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ADD Addendum ANSI American National Standards Institute Addendum (ADD) Is the radial or perpendicular distance between the pitch circle and the top of the teeth. Alignment Accuracy of the alignment of shafts on which gears are mounted is a critical factor in their life and performance. Shafts should be set parallel in spur and helical gear sets, and perpendicular in most bevel and worm sets. Misalignment of shafts is one of the most common causes of premature gear failure or other performance issues such as noise. BHN Brinell Hardness Number, a measure of the hardness of a material such as steel, measured on the Brinell scale Backlash Is the amount by which the width of a tooth space exceeds the thickness of the engaging tooth on the pitch circles. Backlash Variation Is the difference between the maximum and minimum backlash occurring in a whole revolution of the larger of a pair of mating gears. Bevel Gears Are gears of conical form designed to operate on intersecting axes. These gears allow transmission of power "around corners" so to speak as their shafts intersect. Most commonly the shafts will intersect at a 90° angle. Straight bevel gears (as opposed to spiral bevel gears) have teeth that are straight, radially from the gears center point. Bore The diameter of the hole in a sprocket, gear, bushing, etc. Bottom Diameter The diameter of a circle measured across the bottoms of opposite tooth spaces. Sometimes referred to as the Root Diameter Bull Gear When considering a set of two gears one will usually be smaller than the other. The smaller gear is referred to as the pinion. The larger gear is sometimes call a "Bull" gear. Burning Cutting steel plate with a torch Bushing This term refers to a mechanical device used for mounting a sprocket or gear on a shaft. Several types of bushings exist including straight bronze sleeves and the split-tapered style, of which there are several (e.g. - B-Loc, Taper-Lock®, Q.D.®). CD Center distance CP Circular pitch Carburizing A heat treating process, which allows the surface of a low carbon steel gear or sprocket to be hardened to high hardness but to only a shallow depth. This process is usually applied "all over" or to the entire surface of the part. This type of treatment makes post heat-treat machining processes difficult. If desired, specific areas of parts can be masked prior to carburizing to prevent the introduction of carbon into the steel's surface and thereby preventing hardening of the masked areas when quenched. Center Distance (CD) Is the shortest distance between non-intersecting axes of mating gears. Circular Pitch (CP) Is the distance along the pitch line between corresponding profiles of adjacent teeth. Circular Thickness Is the thickness of the tooth on the pitch circle. Clearance Is the amount by which the dedendum in a given gear exceeds the addendum of its mating gear. In other words, it is the distance between the tip of one tooth and the bottom or root of its mate. Concentricity When two diameters share a common center they are said to be concentric. Deviations from theoretical or perfect concentricity are called eccentricity. Coupling Sprockets, Chains, and Covers A product line used for connecting two non-continuous shaft ends. D & T - drill and tap DED Dedendum DP Diametral pitch Dedendum (DED) Is the radial or perpendicular distance between the pitch circle and the bottom of the gullet. Diametral Pitch (DP) Is the ratio of the number of teeth to the number of inches in the pitch diameter. There is a fixed relation between diametral pitch (DP) and circular pitch (CP), namely CP = pi/DP. Double-Duty Extended Pitch Sprocket This describes Linn Gear Co. standard, stock Extended Pitch sprockets. With these sprockets one pitch of the chain spans across two teeth. When run on a sprocket with an odd number of teeth the chain rollers will alternate gullets on each revolution of the sprocket. The rollers will cycle through all of the sprocket's gullets every two revolutions of the sprocket. When an extended pitch chain is run on a sprocket with an even number of teeth the chain rollers will use only one set of the sprocket's gullets until the chain is manually reset to the second set. Two terms are used in describing the number of teeth on a double-duty extended pitch sprocket, Actual Number of Teeth and Effective Number of Teeth. The Actual Number of Teeth is exactly that. If you count the number of tooth projections on the perimeter of the sprocket you will get the Actual Number of Teeth. The Effective Number of Teeth is one half of the Actual and refers to the number of sprocket gullets utilized in one revolution of the sprocket. Single-duty Extended Pitch sprockets are available made-to-order. Double-Single Sprocket A double strand sprocket wide enough to operate with two single chains. These may be made up of two like sprockets or as a `Compound Double-Single' which is a combination of two sprockets of different pitch and/or number of teeth. Eccentricity When two diameters share a common center they are said to be concentric. Deviations from theoretical or perfect concentricity are called eccentricity. Extended Pitch (Large Roll) Sprockets designed to operate with large roll extended pitch series chain. Extended Pitch (Small Roll) Sprockets designed to operate with small roll extended pitch series chain.  |
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