Why would I use a Simplicity plain bearing instead of the linear ball bearing I’ve always used?
There are multiple advantages that the Simplicity linear bearing with a FrelonGold liner has over linear ball bearings, but there are two that stand out the most. First, they are self-lubricating or do not require additional grease and oil to be added to operate properly. Linear ball bearings require grease to be used. Secondly, the Simplicity plain bearings handle contamination extremely well by creating a natural seal on the shaft and pushing the dirt, dust, chips, and other contaminants to the end of the stroke. Linear ball bearings must have added seals that often allow particulate to slip past and into the raceways where it will catch in between the balls and stop them from rotating which leads to failure.
Why would I use a linear ball bearing instead of a plain bearing?
There are two main reasons you might want to consider a linear ball bearing over a plain bearing. First would be that they have a low coefficient of friction meaning the balls will roll more freely than the surface of a plain bearing will slide. This will result in the ball bearing being better suited to higher speed applications. Second would be in places where a preload is required. In other words, the balls can be slightly “squeezed” by the casing around the bearing and the “play” between the bearing and shaft is removed. These bearings might be used where more precision may be needed.
Do all plain Bearings have a removable plastic insert?
The short answer is no. The term “plain bearing” applies to any bearing that does not have rolling elements, but instead is made up of a solid surface that slides along the shaft or raceway. The bearing surface could be plastic, bronze, or other polymer-based materials. PBC Linear Frelon and FrelonGold were specifically developed through intensive tribological testing for linear motion applications. Also, note that these materials from PBC Linear are not inserts, but rather the material is boned permanently into place with a structural adhesive similar to how airplane wings are bonded together creating a one-piece bearing.
How do you mount linear bearings in place?
The easiest way is to purchase them already mounted in standard pillow blocks where they are fixed in place with retaining rings and/or a pin. If standard pillow blocks are not an option, you could create your own housing and retain the bearing at the ends with retaining rings or bore the housing to specification and then press fit the bearing. Instructions for bearing installation can be found in the RST catalog here: Catalog
What linear bearings will stand up to harsh chemicals?
In general, stainless steel jacketed bearings will hold up the best in harsh chemicals, and many polymer-based materials can be chemically inert. It is always best to check with a specific manufacturer on chemical compatibility. PBC Linear bearings Chemical Reaction Chart can be found here: Chart
What are the grooves on the outside of a linear bearing for?
The smaller grooves toward the ends of a linear bearing are designed for retaining rings that can hold the bearing in a housing. The larger inner grooves on Simplicity linear bearings are for O-ring’s that will help cushion slight movements when used in a self-aligning pillow block.
What happens when I put a cantilevered load on a linear bearing?
Both plain bearings and linear ball bearings will work in cantilevered load applications, but keep in mind there are consequences for each. With a plain bearing, the load must stay within the 2:1 ratio or the bearings will bind causing stick-slip or possibly locking up the motion. Linear ball bearings may continue to operate beyond the 2:1 ratio, but keep in mind that the balls will be causing increased point pressure on the shaft resulting in galling and severely shortened life. You can learn more about the 2:1 ratio here: Video
How can I handle a cantilevered load in my linear motion system?
Cantilevered loads are inevitable in linear motion systems, but there are things that can be done to minimize their effects on the bearings. One of the most important things is to spread the bearings as far apart as possible to lower the moment loads. A counterbalance can possibly be added to offset the overhung load. Or in some cases, a single outrigger rail can be added away from the main system to help support or offset the cantilever.
Are not all linear bearings imported into the USA today?
No, PBC Linear is committed to manufacturing in the USA and has a 50-acre campus with over 250,000 square feet of production space where approximately 100 machines keep their spindles turning to produce millions of bearings each year.
Can I use a linear bearing in a pivoting or rotary application?
You cannot use a linear ball bearing in a pivoting or rotating motion due to the arrangement of the balls in the raceways. However, because a plain bearing like Simplicity has a solid gliding surface for the bearing, it can move in any or multiple directions at the same time.
What sort of life expectancy can I anticipate from a
PBC Linear plain bearing?
There is no known formula for accurately and reliably predicting the life of a plain bearing because there are too many dependent variables.
What is the expected life of Simplicity® plain bearings?
Bearing failure is subjective and dependent upon specific application requirements. There are many factors within an application that can affect wear to different degrees. While not an all-inclusive list, some of the most important issues to address are discussed in the Round Shaft Technology catalog:
What is the coefficient of friction (C.O.F.) for Simplicity plain bearings?
The coefficient of friction for filled Teflon can range from 0.125 to 0.4 depending on the fillers used. FrelonGOLD has an average COF of 0.125, while Frelon J has an average COF of 0.12.
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