The Martin type BS sprocket, also known as a bored-to-size sprocket, with hardened teeth, includes two setscrews and a keyway, and is suitable for use with the series 40 chain with 1/2" pitch. This sprocket has been adapted for installation on the shaft without additional components. Made from high carbon steel, it has high strength and durability.

Type BS sprockets have a hub extension on one side to provide stability and allow for the use of a full-depth keyway and two standard setscrews to attach the sprocket onto a shaft.

The options for this class of sprocket are: number of teeth from 9 to 30; outside diameter from 1.670 to 5.060"; length through bore from 7/8 to 1.00"; and approximate weight from 0.16 to 2.70 lb. The chain row width is 0.284" nominal. The keyway is on the centerline of the tooth. The following exceptions are present: the 9- through 15-tooth option with 1/2" shaft have no keyway and use two (2) 1/4" setscrews at 90 degrees to each other. With this series of sprockets, the hub diameters will vary to suit different bore sizes. All Martin sprockets meet or exceed ANSI standards.

A sprocket is a wheel with teeth around the perimeter that meshes with a chain, track, or other perforated or indented material. Unlike gears that mesh with another gear, sprockets mesh with a chain, which then interacts with another sprocket. Gears can be used to transmit power around a corner, based on how they fit together. Sprockets with chains only work in straight lines. Some common benefits of chain-drive systems include minimal slippage, a fixed ratio between rotating shafts, and versatility with many different chain attachments and sprocket material selections. An example of a power transmission system is a standard bicycle, which has a sprocket and a chain to deliver power from the rider's legs to the wheels making the bike move.

Martin Sprocket & Gear manufactures power transmission and conveying products. The company was founded in 1951 and is headquartered in Arlington, TX. Martin provides tools that meet American National Standards Institute (ANSI), National Aerospace Standard (NAS), and Deutsches Institut für Normung (DIN) standards.