 |
 |
  |
Glossary of Terms H A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y|Z HT - hardened teeth, indicates that the teeth of a sprocket or gear have been induction hardened HTD ® - is a Registered Trademark of the Gates Rubber Co. manufacturer of HTDr belts and sprockets; stands for High Torque Drive and refers to a particular style of toothed belt and sprockets compatible with those belts Helical Gears - Helical gear sets run on non-intersecting, parallel shafts. Instead of being parallel to the shaft axis (as with spur gears), the teeth of a helical gear spiral around the gears shaft axis. Placing the gear teeth on this kind of angle increases the amount of tooth surface in contact during operation. This allows for transmission of a higher load with a given size of gear set relative to spur gears. Use of the helix angle also creates end-thrust forces, which attempt to push the gears away from each other axially. These forces must be allowed for in any gear set design. Helix Angle - is the angle between a tangent to the helix and an element of the cylinder. Unless otherwise specified, the pitch helix is referred to. Herringbone Gears - Herringbone gear sets run on non-intersecting, parallel shafts. The tooth of a true herringbone gear is one continuous set of two opposing helices. The two helix angles come together in the center of the gear face to form a `V'. Gains in allowable load through increased tooth contact relative to spur gear sets of equal size are made. This is similar to helical gears, but with herringbone gears the end-thrust forces cancel themselves out. Cutting gears of this type is a difficult process which is made somewhat easier by machining a groove in the face at the point of the apex of the `V', creating a break in the middle of the herringbone gear tooth. This type of gear is technically a "Double- Helical" gear but is sometimes referred to as a herringbone if the center groove is narrow. Hob - a specialized cutting tool used for cutting teeth in sprockets and gears by the hobbing method Hub - a shoulder or flange protruding from the side of a sprocket or gear. Hubs provide width to a part, which is used, for mounting the part on a shaft. Hub Style - indicates the configuration of the hubs on a sprocket or gear. Type `A' indicates that the part has no hub; Type `B' indicates a hub on one side only and Type 'C' indicates a hub on both sides of the part. Type `A' sprockets are referred to as plate sprockets or "A plates". In the case of parts of fabricated construction the hub style indicates the projection of the hubs beyond the face width. Hypoid Gears - are gears similar in general form to bevel gears but designed to operate on non-intersecting axes. |