Introduce shaft collar

Shaft collars are one of the simplest components in machine design but are also one of the most indispensable.
Shaft collars can be found in virtually any type of machinery and are frequently accessories to other components. Capable of fulfilling many roles, shaft collars often hold bearings and sprockets on shafts, situate components in motor and gearbox assemblies, and serve as mechanical stops.
There are a variety of factors that determine which collar is ideal for an application. It is important to carefully identify all the relevant requirements, parameters, and limitations of your system before selecting a shaft collar.
"While it is important to understand how effective a shaft collar will be in an application, many assemblies benefit from or require a specific style. Some shaft collars will require infrequent adjustment or disassembly after the initial installation. In this case, a one-piece clamp type or set screw shaft collar may be suitable as either can be installed quickly and easily. In other assemblies, the collar needs to be disassembled frequently and there are other difficult-to-remove components installed on the shaft. In this case, a two-piece style is beneficial as it can be installed and removed without disturbing other components.
Quick clamping shaft collars with a cam lever or clamping lever are ideal for applications that require frequent axial adjustment along the shaft. By skipping the manual torqueing of the screw, adjustments with this style of collar are several times faster and more convenient.
Other applications, such as packaging, printing, medical, and food may have space or weight restrictions but low holding power requirements. In this situation, a thin line shaft collar may be suitable due to their reduced width, weight, and screw size. Conversely, large shafting may require high axial loads that a standard style can not accommodate and a heavy duty shaft collar would be preferred ."
In many applications, holding power is the key performance factor designers are looking for. It is affected by a variety of collar specifications and affects the collar's maximum axial load. A set screw collars holding power is dependent on how much the screw can impinge into the shaft, which is a function of the relationship between the screw and shaft materials.
"All things being equal, the holding power of each style of shaft collar increases from left to right: quick
clamping, set screw, thin line, standard clamp types, double wide, heavy duty, threaded/bearing locknut.
Bore size and concentricity influence the holding power of Clamp style shaft collars , however the importance of fastening hardware cannot be understated. The size and quality of hardware, namely thread quality, tensile strength, and size tolerances, affect how much torque the screw can transmit to the collar. Forged screws are generally superior to broached screws as they are more consistent and are less likely to ream out. Likewise, the collar itself must be manufactured from a material strong enough to withstand the recommended screw torque or else it may crack or deform.
Small bore one-piece clamp style shaft collars (1-5/8” or 38mm and under) are often machined with a back-cut opposite to the clamp cut. The back-cut reduces the cross-sectional area at the hinge point of the collar lowering the force required of the screw to clamp the collar around the shaft. This allows the screw to use more of its seating torque for holding power. As one piece-collars move up in size the size and strength of the screw increases to a point where the back-cut is no longer needed. Two-piece styles reduce the amount of material that must be bent around the shaft and have the added advantage of a second screw to transmit torque. Even with these benefits holding power is only increased by about 5%. The choice between a one-piece or two-piece design largely comes down to convenience and the disassembly requirements of an application.
he surface treatment on a shaft collar and its screw(s) is another factor that contributes to holding power.
"Shaft collars and their screws are most frequently steel with either a black oxide or zinc plated surface finish. The most common shaft collars are steel with black oxide finish, which enhances the torque of the screws yet does not significantly diminish the frictional characteristics of the bore with a net increase in holding power.

Black oxide enhances holding ability and helps keep the torque rating of the screw within its design parameters. Zinc plating is more corrosion resistant but reduces the collar's friction coefficient, reducing its holding power ."
Black oxide is effective largely because it is an anti-stick slip compound.
Stick-slip is the false impression that a screw has been tightened to the appropriate stress level. Instead of the screw rotating uniformly as the torqueing continues, there is a point at which the uniform rotation converts to a stop and start pattern. The tensioning effort on the screw is being absorbed as excess friction between the threads or the underside of the head and the mating parts of the clamp body, instead of contributing to the stress in the joint elements. If the stresses are low, the collar will not hold well.
As well as their holding power, a primary performance characteristic of shaft collars is their ability to locate and align other shaft components with a precisely machined bearing face. In order to assure this level of precision, high performance shaft collars are single point faced at the same time that the bore is finished. This results in very low run-out when the collar is mounted on the shaft, which is extremely important when interfacing with other precision components.
Clamp-style shaft collars in both one- and two-piece styles allow for easy installation and adjustment and are used commonly to locate components on a shaft, such as sprockets, gears, pulleys, and ball bearing units. In these cases the ability to retain axial loads is important, but the perpendicularity of the collar face to the shaft is critical.
A precise face-to-bore relationship ensures squareness of the component to the shaft with no shifting or tilting relative to the shaft axis. Such displacements can cause premature wear and possibly affect the performance of the assembly. In cases sprockets or pulleys are used with chain or belts, the alignment of the component is critical to proper operation. Failure to maintain alignment can result in unacceptable performance, including excessive noise, slippage, whipping, rapid wear or total failure, depending on the application.
Precision facing ensures squareness of the collar face with the bore allowing for even pressure at the interface between the collar and mounted component,eliminating spot loading which can shorten life of the components. In applications collars are used against bearings, this is an extremely important characteristic since uneven loading of bearings is detrimental to long life and high performance.
p>This is also beneficial in applications that see moderate axial shock loading such as linear actuators. In applications such as these, the collar is used as a mechanical stop, face squareness is important to assure even force distribution across the face of the collar to minimize the impact pressure and ensure that the collar does not shift position on the shaft.
Material can have a significant impact on the performance of a shaft collar in a given system.
Aluminum shaft collars are lightweight and have good holding power, making them a common choice in many applications. Steel shaft collars possess the highest holding power and some corrosion resistance but are heavier than aluminum collars. The steel grade can have an impact on collar performance depending on the application. While 12L14 is easier to machine than 1215, it is not well suited for applications where the collar will be welded to another component due to the lead content. Stainless steel collars have increased corrosion resistance over aluminum and steel types, however they have reduced holding power when compared to shaft collars that use steel hardware. Stainless steel collars are most commonly found in 303, 304, and 316 stainless steel. It is critical that designers consider the material of the shaft collar and screw prior to selection. For example, manufacturers may offer a 316 stainless collar with an 18-8 stainless screw. While the shaft collar will be able to withstand the harsh environment, the screw will not, leading to reduced performance and premature failure.
Although most shaft collars are manufactured from aluminum or varieties of steel, some collars are made of less common materials. Plastic shaft collars are lightweight and inexpensive when used as an alternative to stainless steel types, however they have greatly reduced holding power. Titanium collars are lighter than aluminum, have good holding power, do not outgas (useful for cleanroom environments), and can tolerate extreme temperatures. However, they are only used if the application absolutely requires these properties due to their prohibitively high cost.
Screw treatment is equally important for stainless steel collars.
If screws are untreated prior to installation galling will occur as the material of the collar and screw are the same. This can make the collar harder to disassemble and may only allow for a single use. If disassembly is required, the screw may be bound to the collar in such a way that it can be taken out complicating removal.
Since the strength of the screw itself has a dramatic effect on the collar's holding power, the strength of the screw material in relation to that of the collar is important. Generally, the manufacturer will offer the appropriate screw for the collar, however it may be sensible in some applications to use a non-standard screw understanding it will adversely impact collar performance.
Despite being somewhat simple components, shaft collars can be complicated and critical to the performance of an application. Designers have many factors such as style, material, bore size, and shaft geometry to consider before a selection can be made.
We hope we can help users make a more informed decision. If additional help is needed, you can always contact us.thanks