In this note, we are going to elaborate on top plates and some common sizes of top plates used in the industry. We are going to try and keep the advice short and simple by sticking with 3 series of casters which cover a broad range of common applications in the industry. Beginning with basics, a top plate is a square or rectangle plate at the top of the caster with 4 bolt holes drilled through it. These holes are where the screws/bolts are set through to meet the nut and secure the caster to the surface it is being attached to. Although top plates are ubiquitous within the industry, there are still numerous different sizes out there. These various sizes of top plates are the cause of much confusion and error in selecting the wrong caster when replacing an old pair with a new pair. Below, we will assess a few of the most common sizes and also indicate some common alternatives to make you more familiar with the options that are available in each of the three series.
Starting with the General/Light Duty caster series I want to preface this section by saying this can be the most confusing series of top plates. There are a wide variety of sizes that seem to change with wheel size along with moving from a swivel caster to a rigid caster. A common top plate size in this series is the 1-7/8” x 2-9/16” top plate with a bolt hole pattern of 15/16” x 2-1/8”. Another size that seems to be just as present is the 3-1/8” x 4-1/8” with a bolt hole pattern of 2-3/8” x 3-3/8”. However, as stated above, this is the one series that seems to change plate sizes as the wheel size gets bigger. Some common correlations are listed below: 2” Wheel – 1-7/8” x 2-9/16” 2-1/2” Wheel – 2-3/4” x 3-7/8” 3” Wheel – 3-1/8” x 4-1/8” 4’ Wheel – 4” x 5” Most wheels in this General/Light Duty series would be about 7/8” or 15/16” wide. Since this series of top plates can vary so widely, it may be best to call one of our trained caster professionals to assist you with finding the right sized top plate for your application. Moving on to the Light Duty/Institutional casters, things become much simpler from here. The most common top plate size is 2-3/8? x 3-5/8? with a bolt hole pattern of 1-3/4? x 2-7/8? slotted to 3?. Although there really is no “standard” in the industry, this would be what I consider typical size in this series. The other common option in this series would be the 3-1/8” x 4-1/8” top plate with a bolt hole pattern of 1-3/4” x 2-15/16” slotted to 2-3/8” x 3-3/8” Most wheels in this series would be 1-1/4” wide. The third and final series highlighted in this entry is the Medium/Heavy Duty caster series. This series follows suit in being more consistent simplistic in comparison with the general/light duty series. The most common top plate size in this series is the 4” x 4-1/2” top plate with a bolt hole pattern of 2-5/8” x 3-5/8” slotted to 3” x 3”. One common alternative size to this would be the 5” x 5-1/2” top plate with a bolt hole pattern of 4-1/8” x 4-1/2”. Now that we’ve highlighted a few of the most common sizes of top plates in the industry, we hope you are better able to identify which top plate you have and which top plate you are looking for. It is very frustrating when you order a caster and are unable to mount it because the top plate size is wrong. If you are having trouble identifying which size top plate is right for you or if you have any other questions call one of our experts for assistance in identifying which caster is the right fit for you!