V-ribbed Pulleys Information

V-ribbed pulleys or sheaves have a series of V-shaped ribs that mate with V-ribbed belts. They are used in numerous power transmission applications. V-ribbed belts are efficient, cost-effective, and designed for non-critical ratio drives. They usually have a triangular or trapezoidal cross-section and are reinforced with fiberglass, polyester, or steel.


V-ribbed pulleys are made from materials such as aluminum, brass, cast iron, steel, stainless steel, plastic, or zinc alloy. Both single groove and multiple groove devices are commonly available. There are several basic types of products. Standard V-ribbed pulleys have one or more grooves and are designed for general-purpose applications. Variable speed pulleys have faces or flanges that adjust axially to vary pitch diameter. Idler pulleys are used as belt tensioners and contain bearings that allow free rotation. Companion pulleys have ribbed webs for high strength-to-weight ratios. Multiple-size pulleys use step-down or cone configurations. Poly-V pulleys are used with mating belts for high-speed power transmission. Typically, both the section designation (H, J, L, M, or PK) and the number of ribs requires specification and belt-pulley matching.

Belt Size

Belt size is an important consideration when selecting V-ribbed pulleys. Both English and metric V-ribbed belts are available. English belts have numbered or letter designations and are measured in fractions of an inch (in). Belts with sizes such as 1/8 in., 3/16 in., and 1/4 in. indicate the width of the belt at the top. Belt types O, 3L, and Z are 3/8 in. or 0.44 in. wide. Other English belts include A and 4L (1/2 in. x 5/16 in.), B and 5L (21/32 in. x 13/32 in.), C (7/8 in. x 17/32 in.), D (1-1/4 in. x 3/4 in.), and E (1-1/2 in. x 29/32 in.). English belts with sizes such as 3V (3/8 in. x 5/16 in.), 4V (1/2 in. x 13/32 in.), 5V (5/8 in. x 17/32 in.) and 8V (1 in. x 29/32 in.) are also available. Metric size V-ribbed belts have numbered or lettered designations and are measured in millimeters (mm). Lettered metric belts include SPA (13 mm x 8 mm), SPB (17 mm x 11 mm), SPC (22 mm x 18 mm), SPZ (10 mm x 6 mm). Metric belts with a width of 5, 6, 8, 10, 13, 17, 20, 22, 25, or 32 mm are also available. V-ribbed pulleys differ in terms of pulley size, belt angle, belt width, operating temperature, shaft mounting, and pulley web style.


The most important dimensional specifications are pitch diameter, outside diameter, and bore diameter. Pitch or datum diameter determines the strength-to-weight ratio and, for variable or step pulleys, is a maximum amount. Outside diameter (OD) is measured to the outside of the pulley flanges. Bore diameter is specified for devices with a center hole for shaft mounting. Other mounting styles for V-ribbed pulleys use set screws, keyways, welds, quick-detach (QD) hubs, taper bushing, or simple bores. There are three pulley web styles: solid, spoke, and thin or ribbed. Solid pulley webs use belts with a uniform thickness along the radius. Spoke and thin or ribbed webs are designed for applications that require a reduction in pulley weight.

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