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OD Outside diameter Operating Pitch Diameters Are the pitch diameters determined from the numbers of teeth and the center distance at which gears operate. Outside Diameter (OD) The diameter of the circle which contains the tops of the teeth of an external gear or sprocket. PA Pressure angle PD Pitch diameter Pinion When considering two sprockets or gears that run together the one with the smaller number of teeth is called the pinion. Pitch In general terms, pitch is a measure of the size of the teeth of a sprocket or gear. It is the distance between two teeth at the pitch diameter. The larger the pitch, the larger the teeth. Several systems are used to designate pitch in gears, such as Diametral Pitch, Circular Pitch and Module. In describing sprockets a number (e.g. - 35, 120, 2040) designates the pitch, as well other defining dimensions of the sprocket and chain. Pitch Angle Is the angle between an element of a pitch cone and its axis. Pitch Diameter (PD) Is the diameter of the pitch circle. In parallel shaft gears, the pitch diameters can be determined directly from the center distance and the number of teeth by proportionality. Operating pitch diameter is the pitch diameter at which the gears operate. Pitch Diameter of a Sprocket The circle traced by the path of the chain pin centers as the chain travels around the sprocket. Plain Bore This term is used to indicate that the center hole in a sprocket or gear has no keyway, set screw(s), bushing or any other type of machined preparation for shaft mounting. Plain bores may be machined to a specified tolerance or a nominal tolerance. Plain bores are also referred to as mandrel bores or stock bores. Pressure Angle (PA) Is the angle between a tooth profile and the radial line at its pitch point. In involute teeth, pressure angle is often described also as the angle between the line of action and the line tangent to the pitch circle. Standard pressure angles are established in connection with standard gear-tooth proportions. Q.D.® Is a Registered Trademark of Emerson Electric Co., stands for Quick Detachable and refers to a split-tapered bushing system. RC Hardness of steel measured on the Rockwell `C' scale Rack Linn Gear Co. manufactures spur gear rack, which is a straight length of square or rectangular steel bar with teeth on one side, across which a pinion is driven. Technically a gear rack is a spur gear with an infinite pitch diameter. Rack Tooth Sprockets A sprocket tooth form designed to run a length of chain on a straight line, similar to gear rack. Ready Sprocket An exclusive line of single strand sprockets and a series of interchangeable bolt-on hubs. This system allows easy assembly of single and double-single sprockets in a wide variety of pitches, numbers of teeth and bore sizes. The detachable hubs cut sprocket replacement costs by as much as 50% and making stocking very economical. Roll Diameter or "Roll" Is the diameter of the roller in Roller Chain. The roller is the element of the chain which actually makes contact with sprocket teeth. It is also referred to as the barrel. Roll diameter is one of the primary defining characteristics of a sprocket. Roller Chain Is the most commonly used type of chain used in industry. Many variations exist but in simple terms a roller chain consists of sidebars or plates, rollers, bushings and pins which can be assembled into a continuous loop of a specific desired length and used to transmit power among mechanical components. Root Diameter (RD) The diameter of the bottoms of the tooth gullets of a sprocket or gear (also referred to as the bottom diameter) SB Stock bore SS This abbreviation is used for both Stainless Steel and Set Screw, caution should be exercised in its use and interpretation. Set Screw Asocket head screw, which is screwed tight against a key or shaft in order to fix a sprocket or gear on that shaft with pressure and friction. Speed Reduction When transferring energy from a high-speed source such as a motor to a lower speed application, some method of reducing shaft speeds is required. Sprocket and gear systems are typical mechanical methods for achieving required speed reduction through a desired combination of tooth ratios. For example: If a 20 tooth pinion is driven by a 3600 RPM motor, and the pinion in turn drives a 120 tooth gear, the ratio of reduction would be 6:1 or 1/6 of the input speed; equaling 600 RPM at the gear. If the specific application requires a lower operating than that provided by the first stage of reduction a second stage may be applied by placing additional gears in series until the desired output speed is achieved. Spiral Bevel Gears In similar fashion to helical gears, higher potential load transmission relative to straight bevel gears is achieved with spiral bevel gears by cutting the teeth in a curved shape. Split Sprockets and gears can be manufactured by several methods, which allow them to be split in half. Splitting allows for installation of the parts without disassembling the machinery they are going into. Spur Gears Are gears cylindrical in form, with teeth that are straight and parallel, and operate on parallel axes. Strand This is a term used to describe sprockets. A Strand is one 360° circular array of equally spaced sprocket teeth allowing continuous operation of one width of chain. Roller chains are manufactured in single or multiple widths. Multiple width chains require multiple-strand sprockets, where the strands are properly spaced to fit within the interconnected sidebars of the chain. Multiple strand chains allow transmission of higher loads for a given pitch of chain. Chains are commonly available for single, double, triple and quadruple (or simply `quad') strand sprockets. TL - Taper-Lock® Taper-Lock® Is a Registered Trademark of Dodge/Rockwell Automation and refers to a split-tapered bushing system Weld-In Adapter A steel hub drilled, tapped and bored to fit a specific bushing such as a Taper-Lock®, Q.D.®; (also referred to as weld-in hubs) Worm & Worm Gear Worm gear sets run on non-intersecting, perpendicular shaft axes and provide high ratios of reduction. The worm is a threaded cylindrical shaft, which drives the worm gear (also referred to as the worm wheel). Worm gears look somewhat similar to helical gears except that they have a curved throat recessed in their face to allow the worm access to the flanks of the gear teeth. Worm gears are almost always made from bronze or cast iron with the worms made from steel. This combination of materials allows for the sliding action between the gears. Worms may have a single start (continuous thread) or multiple starts.  |
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