Jaw Couplings
Jaw Couplings are one of the first and still most widely used elastomer couplings in the world due to their inherent simplicity. Two identical hubs with 3 face lugs are connected through a star shaped element, sometimes referred to as an insert or spider. The 3 piece design makes them simple to work with and popular on applications such as pumps, fans, blowers and compressors.
Jaw Couplings require no lubrication and provide high reliability for light to medium duty applications with good alignment of equipment and no requirement for torsional dampening.
In normal operating conditions there is no metal to metal contact so the life of the hubs is virtually indefinite. However, in a catastrophic failure of the element the load would still be carried by the hubs providing a degree of failure protection. Jaw couplings are resistant to oil, dirt, moisture and grease.
Specific element materials are available to achieve maximum performance for the operating conditions.
The standard element material is NBR (N)-'Synthetic Rubber'. It is highly flexible, oil resistant and the torsionally softest of the element options. It has a temperature operating range suitable for most industrial applications and allows for up to 1 degree misalignment capacity of the connected shafts. NBR is the most economically priced option.
Urethane elements, abbreviated as type U provide a torque range 150% of NBR with an added resistance to many chemical compounds.
Hytrel(H) elements are a popular option for high torque or high temperature application. They can carry 2-3 times the torque of the NBR elements for an adder safety factor or smaller coupling size selection. Due to the stiffer and harder material utilized they are not as flexible and misalignment capacities are about 1/2 of NBR. Hytrel elements sell for about 3 times the price of NBR but still may provide an overall price advantage due to smaller coupling sizes that may be used.
The fourth element option is a Bronze (B) material which is oil impregnated. It provides similar torque capacity to Hytrel while being very resistant to oils and chemicals. It also has the greatest temperature operating range but is limited to low speed applications. Bronze elements tend to be the most expensive option and limited to special applications.
See the summary chart below.
| Properties | Buna-N (N) | Urethane | Hytrel (H) | Bronze (B) |
|---|---|---|---|---|
| Oil Resistance | Good | Good | Excellent | Excellent |
| Chemical Resistance | Poor | Good | Excellent | Excellent |
| Flexibility | Excellent | Good | Fair | Poor |
| Temperature F | -40 to +212 | -30 to +160 | -60 to +250 | -40 to +450 |
| Range C | -40 to +100 | -34 to +71 | -51 to +121 | -40 to +232 |
| Torsional Stiffness | Full Soft | Medium Soft | Hard | Hard |
| Average Hardness (Shore Number) | 80A | 90A | 55D | - |
| Max. Misalignment | ||||
| • Angular | 1° | 1° | 1/2° | 1/2° |
| • Parallel | 0.15" | 0.15" | 0.15" | 0.10" |
| Color | Black | Orange | White | Bronze |
| Cost | Lowest | Moderate | Higher | Highest |
The elastomer element is designed to be the sacrificial component of the coupling and should be replaced when wear due to shaft misalignment or surface compression takes place reducing the thickness of the element to 75% of original.
MasterDrive's L-Series Jaw couplings are available to cover shaft sizes from 1/2" to 2 5/8" and torque ranges up to 6,228 in. lbs. @ all common motor speeds.
Chemical Resistance Table can be viewed here.
Dimensions for all Jaw Couplings can be found here.
Stock bore sizes for all Jaw Couplings can be found here.
A standard bore and keyway tolerance table can be found here.
Jaw Coupling Selection can be found here.
