Shaft collars are a simple solutions for locating components, mechanical stops and bearing faces on a shaft. Only a few parts make this simple machine component. Robust and easy to install this component has found its use in many places. Over the years few different types where invented each one with a different best use case. Shaft collar are supposed to connect to a shaft with a non-permanent connection in other words so that they can move and their position be adjusted on a shaft.
Shaft collar types
Set screw shaft collars
There are several shaft collar types that are in use today. The first shaft collars where set screw type. As the one shown in the picture bellow. This type of collar uses a set screw to lock onto a shaft. By tightening it, a set screw digs into the shaft and deforms it a bit so that the collar does not slip. This connection works only when the material of the shaft is softer then the material of the screw. So for hardened shafts this is not a good option. Also this shaft collar should not be used with precision rods because of this material deformation that the connection creates. Another drawback of this material deformation is that in order to adjust the collar slightly you need to rotate a collar and make another deformation point on the shaft.
Besides these drawbacks it is a cheep and effective solution in many cases. This part is also standardized in many organizations in DIN it is DIN 705 and DIN 703 – a slight variation with two set screws.
One piece Clamp Style Shaft Collars
One piece Clamp style shaft collars are a great improvement over the set screw style. The connection between the shaft and the collar is made with friction. There is no screw tightening on a shaft so there is no shaft deformation. Tightening the screw on a clamp connects the collar to the shaft. Flexing of the collar takes up one part of the force from tightening a screw and a larger part is used to bind the collar onto a shaft. These collars have a higher holding power then the set screw type and are very easy to install.
Two piece Clamp Style Shaft Collars
Two piece collars are made out of two halves that are connected with bolts. The connection to the shaft is also with friction. These collars have a higher holding power than the one piece type. There are two reasons for this. One, the two piece collar has double the amount of screws the one piece has. This results in higher clamping force and greater friction between the collar and the shaft. Two, the part of the force is not used up to flex the clamp like in the one piece type. Two piece clamp shaft collars have another advantage over other types and that is that they do not have to be slit onto a shaft. You can separate the two pieces and then connected them on the desirable place. Sometimes when you have gears, sprockets and bearing mounted on a shaft this makes for a lot easier assembly. Sometimes these are the only types of shaft collars that can be assembled because of this. These collars frequently have one side ground perfectly perpendicular to the bore. This is face is used to seat up to a bearing.
Quick- Clamping collars are a variation of a one piece collar style. The principal of the connection is the same. The only difference is that instead of tightening a screw you can just use the lever to open and close the collar. This is a lot faster and does not require any tools. This is why it is used in application where adjustments of the collar are frequent, usually done by the machine operator.
Threaded shaft collars are a type of shaft collars that have a thread on its inside diameter. These collars are made in one piece and two piece variations. These collars are used to limit mechanical movement of the components that are driven with a screw. The connection made between a threaded rod and shaft collar is not just a friction connection. There is an interference between the threads on the collar and the threads on the threaded rod. This makes for a very strong connection. The chances are that the threaded rod willbreak before the collar connection.
Uses for Shaft Collars
As mentioned, shaft collars are used for locating components, mechanical stops and bearing faces on a shaft. Here are some examples that might inspire your next project.
Sprockets, gears and other machine components on the shaft can be located with a shaft collar.
This example shows how set type shaft collar is used to locate idler for a belt drive. This solution is better than using snap rings because you can adjust the location of the idler as needed.
Holding and positioning sensors are also a great use for shaft collars. When machine is assembled and tested there is often a need to adjust the location of the sensors. Therefore using shaft collars is a good solution.
I hope that this post gives you some starting insight in how to implement shaft collars in your next design.
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