Bar Stock Timing Pulleys

What are bar stock timing pulleys?

Bar stock timing pulleys are long, solid bars with timing belt teeth machined along their full length. Instead of buying a finished pulley, the bar is cut to the width needed and machined to create a custom pulley, with the bore, hub, and fixing chosen to suit the application. They are supplied unmachined, so engineers and machine builders can produce exactly the pulley they need for bespoke belt drives, prototypes, and repairs.

A standard bar stock timing pulley is made up of:

• A solid aluminium bar, which is light, easy to machine, and resists corrosion
• Precision-cut teeth running along the full length of the bar, to suit one belt profile and pitch
• A set number of teeth, which fixes the pulley’s diameter and speed ratio
• A working length, which is the usable toothed length of the bar.

The unmachined design is what makes bar stock so versatile.

• The bar can be cut into several pulleys of different widths, or used as one long pulley for wide belts or rollers.
• The bore, keyway, set screws, hubs, and flange recesses are all machined by the customer, so the finished pulley fits the shaft and machine exactly.

Bar stock timing pulleys are described by their tooth profile, number of teeth, pitch, and working length.

Why are bar stock timing pulleys essential?

Bar stock timing pulleys give engineers complete freedom to make a pulley that is not available off the shelf. A finished pulley comes with a fixed width, bore, and hub, while bar stock lets the bore size, length, and fixing method be chosen to suit the job.

This makes bar stock ideal for special machines, one-off builds, and urgent repairs, where waiting for a custom pulley to be made would hold up production. Because a single bar can make several pulleys, it is also a cost-effective way to keep stock for maintenance and short production runs.

Typical applications include:

• Bespoke and special-purpose machinery
• Automation and robotics
• Prototypes and development projects
• Packaging and labelling machinery
• Linear drives and positioning systems
• Conveyor and transfer systems
• Machine repair and maintenance workshops
• Toothed rollers and wide belt drives

The main types of bar stock timing pulleys

• T profile bar stock - Bars with trapezoidal teeth in metric pitches, such as T2.5, T5, and T10, for general automation and precision drives.
• AT profile bar stock - Bars for AT belts, such as AT5 and AT10, which have larger, stronger teeth than T profile belts and carry higher loads with greater accuracy.
• Imperial profile bar stock - Bars with trapezoidal teeth in inch pitches, such as MXL, XL, and L, for imperial and older machinery.
• Curvilinear profile bar stock - Bars with rounded teeth, such as 3M, for belts with curved tooth profiles that run quietly and carry high loads.
• Short and long working lengths - Bars are made in a range of working lengths, typically from around 50mm up to 160mm, to suit the number and width of pulleys needed.

How to choose the right bar stock timing pulleys?

• Profile and pitch - Choose a bar with the same tooth profile and pitch as the belt. Profiles with the same pitch, such as T5 and AT5, are not interchangeable.
• Number of teeth - Choose the number of teeth to give the speed ratio and pulley diameter needed. More teeth give a larger diameter.
• Working length - Choose a bar long enough for the pulley width, plus any flanges, hubs, and material lost in cutting.
• Bore size - Check the bar is large enough to machine the bore and keyway you need, with enough wall left between the bore and the tooth roots.
• Flanges - Plan how the belt will be guided, as bar stock does not come with flanges. Flanges are usually fitted to at least one pulley in the drive.

Essential references and specialised ranges

How the numbering works:

Bar stock timing pulleys are usually referenced by the tooth profile and the number of teeth. The working length is given in the product details. For example:

T5 x 32 = T5 profile, 5mm pitch, 32 teeth

AT5 x 44 = AT5 profile, 5mm pitch, 44 teeth

L x 19 = L profile, 0.375 inch pitch, 19 teeth

MXL x 11 = MXL profile, 0.08 inch pitch, 11 teeth

Suffixes:

T = trapezoidal metric profile, followed by the pitch in mm

AT = heavy-duty trapezoidal metric profile, followed by the pitch in mm

M = curvilinear metric profile, after the pitch in mm

Suffix codes vary between manufacturers, so check the supplier’s catalogue for the exact meaning.

FAQ - All you need to know about bar stock timing pulleys

What is bar stock used for?

Bar stock is used to make custom timing pulleys. The bar is cut to width and machined to the bore, hub, and fixing needed, which is ideal for special sizes, prototypes, and repairs.

Can I make more than one pulley from a bar?

Yes. A bar can be cut into several pulleys, as long as each is wide enough for the belt and allows for flanges and cutting.

What is the working length?

The working length is the usable toothed length of the bar. It is the maximum amount of material available for making pulleys.

Can I use a T5 belt with AT5 bar stock?

No. T5 and AT5 have the same pitch but different tooth shapes, so the belt will not mesh correctly. Always match the bar to the belt profile.

What material is bar stock made from?

Most bar stock timing pulleys are made from aluminium, which is light, strong, corrosion-resistant, and quick to machine.

How do I identify the bar stock I need?

Check the profile and pitch printed on the belt, then count the teeth on the existing pulley. If the belt cannot be read, measure the distance between teeth and check the tooth shape.

How can I tell if a pulley made from bar stock needs replacing?

Warning signs include:

• Worn, hooked, or polished teeth
• The belt skipping teeth or jumping under load
• Rapid belt wear or wear on one edge of the belt
• Increased noise or whining from the drive
• A loose pulley, worn bore, or damaged keyway
• Burrs or damage to the tooth tips