Custom Timing Pulleys: Options & Capabilities

Timing belts get a lot of attention, but the pulleys used in a timing drive are just as important for maximum performance. You might not find the pulley you need right off the shelf, but BRECOflex can help. Below, find a breakdown of different timing pulley customization options available so you can get the exact components you need, and the support necessary to get the design right from the start.

BRECOflex Custom Pulleys at a Glance

*More custom options are available per customer request.

Ordering custom pulleys from BRECOflex

There are several ways to order custom pulleys from BRECOflex, depending on the support you need.  

1. Submit a drawing: If you already have a technical drawing or model of the pulley you need, it can be submitted directly through our Custom Pulley RFQ form. Because drawings often have most of the necessary specifications included, this is often the easiest and most efficient way to order a custom pulley.  ‍
2. Fill out the RFQ form: Fill out the Custom Pulley RFQ form, which includes questions regarding common customizations. If a customization you need is not listed on the form, include the feature and relevant specifications in the “Additional Details” section of the form.  ‍
3. Call and Contact Us form: If you need additional support or have further questions, you can call BRECOflex directly at +1 (732) 460-9500 or complete the Contact Us form on our website. Our team can connect you with the resources necessary to design and purchase a custom pulley.

Re-ordering a custom pulley

Looking to re-order a custom pulley? Include the inventory number (BP00X000) printed on the side of the pulley when requesting a quote to get details for the exact same pulley. Can’t ID your pulley? Use our contact us form to get help with identifying your part for free.

Custom Timing Pulley Options

There are several pulley customization options, including flanges, keyways, set screws, bushing machining, materials, and more. Learn about the available customizations and the specifications needed to quote made-to-order pulleys below.

Pulley flanges

Flanges are raised edges attached to one or both sides of a pulley to keep timing belts tracking properly. All synchronous drives can benefit from flanged pulleys, but they are especially useful in vertical lift drives, designs with multiple pulleys, and systems with long belt spans.  

There are several options for choosing pulley flanges from BRECOflex:

• Rolled-on flanges: Attached by machining shoulders on the pulley sides that hold the flanges, which are then rolled and pressed securely on. Rolled-on flanges are standard for flanged pulleys AT15 pitch or lower. ‍
• Screwed-on flanges: Providing a stronger connection, screwed-on flanges are common in drives in demanding conditions where a belt may generate higher tracking forces, like drives using larger pitches, wider pulleys, higher belt tensions, or high-strength belts, like the move-series. Screwed on flanges are often thicker, requiring more space. They may not fit on all pulleys.   ‍
• Flange materials: Three pulley flange materials are available to meet specific application environment needs. Zinc-plated steel is standard for most pulleys, while aluminum and stainless steel (standard with stainless steel or Delrin pulleys) flanges are also available.

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Hubs

A pulley hub is a raised section at the center of the pulley that improves the connection between the pulley and the shaft. The additional hub material allows for greater torque capacity, eases maintenance and mounting, and improves design flexibility by allowing a wider range of bore and keyway sizes and different set screw locations.  

Although they can provide significant benefits, not every pulley has a hub. Pulleys without hubs are most commonly used in compact drives that have significant space or weight restrictions.  

BRECOflex can accommodate one hub, two symmetric or asymmetric hubs, and stepped hubs.  

Bores, counterbores, and pilot bores

One of the most important design features of a pulley is the diameter of the bore. It must be properly sized so the pulley can be mounted onto the shaft securely. The bore diameter is limited by the overall size of the pulley and if a keyway is needed. This prevents the pulley wall from being too thin, which could lead to it breaking under the load or torque the application requires.

In addition to the bore diameter, bore tolerance, which outlines the slight, allowable variation in the bore size, is another consideration. The bore tolerance ultimately dictates how the pulley is mounted to the shaft, and how tightly they fit together. The following bore tolerances are available from BRECOflex:

• H7: Standard bore tolerance ‍
• H6: Tightest bore tolerance ‍
• H8: Typical bore tolerance for keyless bushings ‍
• M6: Typical bore tolerance for press fit ‍
• Clr: Clearance of bore +0.1mm/-0.0mm

Counterbores can also be added to a pulley to reduce weight or provide clearance for shaft shoulders and other hardware. These recessed bores are precision machined directly into the pulley, and are also popular for designs that house bearings, pairs with bushings, or to allow fasteners to sit below the pulley face. BRECOflex can accommodate one, two symmetric, two asymmetric, or stepped counterbores.  

Basic pilot bores are available for pulleys that will be machined with finished bores, keyways, or set screws after purchasing.

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Self-tracking guide

Self-tracking guides are grooves machined on the tooth side of the pulley to pair with self-tracking timing belts. Using self-tracking components reduces belt movement and improves tracking without having to use flanges, making them popular for compact drives, or designs where flanges interfere with product transport, clearances, or general operation.

Self-tracking grooves are tapered, with the widest part at the top of the tooth, which gradually narrows at depth. There are three different self-tracking groove dimensions:

• K6: A 6.5mm wide* self-tracking groove with a 5mm depth**

• K10: A 10.5mm wide* self-tracking groove with a 7mm depth**

• K13: A 13.5mm wide* self-tracking groove with a 7.5mm depth**

The grooves can be machined centered on the pulley or offset, depending on the design needs. Imperial tracking guides can also be used, when needed.

