Caster Mounting Types
Plate casters are attached to rolling equipment with a flat rectangular plate that has 4 bolt holes in the corners of the plate. They are bolted or screwed into place. When ordering, three measurements are important: (1) the bolt hole pattern (the distance between the centerlines of the bolt holes); (2) the outside perimeter dimensions of the plate; and (3) the size of the bolt holes themselves. The bolt hole pattern is the most important measurement.
Grip ring casters are used on rolling equipment with legs made of hollow tubing or pipe. The caster has a round stem fitted with a metal expandable ring that rides in a groove machined around the circumference of the stem. When ordering such a caster it is important to accurately measure the internal diameter (ID) of the tube. The ID of the tube should be just a little larger than the OD of the stem. When the caster is forced into the leg the metal ring, which is a little larger than the ID of the tubing, is compressed tightly against the inside of the leg. This compression is what holds the caster in the leg.
Expandable stem casters are used in roughly the same applications as grip ring stem casters. The stem of the caster is threaded, and over the stem is a plastic spacer, a round rubber applicator, and a knurled nut at the top. When the knurled nut is tightened on the stem, the rubber applicator is compressed vertically, causing the applicator to expand out against the inside of the tubing. This locks the caster in place inside the tubing. When ordering it is important to measure the ID of the tubing accurately. The virtue of this caster is that with the eight different applicator sizes we stock, it can be made to fit all sizes of tubing from 3/4” up to 1-7/8”.
Threaded stem casters are used on many different kinds of equipment. The caster has a round threaded stem that is bolted on to the equipment . When ordering three dimensions are important: (1) the diameter of the stem; (2) the length of the stem; (3) the number of threads per inch. The size of threaded stems is signified by a set of dimensions such as ‘1/2-13 x 1’. This means 1/2” diameter, 13 threads to the inch, and 1” long. To determine threads per inch simply measure with a ruler and count the number of threads in an inch.
Stemless or hollow kingpin casters are used in applications similar to those in which threaded stems are used. This caster has a 3/8” or 1/2” hole up through the swivel assembly of the caster. Instead of a permanent threaded stem, a standard bolt is run up through this hole and bolted on to the equipment. The virtue of this caster is that it can be used with virtually any size stem, including metric sizes, up to 1/2”.
Octagonal stem casters are attached to rolling equipment with an octagonal stem that is 2” long and 3/4” across the flat sides of the stem. This caster is used almost exclusively on equipment with angle iron legs. The opposing flat sides of the stem form a 90° angle that fits inside the angle iron. Two 1/4” holes spaced 1-1/4” apart on one side of the stem and a single 1/4” hole in the middle on the other side are used to bolt the caster to the legs.