# of Flanges: Describes the number of flanges on a pulley. Most will have two flanges, to keep the belt from slipping, but some operations work best without any flanges. The rare product with only 1 flange is recommended for Genuine OEM replacement only.
Back Side Offset: The width from the center of the pulley to the backside edge of the hub or bore adapter.
Bearing ID: The inside diameter of the bearing used in the pulley. This is useful for determining if a bore adapter can be added, and if so, which sizes will fit.
Finish: The finishing material used to prevent rusting in steel or cast iron products. Zinc Plating and powder coat provide the best rust prevention.
Flange Angle: The angle of the flanges on flat idlers. Presented either as 90 degrees to reference perpendicular flanges, or in degrees away from perpendicular. Generally, wider angled flanges can decrease wear on your belt.
Flat Diameter: The diameter from side to side of the circle of the pulley. This is the diameter where your belt will ride.
Flat Width: The distance from side to side of the flat of the pulley. This is the width where your belt will ride.
Frontside Offset: The width from the center of the product to the front edge of the hub, bearing, or bore adapter.
Inside Diameter: The distance across the center hole, or bore, of the product. This dimension should match the diameter of your shaft or bolt.
Material: Describes what the product is made from. Plastic, aluminum, and diecast are softer, lighter, and do not rust. Steel and cast iron are meant for heavy-duty applications, but can rust in certain circumstances.
Material Thickness: Refers to the thickness of steel products only. This helps determine the overall sturdiness of the part. For Idler Pulleys, material thickness greater than 0.07” is considered Heavy Duty. For Drive Pulleys, thickness of 0.14” or greater is Heavy Duty.
Outside Diameter: The distance across the circle of the product, from outside edge to outside edge.
Stickout: The distance from the edge of the pulley’s flange to the edge of the bore adapter or hub. This is easiest to measure if the pulley is placed hub down on a flat surface. The stickout will be the space between the surface and the outside edge of the pulley. A negative stickout means that the pulley will lie flat on a surface with no gap.
Throughbore: Length of the bore, from one edge to the other. The Frontside Offset and Backside offset together equal the length of the throughbore.
Width: The distance from side to side of the pulley, across the area where the belt rides
For information on how to best measure your pulley, see our How to Measure Your Pulley page or contact us at [email protected].
