FIG. 4–32. Parts of a plain roller bearing.
FIG. 4–33. The various parts of two applications of a spiral roller bearing. (Hyatt Roller Bearing Co.)
Straight roller bearings can be further divided into (1) the plain roller (Fig. 4–32), (2) the spiral roller (Fig. 4–33), and (3) the needle bearing (Fig. 4–34). The plain, straight roller bearing consists of a number of solid-cylinder steel rollers assembled in a cage with an inner and outer race (Fig. 4–35). One further classification of plain roller bearings is determined by the manner in which the parts are assembled, as a bearing with a separable inner race, a bearing with a separable outer race, and a bearing with nonseparable parts.
FIG. 4–34. The various parts of a needle roller bearing. (Torrington Roller Bearing Company.)
The spiral, or wound, straight, hollow roller bearing is shown in Fig. 4–33. Types are designed to operate with inner and outer races or with no inner race and a split outer race.
The needle-type roller bearing consists of a hardened outer shell containing a number of hardened rollers with pointed ends (Fig. 4–34). The needle bearing has the greatest radial load capacity possible for a given housing bore. It can also be used where the bearing space is limited.
FIG. 4–35. The various parts of a tapered roller bearing. (Timken Roller Bearing Company.)
FIG. 4–36. Application of tapered roller bearings on a disk harrow. (Timken Roller Bearing Company.)
Tapered roller bearings are designed to carry radial, or thrust loads, or a combination of both. The conical rollers are set in the cage at an angle between the inner and outer races as shown in Fig. 4–35. It is usually necessary to mount tapered roller bearings in pairs, to balance the radial and thrust loads (Fig. 4–36). Their greatest application is for wheel bearings, but there are many other applications.
Maintenance of Antifriction Bearings. Good maintenance of antifriction bearings is essential to obtain a long, trouble-free life service. All persons who operate and repair farm equipment should obtain a bearing-maintenance handbook from a bearing manufacturer. These handbooks describe and illustrate replacement of bearings, their care, cleaning, and selection, and the use of lubricants.
FIG. 4–37. Two types of bearing bushings: top, straight bushings showing types of grooves for oil; bottom, types of grooves for graphited oilless bearing.
Bushings. A bushing is a replaceable lining for a bearing. It may consist of wood, babbitt, bronze, chilled iron, or other material. Figure 4–37 shows two types of bearing bushings with different types of grooves for distributing the oil along the shaft.
Keys. Keys are of two kinds: first, those that fit into a slot in both the shaft and pulley, holding the two firmly together and causing them to turn as a unit; second, the cotter or split keys that are put through a hole in the end of a bolt or pin to hold the nut and washer on.
Bolts. The great variety of bolts used in the construction of farm machinery may be classified as follows: machine, carriage, stove, and plow bolts.
FIG. 4–38. Types of bolts: A, machine; B, carriage; C, plow; D–G, stove.
FIG. 4–39. Types of special bolts.
Machine bolts are used for holding two pieces of metal together. They have a square or hexagonal head with the stem of the bolt fitting into the head without any change of diameter, as Fig. 4–38.
Carriage bolts (Fig. 4–38), unlike machine bolts, have a rounded or oval-surfaced head with a square shoulder underneath extending out some half an inch, varying according to the size of the bolt.
Plow bolts may have many different kinds of heads, but practically all of them have from one to four shoulder-like points that fit into a groove prepared for them in whatever material they are placed. The undersides of the heads of plow bolts are always countersunk (Fig. 4–38), so that the head may go deep enough into the material to fit flush with the surface. Such bolts are used for holding plowshares.
Stove bolts, as shown in Fig. 4–38, are rather short bolts having threads running down close to the head, which may be either flat or round. Most stove bolts also have a slot cut across the heads, so that screw drivers may be used to prevent them from turning. This type of bolt is used for bolting thin metal together. Some special bolts are shown in Fig. 4–39.
Nuts. The most common types of nuts used on farm machinery are shown in Fig. 4–40. The square nut is used on the cheaper machines, but the hexagon nut is used on the higher-class machines. Castellated nuts are used where vibration is likely to cause the nut to work loose. Wing nuts are used where it is necessary to remove a part frequently. Lock nuts are constructed so that they automatically lock themselves in place.
FIG. 4–40. Types of nuts: A, square; B, hexagon; C, castellated; D, wing; E, square lock.
Screws. Many types of screws are also used in the construction of farm machinery. They may be classified as follows: set, cap, lag, and wood.
Setscrews (Figs. 4–41 to 4-43) may have several