Precision
Since the assembly of ball and roller bearings involves very careful processing of the finest material, and delivery to the user in a finely adjusted condition , ball and roller bearings are used where precision of rotating elements must be of the highest order. The external dimensions of bearings are standardized as to nominal diameters and working tolerances, and in ball bearing and roller bearing plants of the present day the finest equipment is used, not only for processing but for the inspection of component parts, in order to insure the precision demanded by the principle of the bearing and the service into which it is to be placed.
Accurate and true-running bearings are for the first time possible with the ball and roller types, vibration, chatter,m and other undesirable conditions which may arise in plain bearings being largely eliminated by the proper selection and applications of anti-friction bearings to many types of machinery. Gears can be kept in exact alignment and adjustment. Grinding wheels can best supported as to produce the finest work, woodworking tools can be made to produce a more accurate finish, and at higher rates of speeds than would be possible with plain bearings. Parts which must be maintained with small but definite clearances are most successfully carried on ball bearings, and these qualities are only available during the initial period of operation but extend through their long and useful life.
Elsewhere are described the various degrees of precision which are available to the user of ball bearings. The so-called S.A.E. tolerances themselves are precision tolerances, but for even finer requirements still further degrees of accuracy are obtainable.
Lubrication
The load-carrying element in the plain or journal bearing is a firm of lubricant forced between the rotating and stationary surfaces by the action of the journal itself, and by the tendency of the lubricant to adhere to the stationary surface on the other side. This action drives a wedge of lubricant between the surfaces and separates them from actual metal – to – metal contact. The plain bearing is forced to rely upon this action for its effectiveness , while in the ball and roller bearing this condition does not apply, as rolling elements are interposed between the raceways. Lubricant, therefore, takes what may be termed a secondary (although important) place in the functioning of an anti-friction bearing. It lubricate the retainers, where they are in slight sliding contact with the balls, as well as the twilight zone where rolling friction verges on sliding friction, and it serves as a protector for the finely finished surfaces of the balls and raceways.
These considerations are responsible for the starting friction of ball and roller bearings being very low, and of plain bearings high. They press lubricating problems on teh designer and user of the plain journal to a far greater extent than with anti-friction bearings, where the rolling elements are kept in their proper relation with respect to the races by the retainer or separator, and maintain their location during service — in operation and out.
The design of housing for lubrication and the selection procedure in applying lubricant to the various ball bearing designs are treated separately in this catalog. In summing up, it is well to remember that anti-friction bearings will require comparatively little lubricant and offer a fairly wide choice of grease or oils. Maintenance is low and periods between lubrication can be unusually long.
Since the assembly of ball and roller bearings involves very careful processing of the finest material, and delivery to the user in a finely adjusted condition , ball and roller bearings are used where precision of rotating elements must be of the highest order. The external dimensions of bearings are standardized as to nominal diameters and working tolerances, and in ball bearing and roller bearing plants of the present day the finest equipment is used, not only for processing but for the inspection of component parts, in order to insure the precision demanded by the principle of the bearing and the service into which it is to be placed.
Accurate and true-running bearings are for the first time possible with the ball and roller types, vibration, chatter,m and other undesirable conditions which may arise in plain bearings being largely eliminated by the proper selection and applications of anti-friction bearings to many types of machinery. Gears can be kept in exact alignment and adjustment. Grinding wheels can best supported as to produce the finest work, woodworking tools can be made to produce a more accurate finish, and at higher rates of speeds than would be possible with plain bearings. Parts which must be maintained with small but definite clearances are most successfully carried on ball bearings, and these qualities are only available during the initial period of operation but extend through their long and useful life.
Elsewhere are described the various degrees of precision which are available to the user of ball bearings. The so-called S.A.E. tolerances themselves are precision tolerances, but for even finer requirements still further degrees of accuracy are obtainable.
Lubrication
The load-carrying element in the plain or journal bearing is a firm of lubricant forced between the rotating and stationary surfaces by the action of the journal itself, and by the tendency of the lubricant to adhere to the stationary surface on the other side. This action drives a wedge of lubricant between the surfaces and separates them from actual metal – to – metal contact. The plain bearing is forced to rely upon this action for its effectiveness , while in the ball and roller bearing this condition does not apply, as rolling elements are interposed between the raceways. Lubricant, therefore, takes what may be termed a secondary (although important) place in the functioning of an anti-friction bearing. It lubricate the retainers, where they are in slight sliding contact with the balls, as well as the twilight zone where rolling friction verges on sliding friction, and it serves as a protector for the finely finished surfaces of the balls and raceways.
These considerations are responsible for the starting friction of ball and roller bearings being very low, and of plain bearings high. They press lubricating problems on teh designer and user of the plain journal to a far greater extent than with anti-friction bearings, where the rolling elements are kept in their proper relation with respect to the races by the retainer or separator, and maintain their location during service — in operation and out.
The design of housing for lubrication and the selection procedure in applying lubricant to the various ball bearing designs are treated separately in this catalog. In summing up, it is well to remember that anti-friction bearings will require comparatively little lubricant and offer a fairly wide choice of grease or oils. Maintenance is low and periods between lubrication can be unusually long.
No comments:
Post a Comment