Cam follower
Encyclopedia
A cam follower, also known as a track follower, is a specialized type of roller or needle bearing designed to follow cam
s. Cam followers come in a vast array of different configurations, however the most defining characteristic is how the cam follower mounts to its mating part; stud style cam followers use a stud
while the yoke style has a hole through the middle.
The first cam follower was invented and patented in 1937 by Thomas L. Robinson of the McGill Manufacturing Company. It replaced using just a standard bearing and bolt. The new cam followers were easier to use because the stud was already included and they could also handle higher loads.
End plates are used to contain the needles or bearing axially. On stud style followers one of the end plates is integrated into the inner race/stud; the other is pressed onto the stud up to a shoulder on the inner race. The inner race is induction hardened
so that the stud remains soft if modifications need to be made. On yoke style followers the end plates are peened
or pressed onto the inner race or liquid metal injected onto the inner race. The inner race is either induction hardened or through hardened.
Another difference is that a lubrication
hole is provided to relubricate the follower periodically. A hole is provided at both ends of the stud for lubrication. They also usually they have a black oxide
finish to help reduce corrosion.
element employed is a full complement of needle rollers. This design can withstand high radial loads but no thrust loads. A similar design is the caged needle roller design, which also uses needle rollers, but uses a cage
to keep them separated. This design allows for higher speeds but decreases the load capacity. The cage also increases internal space so it can hold more lubrication, which increases the time between relubrications. Depending on the exact design sometimes two rollers are put in each pocket of the cage.
For heavy-duty applications a roller design can be used. This employs two rows of larger rollers to increase the dynamic load capacity and provide some thrust capabilities. This design can support higher speeds than the full complement design.
For light-duty applications a bushing type follower can be used. Instead of using a type of a roller a plastic bushing is used to reduce friction, which provides a maintenance free follower. The disadvantage is that it can only support light loads, slow speeds, no thrust loads, and the temperature limit is 200 °F (93.3 °C). A bushing type stud follower can only support approximately 25% of the load of a roller type stud follower, while the heavy and yoke followers can handle 50%.
type applications to reduce skidding. Crowned followers can compensate for up to 0.5° of misalignment, while a cylindrical OD can only tolerate 0.06°. The only disadvantage is that they cannot bear as much load because of higher stresses.
stud. The stud has a bushing pushed onto it that has an eccentric outer diameter. This allows for adjustability during installation to eliminate any backlash
. The adjustable range for an eccentric bearing is twice that of the eccentricity.
Specialized track followers are also designed to withstand thrust loads so the anti-friction elements are usually bearing balls or of a tapered roller bearing
construction.
Cam
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...
s. Cam followers come in a vast array of different configurations, however the most defining characteristic is how the cam follower mounts to its mating part; stud style cam followers use a stud
Threaded rod
A threaded rod, also known as a stud, is a relatively long rod that is threaded on both ends; the thread may extend along the complete length of the rod. They are designed to be used in tension...
while the yoke style has a hole through the middle.
The first cam follower was invented and patented in 1937 by Thomas L. Robinson of the McGill Manufacturing Company. It replaced using just a standard bearing and bolt. The new cam followers were easier to use because the stud was already included and they could also handle higher loads.
Construction
While cam and followers appear to be very similar to roller bearings in construction they have quite a few differences. Standard ball and roller bearings are designed to be pressed into a rigid housing, which provides circumferential support. This keeps the outer race from deforming, so the race cross-section is relatively thin. In the case of cam followers the outer race is loaded at a single point, so the outer race needs a thicker cross-section to reduce deformation. However, in order to facilitate this the roller diameter must be decreased, which also decreases the dynamic bearing capacity.End plates are used to contain the needles or bearing axially. On stud style followers one of the end plates is integrated into the inner race/stud; the other is pressed onto the stud up to a shoulder on the inner race. The inner race is induction hardened
Induction hardening
Induction hardening is a form of heat treatment in which a metal part is heated by induction heating and then quenched. The quenched metal undergoes a martensitic transformation, increasing the hardness and brittleness of the part...
so that the stud remains soft if modifications need to be made. On yoke style followers the end plates are peened
Peening
Peening is the process of working a metal's surface to improve its material properties, usually by mechanical means such as hammer blows or by blasting with shot . Peening is normally a cold work process...
or pressed onto the inner race or liquid metal injected onto the inner race. The inner race is either induction hardened or through hardened.