_{*Groove width at top of tooth, +0.2/-0.0 mm tolerance}

_{** +0.1/-0.0 mm tolerance}

Keyways

A keyway is a slot that is machined into the bore of a pulley to match a keyed shaft, helping prevent it from slipping on the shaft. That extra reinforcement provided by the keyway promotes reliable torque transmission, even in demanding applications. Often, keyways are paired with set screws to further stabilize the pulley.

Keyway sizes are standardized and vary by bore size, but the alignment can vary. The default keyway alignment is on the tooth gap, with tooth alignment also available.  

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Set Screws

Threaded set screw holes can be added to the face or hub of BRECOflex pulleys to secure the pulley to a shaft and prevent rotation and axial movement. Any number of set screws can be added to the pulley, but the majority of applications need no more than two.  

The ideal location for a set screw hole varies with performance needs and design constraints.  

• Set screws on the pulley hub are easier to access and simplify maintenance, especially when timing belts are mounted. ‍
• Set screws on the pulley face are often used in applications with space constraints that restrict the use of hubs. However, they are more difficult to service when belts are mounted.

For high-torque loads, set screws alone might not provide enough strength to hold the pulley in place, so they are often paired with a keyway and keyed shaft.

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Bushing Machining

Bushings are popular components used in industrial drives that securely connect pulleys to shafts. The reliable attachment provided by bushings increases torque capacity and allows a single pulley design to fit multiple shaft diameters, which makes design, procurement, and replacement more flexible.  

Pulleys must be machined to accept a bushing attachment. BRECOflex offers custom machining for pulleys to match with either taper-lock (TL) bushings or quick detachable (QD) bushings.

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Materials and coatings

Several pulley material and coating options are available to improve application performance and environmental resistance:

• Aluminum: As a cost-effective and lightweight material, aluminum is the standard material for BRECOflex stock, modified stock, and custom pulleys. It offers moderate corrosion resistance, lower rotational inertia, and can reduce the amount of torque needed to accelerate and decelerate the pulley.  ‍
• Stainless steel: A durable, abrasion resistant material with excellent corrosion and chemical resistance compared to aluminum or carbon steel. Stainless steel pulleys are suitable for high power transmission, harsh-duty applications, and washdown environments and are commonly used in food, pharmaceutical, medical, and FDA-regulated applications.  ‍
• Steel: Ideal for high power transmission and applications that require high strength, durability, and abrasion resistance. Steel pulleys are substantially heavier than aluminum pulleys and are susceptible to corrosion unless an additional finish is applied.  ‍
• Delrin®/Acetal: A non-metallic pulley material for lower power transmission applications, light-duty conveying, or applications that require the distinct lightweight, non-metallic properties Delrin® pulleys offer. Though Delrin® pulleys have excellent resistance to many chemicals and moisture, they are not suitable for all chemicals, high loads, high temperatures, or abrasive environments.

BRECOflex offers a variety of coating and plating materials for pulleys to improve performance and longevity, including anodizing, hard anodizing, black oxide, zinc plating, chromate, and nickel plating. Additional coatings and finishes are available on request.  

For more details about material and coating options, read our Complete Guide to Pulley Materials and Finishes.  

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Reduced / Zero backlash tooth gap

Backlash is a measure of the motion lost in a drive as a belt tooth moves across the gap between the tooth and the pulley groove. While backlash is normal in a timing drive, some applications, especially those that require high levels of repeatability like reversible drives, need to minimize it.  

Reduced and zero backlash T and AT series pulleys are available from BRECOflex (including self-tracking versions), which can improve positional accuracy, repeatability and settling time in a drive system. With reduced backlash, tooth clearance is decreased, while zero backlash removes as much clearance as possible.

Bolt and mounting holes

Bolt and mounting holes are common pulley customizations, typically used to attach components to the pulley, mount the pulley on another part, or allow bolts to pass through into another component.  The holes are added to the side of the pulley, often in a bolt circle diameter.  

Options for custom pulley bolt and mounting holes include:

• Threaded or non-threaded holes ‍
• Through or blind holes

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Lightening holes and lightening grooves

Lightening holes and lightening grooves are modifications that reduce pulley weight and rotational inertia, which lowers the amount of torque needed to accelerate or decelerate the pulley.  

By reducing the load on shafts and bearings, lightening machining options make it so pulleys put less stress on other components, while simultaneously helping reduce drive noise and vibration. This is especially useful for larger pulleys or those made of heavy materials, like steel.

Choosing between lightening holes or lightening grooves depends on the application’s needs:

• Lightening holes are holes drilled through the pulley face and act as a simple way to reduce the weight of a pulley. This is a simple manufacturing process and removes the maximum amount of mass.  ‍
• Lightening grooves are pockets machined into the pulley, creating a recessed groove. It’s a more complex manufacturing process than lightening holes, but it provides more structural integrity and a closed surface to prevent contaminants from passing through the pulley.

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Snap ring groove

Grooves can be machined on a pulley bore or hub to accept a retaining or snap ring to hold the pulley on the shaft and prevent axial movement. Snap rings help maintain pulley alignment and simplify the installation process, but they must be paired with features like keyways, set screws, or bushings to prevent rotational movement and strengthen torque transmission.

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Get pulleys as unique as your application

When you get custom pulleys through BRECOflex, you’re not just getting the component you need. You have access to our in-house engineering experts for free design support, prototyping, machine-to-print capabilities, and easy procurement of compatible timing belts, clamps, and other accessories. Ready to get started? Contact us today!  

Additional Resources

• Free 3D Pulley Model Configuration Tool ‍
• Pulley Design Guide ‍
• Stock Pulleys  ‍
• Custom Pulley Request for Quote Form