Machinery's Handbook, 31st Edition
2440 Plain Bearing Materials Porous Metals.— Porous metal self-lubricating bearings are usually made by sintering metals such as plain or leaded bronze, iron, and stainless steel. The sintering produces a spongelike structure capable of absorbing fairly large quantities of oil, usually 10–35 percent of the total volume. These bearings are used where lubrication supply is difficult, inadequate, or infrequent. This type of bearing should be flooded from time to time to resaturate the material. Another use of these porous materials is to meter a small quantity of oil to the bearings such as in drip feed systems. The general design operating character istics of this class of materials are shown in Table 4. Table 4. Application Limits — Sintered Metal and Nonmetallic Bearings
Maximum Temperature Surface
PV Limit P = psi load V = surface ft/min
Load Capacity
Speed, V max (max. fpm)
Bearing Material
psi
kPa 6895 4137 4137 6895
° F
° C
Acetal
1000 600 600 1000 6000 4500 8000
180 82 1000 750 399 2500 750 399 2500 200 93 1000 200 93 2500 160 71 1500
3000 15,000 150,000
Graphite (dry)
Graphite (lubricated) Nylon, Polycarbonate Nylon composite
3000
… … 400 204
… 16,000
Phenolics
41369 31026 55158
15,000 50,000 50,000 50,000
Porous bronze Porous iron Porous metals
160 71
800
4000–8000 27579–55158 150 66 1500
500 2500
3447 17237
500 260
50
1000
Virgin Teflon (TFE) Reinforced Teflon
500 260 1000
10,000–15,000
TFE fabric
60,000
413685 500 260
150
25,000 15,000 15,000
Rubber
50
345
150 66 4000 150 66 2000
Maple & Lignum Vitae 2000
13790
1 fpm = 0.3048 m/min; 1 psi = 6.8947 kPa Table 5a, Table 5b, and Table 5c give the chemical compositions, permissible loads, interference fits, and running clearances of bronze-base and iron-base metal-powder sin - tered bearings that are specified in the ASTM specifications for oil-impregnated metal- powder sintered bearings (ASTM B438-17 and B439-19). Plastics Bearings.— Plastics are finding increased use as bearing materials because of their resistance to corrosion, quiet operation, ability to be molded into many configura tions, and their excellent compatibility, which minimizes or eliminates the need for lubri cation. Many plastics are capable of operating as bearings, especially phenolic, tetrafluo - roethylene (TFE), and polyamide (nylon) resins. The general application limits for these materials are shown in Table 4. Laminated Phenolics: These composite materials consist of cotton fabric, asbestos, or other fillers bonded with phenolic resin. They have excellent compatibility with various fluids as well as strength and shock resistance. However, precautions must be taken to maintain adequate bearing cooling because the thermal conductivity of these materials is low. Nylon: This material has the widest use for small, lightly loaded applications. It has low frictional properties and requires no lubrication. Teflon: This material, with its exceptional low coefficient of friction, self-lubricating characteristics, resistance to attack by almost any chemicals, and its wide temperature range, is one of the most interesting of the plastics for bearing use. High cost combined
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