Expanding adapters are a hybrid design, utilizing a threaded stem with a flexible socket adapter. Typically they are constructed with 4 parts: a threaded stem, a compression nut, a rubber expansion ring, and a plastic washer. In essence, they are a hybrid of a grip ring and threaded stem. In as much as they do not require special machining of the equipment, but no socket is required.
Usually, these stems are used on equipment where a standard socket is not available because of the inside diameter of the round tube or pipe. They are installed by inserting the stem into the pipe and then turning the nut on the bottom side of the swivel section to tighten into place. A pretty simple installation, which also provides for an equally simple removal.
These stems are not indicated for use on equipment subject to large amounts of moisture and heat, such as wash-down or autoclave situations. This is because the rubber insert can dry-rot. Once the rubber has dried out the caster may, for lack of a better phrase, fall out of the equipment. The exposure to moisture hastens the natural decay of the rubber, therefore failure will be premature. When considering an expanding stem for an application, consider a grip ring or a threaded stem first if the equipment will be in a wet or rough situation, they typically provide a more positive retention mechanism.
Overall, an expanding adapter provides a flexible alternative to more fixed methods such as grip rings and threaded stems. Implementing them on equipment can help avoid additional manufacturing or assembly time. With that in mind, there are some noted limitations, as mentioned previously. Contact us for help in deciding the correct mounting for your application.