Ball bearings with precision levels less than ABEC 1 are considered to be unground bearings. Applications include ceiling fans, hoists, and trailer jacks – just to name a few. Semi-ground bearings are also available, but precision bearings meet at least ABEC level 3 . Precision bearings are more challenging to produce, but they support high accuracy, high rigidity, and high speeds.

Groof meaning

Deep groove ball bearings can support heavy loads while offering both axial and radial support. The term “groove” refers to the depth of the raceway into which the balls fit.

When the contacting end of the follower has a sharp knife edge, it is called a knife edge follower, as shown in Fig. 2(a). The sliding motion takes place between the contacting surfaces (i.e. the knife edge and the cam surface). It is seldom used in practice because the small area of contacting surface results in excessive wear. In knife edge followers, a considerable side thrust exists between the follower and the guide.

In addition to materials of construction, ball bearings are specified by dimensions, rated speed, dynamic axial load, and dynamic radial load. Bore diameter, outside diameter, cross section and overall width are key dimensional specifications. With standard ball bearings, the cross section increases in proportion to the bore diameter. With thin section bearings, however, the cross-section dimension does not. In other words, the cross-section size remains the same even when the bore diameter increases.

When the contacting end of the follower is a perfectly flat face, it is called a flat-faced follower, as shown in Fig. 2 (c). It may be noted that the side thrust between the follower and the guide is much reduced in case of flat faced followers. The only side thrust is due to friction between the contact surfaces of the follower and the cam. The relative motion between these surfaces is largely of sliding nature but wear may be reduced by off-setting the axis of the follower, as shown in Fig. 2 (f ) so that when the cam rotates, the follower also rotates about its own axis. The flat faced followers are generally used where space is limited such as in cams which operate the valves of automobile engines.

Fig. 3 shows a radial cam with reciprocating roller follower. The following terms are important in order to draw the cam profile

Ball bearings have two ring-shaped races, or raceways, that hold the individual balls and transmit loads through them. These races provide a fixed path on which balls can roll and glide while generating little friction. Each race has a grooved surface, and some are grooved more deeply than others. The outer race contacts the outside of the balls, the inner race contacts the inside of the balls, and the balls remain between these two races.

Rollingbearing

It is the smallest circle that can be drawn from the centre of the cam and tangent to the pitch curve. For a knife edge and a flat face follower, the prime circle and the base circle are identical. For a roller follower, the prime circle is larger than the base circle by the radius of the roller.

It is the curve generated by the trace point as the follower moves relative to the cam. For a knife edge follower, the pitch curve and the cam profile are same whereas for a roller follower, they are separated by the radius of the roller.

Needle rollerbearing

Angular contact ball bearings have inner and outer raceways that are displaced relative to each other in the direction of the bearing axis. This enables them to accommodate combined radial and axial loads.

A ball bearing is a mechanical assembly that carries loads, reduces friction, supports positioning, and facilitates rotational and/or oscillatory motion. It is more than just than just a single BB-shaped ball.  Ball bearings can be manufactured with a higher or lower level of precision and are used in a variety of applications. Precision bearings are required by the aerospace, military and defense, medical, and semiconductor industries.

When the contacting end of the follower is of spherical shape, it is called a spherical faced follower, as shown in Fig. 2 (d). It may be noted that when a flat-faced follower is used in automobile engines, high surface stresses are produced. In order to minimise these stresses, the flat end of the follower is machined to a spherical shape.

Ball bearing

When the motion of the follower is along an axis passing through the centre of the cam, it is known as radial follower. The followers, as shown in Fig. 2 (a) to (e), are all radial followers

There are many different types of ball bearings, including various subtypes. The following is a partial list with some brief definitions and use cases.

Cams are mechanical devices which are used to generate curvilinear or irregular motion of mechanical elements. They are used to convert rotary motion into oscillatory motion or oscillatory motion into rotary motion.Necessary elements of a cam mechanism are:

Thrustbearing

Bearing

It is a reference point on the follower and is used to generate the pitch curve. In case of knife edge follower, the knife edge represents the trace point and the pitch curve corresponds to the cam profile. In a roller follower, the centre of the roller represents the trace point.

A ball bearing retainer (also called a cage) is a separator that maintains the balls’ radial spacing from each other. Retainers can also provide lubrication by serving as a reservoir for oils or supplying a solid film. There are several common types of cages, including special cages for aircraft bearings. Prior to assembly, the retainers are cleaned carefully and then lubricated. With some precision bearings, military-grade greases are required.

When the contacting end of the follower is a roller, it is called a roller follower, as shown in Fig. 2 (b). Since the rolling motion takes place between the contacting surfaces (i.e. the roller and the cam), therefore the rate of wear is greatly reduced. In roller followers also the side thrust exists between the follower and the guide. The roller followers are extensively used where more space is available such as in stationary gas and oil engines and aircraft engines.

Rolling elementbearing

It is the angle between the direction of the follower motion and a normal to the pitch curve. This angle is very important in designing a cam profile. If the pressure angle is too large, a reciprocating follower will jam in its bearings.

Balls can be made of stainless steel, glass, acetal, ceramic, or polypropylene. In addition, the balls and races can be made of the same material or different materials. Typically, precision bearings for aerospace, aircraft and aviation use SAE 52100, 440C or 440C modified steel, CREN high nitrogen stainless steel, or M50. Hybrid bearings with ceramic elements for higher speeds and extended wear life are also used in demanding applications.

Schatz Bearing is ball bearing supplier that designs and manufactures products in an ISO 9001:2015 and AS9100 Rev. D certified facility in Poughkeepsie, New York (USA). We are also ITAR registered and can supply you with bearings that meet Boeing standards or MIL-SPEC standards.

Precision ball bearings include both angular contact bearings and deep groove bearings. Therefore, the definition of a precision bearing involves manufacturing. A ball bearing’s ABEC rating describes the level of manufacturing tolerances, or acceptable part-to-part variations. Bearings with lower ABEC ratings are less precise and bearings with higher ABEC ratings are more precise.

When the motion of the follower is along an axis away from the axis of the cam centre, it is called off-set follower. The follower, as shown in Fig. 2 ( f ), is an off-set follower.

ballbearing中文

Full complement bearings don’t have a cage. Instead, both rings have filling slots to allow the maximum number of balls to be installed in the bearings. This results in a much higher load-carrying capacity, but there are tradeoffs. For example, full complement bearings are used only in applications that have radial loads. In other words, they can’t support thrust or moment loads. Typically, full complement bearings are used in slower speed applications.

A cam is a rotating machine element which gives reciprocating or oscillating motion to another element known as follower. The cam and the follower have a line contact and constitute a higher pair. The cams are usually rotated at uniform speed by a shaft, but the follower motion is predetermined and will be according to the shape of the cam. The cam and follower is one of the simplest as well as one of the most important mechanisms found in modern machinery today. The cams are widely used for operating the inlet and exhaust valves of internal combustion engines, automatic attachment of machineries, paper cutting machines, spinning and weaving textile machineries, feed mechanism of automatic lathes etc.