What is the function of a shaft collar?
Shaft collars have extremely diverse applications.
Shaft collars have been used on applications from holding up a flag on a flag pole,
to positioning devices on medical equipment to the more common industrial applications
of holding other shaft components such as bearings, sprockets and pulleys in place.
In general, shaft collar applications fall into one of three broad categories:
- Postioners: Locate or position a component on a shaft
- Spacers: Keep components "spaced" apart
- Limiters: Limit the movement of a shaft such as in a reciprocating application
What is the history of the shaft collar?
Set-screw collars were the first type of shaft collar used. These collars were mass-produced
and used on line-shafting in mills. In the 1900's, in response to safety concerns of the
protruding head, the safety set collar with a recessed head socket set screw was introduced.
Around the time of World War II, the clamp type collar was introduced. The
clamping collar gripped the shaft without marring the shaft as the set-screw collar did. The clamping collar also
had a greater holding power.
Since then other styles such as two-piece clamping collars and threaded collars have been introduced.
What are the different types of shaft collars?
Set Screw Collar
The set-screw collar is the most common and most economical shaft collar. As the name indicates, the collar holds onto the shaft via a set screw that presses into the shaft. This penetration of the point screw into the shaft provides most of the holding power though friction between the shaft and the collar also contributes slightly.
The economy of set-screw collars is offset by some disadvantages. One, the set-screw mars the shaft. Two, the set-screw collar provides less holding power than a clamping collar. Three, it is much less effective on a shaft that is harder than the set screw because the screw can make little or no penetration into shaft.
Set-screws are available with knurled points, which make a deeper penetration into the shaft and offer greater holding power. Additionally, a second set screw, usually spaced 90 to 120 degrees apart from the first screw, can greatly increase the holding power.
One-Piece Clamping Collars
The one-piece clamping collar has a tangential screw, which when tightened grips the shaft collar onto the shaft without marring the shaft and provides greater holding power than a set-screw collar.
Two-Piece Clamping Collar
The two-piece clamping collar has two tangential screws. The main advantage of the two-piece
collar is that it can be installed without having to remove other components on the shaft.
The two-piece collar also provides more holding power than the one-piece clamping collar.
With a one-piece collar some of torque force applied to the screw serves to close the collar
to the bore. In the two-piece collar all torquing effort is available because of two screws
equally spaced on both sides of the collar.
THE TECHNICAL DETAILS
What materials are used in making collars?
Steel
Steel collars are the most commonly used. The exact type of steel used
varies depending on the machine process but generally low-carbon steel is used, including
materials such as 12L14, 1215, and 1026.
Stainless Steel
Stainless steel collars are used primarily in food processing, pharmaceutical
or marine applications or those in which components are washed frequently. Climax Premium Shaft
Collars and Rigid Couplings are made from Austenitic Type 303 stainless steel that meets FDA guidelines.
Aluminum
Aluminum collars are lighter, have the non-magnetic properties of aluminum desirable for many applications, and have a bright gleaming finish that is highly suitable for applications with high visibility. Colored or clear anodizing can also be provided as a "special" finish.
Powdered or sintered steel is not used in Climax collars because it makes a poor quality collar and cannot be welded. In sintered set screw collars, the threads tend to be weak and not uniform in performance.
What finishes are used?
Black Oxide
All steel split collars and all couplings have a black oxide finish, which is industry standard. Set-screw collars are also offered with a black oxide finish (indicated by the "-BO" after the part number).
The black oxide finish on our mild steel collars is formulated as part of the total performance of the collar. The black oxide finish affects the anti-stick-slip characteristics and helps keep the torque rating of the screw within its design parameters.
The black oxide process also has corrosion resistant properties for indoor environmental applications. However, black oxide is not intended as an outside weather protective finish. Other advantages to black oxide collars include dimensional uniformity with negligible thickness and no flaking or chipping.
Zinc Plating
Zinc-plating is the generally accepted industry standard for set-screw collars and is used on all Climax standard set screw collars (the "C"-Series), except for one line (the "C-BO"-Series) that has a black oxide finish.
This type of plating provides corrosion resistance in indoor environmental applications and has a "shiny silver" appearance for product appeal.
Special zinc-plating, often associated with different colorings, such as yellow-zinc dichromate or black zinc plating, can be applied to greatly increase corrosion resistance.
Other Finishes
Climax stainless steel and aluminum collars have a plain bright finish.
Climax offers numerous special finishes to meet particular needs. Special finishes include
anodizing for aluminum collars and special zinc-plating with greater corrosion resistance.
Is there an industry standard for collar dimensions?
While there are no formal industry standards for shaft collars, the dimensions of most
manufacturers' collars are fairly uniform. In most applications, dimensions other than
the bore are considered non-critical. Climax provides dimensions and tolerances for all bore,
outer diameter and width dimensions in our catalog. And we are always happy to quote special
dimensions as needed.
What is the purpose of the relief cut on one-piece collars?
The purpose of the relief cut is to allow the one-piece collar to close and tighten securely on
the shaft. A relief cut is important only on smaller bore collars. Climax puts a relief cut in
collars with a 1 ½" bore or smaller (under 40mm in metric and under 1 ¾-16 in threaded collars).
What is the purpose of the face groove?
The face groove on clamping collars indicates the face that should be placed against a bearing
or other component requiring a perpendicular to bore orientation. For Two-Piece collars, the
face groove also helps keep the two halves of the Two-Piece collar properly oriented.
