options.

Start with the Tooth Profile

The belt and pulley must use the same tooth profile and pitch. Similar-looking profiles are not automatically interchangeable. Customers should provide the belt marking, pulley drawing or a clearly identified standard.

Width, tooth count and center distance must then be considered together with the transmitted power, torque, speed and required service factor.

Pulley Geometry and Machining Details

Pulley inquiries should specify the tooth count, profile, width, bore, hub style, keyway, set-screw holes, flange requirements and material. Where a taper-bush or locking assembly is used, the interface must be clearly defined.

Machined bores and keyways should be based on the customer shaft and torque requirement rather than copied from an unrelated pulley size.

Tension and Alignment

Correct installation tension helps prevent tooth jumping, excessive vibration and premature bearing load. Over-tension can reduce belt and bearing life, while insufficient tension can affect positioning and tooth engagement.

Pulley alignment is equally important. Angular or parallel misalignment can produce edge wear and uneven load distribution.

Application Information

For a new system, customers should provide motor power, driving speed, driven speed, center distance, duty cycle, shock level, operating environment and any dimensional restrictions.

For replacement parts, the existing belt code and a dimensioned pulley drawing normally provide the fastest route to review.

Custom Timing Drive Components

TJOND can review custom timing pulleys, hubs, flanges and related machined parts based on drawings or samples. Final belt selection should be confirmed against the actual power and operating conditions.

Common Sources of Selection Error

One common mistake is to identify a timing belt only by width and approximate tooth spacing. Different profiles can look similar but use different tooth geometry. Another error is to select a pulley bore before confirming the hub diameter and keyway strength required by the transmitted torque.

Customers should also avoid changing pulley tooth count without checking belt length, center distance, wrap angle and motor speed. A small geometric change can affect both the speed ratio and belt engagement.

Replacement and Customization

For replacements, provide the full belt marking and clear photos of the pulley tooth form. For custom pulleys, a drawing should show the tooth specification, bore, keyway, hub, flanges, material, surface finish and quantity.

If the existing drive has suffered repeated belt damage, the inquiry should include the failure pattern. Edge wear, tooth shear and tensile-cord failure usually point to different root causes.

Information Customers Can Prepare

A useful timing drive inquiry includes the belt profile, pitch, width, pulley tooth counts, center distance, motor power, speeds, duty cycle and environment. Custom pulley drawings should define bore tolerance, keyway, hub and flange dimensions.

Where the customer is solving a repeated failure, photographs of the damaged belt and pulleys should be included. Failure evidence can reveal whether the primary issue is overload, tension, alignment, contamination or profile mismatch.

Frequently Asked Questions

Can I use a T5 belt on an HTD5M pulley?

No. Both have a 5 mm pitch, but the tooth shapes differ. Mixing profiles causes poor engagement, noise and rapid wear.

How do I find the number of teeth on a timing belt?

Divide the pitch length by the pitch. An AT10 belt with 1000 mm pitch length has 100 teeth.

When should I choose a V-belt instead of a timing belt?

V-belts rely on friction and allow some slip, which is acceptable for fans, pumps and general power transmission. Timing belts are used when speed ratio and position must stay synchronized. See V-belt pulleys.

Related Products

• Timing belts
• Timing pulleys
• Taper bushings
• V-belt pulleys

Have a drawing, a model number or only a worn sample? Send it with the operating conditions for a technical review and quotation.