Retaining compounds are a type of adhesive first invented in the 1960s. They are used to fill the spacing between mechanical components, as well as installing the bearings inside houses, shafts and retaining cylinder liners. Once cured, they provide a strong bond between the components to give the final product a high-precision assembly.
Why Use a Retaining Compound?
As adhesives, a retaining compound can be used alone or in combination with various mechanical methods. However, they are more commonly used to fill the spacing between components because they allow for the transmission of significantly higher loads, which is beneficial to the entire assembly.
For example, the connection on a typical bearing might be secured by a press fit. The metal-to-metal contact area between the components is only 30 percent of the entire joint surface area. As a result, small movements at the joint interface will grind down the parts and produce small particles from abrasion.
Using adhesives specially designed for bearings can help to eliminate this problem. By effectively sealing the joints, micro movements are eliminated to prevent any component damage to the system. In fact, additional tests have shown that the axial strength of a component is increased three times with the application of a retaining compound at the joint.
Benefits of Using Retaining Compounds
Although retaining compounds are commonly used on bearings in housings or on shafts, they have a wide range of other applications and benefits. These applications include holding gears and pulleys onto shafts, retaining cylinder liners, fixing oil filler tubes in castings and restoring the accuracy to worn machine tools.
Retaining compounds help prevent the distortion of the metal components when used to secure bearings. Simply apply the retaining compound to the outside of the bearing before it is inserted into the casing, so any gaps between the bearing and the housing are sealed. The retaining compound protects both components from regular wear and tear.
How to Choose the Right Retaining Compound
Like all other glue products, retaining compounds come in many different types, each designed for a specific use. Some popular retaining compounds are designed to fill gaps; others offer high strength, and some have faster cure speeds.
Retaining compounds used to fill gaps between various mechanical parts are designed to have different viscosities. For example, low viscosity retaining compounds have viscosities around the 1,000 mPa*s range, and can be used for gaps that go up to 0.15 mm. To seal gaps greater than this, retaining compounds with higher viscosities, usually greater than 2,000 mPa*s, should be used instead.
Retaining compounds designed to have higher strength are ideal for applications that require a permanent bond. For example, parts that should not be taken apart during the life cycle of a device or structure should be fixed using a retaining compound with high-bond strength. For parts that need to be taken apart for occasional maintenance, retaining compounds with a lower bond strength should be used to allow for easy disassembly.
Retaining compounds with faster cure speeds are ideal to use on production lines requiring fast production rates. The retaining compound can turn rigid faster to allow for bonding to happen between the components. Fast-curing retaining compounds should not be used for applications that require minor adjustments to be made after assembly.
Popular Retaining Compounds
Like with all other products, there are popular retaining compound brands that have built up a superb reputation from years of customer satisfaction. Two of these brands are ASI and Vibra Tite.
The ASI Torque 80 RC Short Open Time High Strength Retaining Compound is a retaining compound designed to withstand torque, which is a twisting motion common in many mechanical components. They can fill gaps up to 0.015 inches and can withstand temperatures from -60 to 450°F. They are great for sealing threads and for applying to cylindrical components.
The Vibra Tite 538 High Strength Retaining Compound is a high-strength retaining compound designed to provide a sturdy and robust bond. It is made up of an anaerobic resin, which requires a lack of oxygen to work. They can withstand temperatures up to 300°F and can be used for general sealing purposes, such as locking keys and splines and restoring worn assembly parts.
Final Thoughts
Retaining compounds are adhesives commonly used to fill gaps between various mechanical components. They help prevent the distortion of these mechanical components by reducing wear and tear and increase the strength of the final assembled product. Some popular retaining compound brands include ASI and Vibra Tite, which come in different types designed to have various properties, such as temperature resistance or high strength.