Another difference is that a lubrication
Lubrication
Lubrication is the process, or technique employed to reduce wear of one or both surfaces in close proximity, and moving relative to each another, by interposing a substance called lubricant between the surfaces to carry or to help carry the load between the opposing surfaces. The interposed...
hole is provided to relubricate the follower periodically. A hole is provided at both ends of the stud for lubrication. They also usually they have a black oxide
Black oxide
Black oxide or blackening is a conversion coating for ferrous materials, copper and copper based alloys, zinc, powdered metals, and silver solder. It is used to add mild corrosion resistance and for appearance. To achieve maximum corrosion resistance the black oxide must be impregnated with oil or...
finish to help reduce corrosion.
Anti-friction element
The most common anti-frictionFriction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
element employed is a full complement of needle rollers. This design can withstand high radial loads but no thrust loads. A similar design is the caged needle roller design, which also uses needle rollers, but uses a cage
Cage (enclosure)
A cage is an enclosure made of mesh, bars or wires, used to confine, contain or protect something or someone. A cage can serve many purposes, including keeping an animal in captivity, capturing, and being used for display of an animal at a zoo.-History:...
to keep them separated. This design allows for higher speeds but decreases the load capacity. The cage also increases internal space so it can hold more lubrication, which increases the time between relubrications. Depending on the exact design sometimes two rollers are put in each pocket of the cage.
For heavy-duty applications a roller design can be used. This employs two rows of larger rollers to increase the dynamic load capacity and provide some thrust capabilities. This design can support higher speeds than the full complement design.
For light-duty applications a bushing type follower can be used. Instead of using a type of a roller a plastic bushing is used to reduce friction, which provides a maintenance free follower. The disadvantage is that it can only support light loads, slow speeds, no thrust loads, and the temperature limit is 200 °F (93.3 °C). A bushing type stud follower can only support approximately 25% of the load of a roller type stud follower, while the heavy and yoke followers can handle 50%.
Shape
The outer diameter (OD) of the cam follower (stud or yoke) can be the standard cylindrical shape or be crowned. Crowned cam followers are used to keep the load evenly distributed if it deflects or if there is any misalignment between the follower and the followed surface. They are also used in turntableTurntablism
Turntablism is the art of manipulating sounds and creating music using phonograph turntables and a DJ mixer.The word 'turntablist' was coined in 1995 by DJ Babu to describe the difference between a DJ who just plays records, and one who performs by touching and moving the records, stylus and mixer...
type applications to reduce skidding. Crowned followers can compensate for up to 0.5° of misalignment, while a cylindrical OD can only tolerate 0.06°. The only disadvantage is that they cannot bear as much load because of higher stresses.
Stud
Stud style cam followers usually have a standard sized stud, but a heavy stud is available for increased static load capacity.Drives
The standard driving system for a stud type cam follower is a slot, for use with a flat head screwdriver. However, hex sockets are available for higher torquing ability, which is especially useful for eccentric cam followers and those used in blind holes. The only problem with hex sockets is that it eliminates relubrication capabilities on that end of the cam follower.Eccentricity
Stud type cam followers are available with an eccentricEccentric (mechanism)
In mechanical engineering, an eccentric is a circular disk solidly fixed to a rotating axle with its centre offset from that of the axle ....
stud. The stud has a bushing pushed onto it that has an eccentric outer diameter. This allows for adjustability during installation to eliminate any backlash
Backlash (engineering)
In mechanical engineering, backlash, sometimes called lash or play, is clearance between mating components, sometimes described as the amount of lost motion due to clearance or slackness when movement is reversed and contact is re-established...
. The adjustable range for an eccentric bearing is twice that of the eccentricity.
Yoke
Yoke type cam followers are usually used in applications where minimal deflection is required, as they can be support on both sides. They can support the same static load as a heavy stud follower.Track followers
All cam followers can be track followers, but not all track followers are cam followers. Some track followers have specially shaped outer diameters (OD) to follow tracks. For example, track followers are available with a V-groove for following a V-track, or the OD can have a flange to follow the lip of the track.Specialized track followers are also designed to withstand thrust loads so the anti-friction elements are usually bearing balls or of a tapered roller bearing
Tapered roller bearing
Tapered roller bearings are bearings that can take large axial forces as well as being able to sustain large radial forces.-Description:...
construction.