With tapered roller bearings, the terms “setting” and “fitting” are interchangeable. They both serve the same function and purpose. But regardless of the terminology used, the process is still the same. And this process is what many businesses and clients with machinery that requires this type of equipment have questions about. To help with the basics, here are a few facts about these types of bearing and their various settings:
A setting or fitting simply refers to the amount of axial clearance (endplay) or axial interference (preload) within any given mounted bearing. Setting is more specifically defined as the axial clearance between raceway and roller. Creating the setting during the time of assembly is one of the many advantages with tapered roller bearings. They can be adjusted to provide optimal performance in virtually any application.
Unlike a number of other kinds of anti-friction bearings, tapered roller bearings are not strictly dependent on shaft fits or housing to achieve a specific bearing setting. A single ring can be moved to create the intended bearing setting.
Assembly Bearing Settings
During the assembly process, the bearing settings are set to the manufacturing recommended and/or engineering specifications. There will nearly always be some play involved once the bearings are installed and in operation at a later date. But before that comes, the assembly conditions for these bearing settings are defined as so:
Endplay (EP) – This is the axial clearance between rollers and raceways producing a readable shaft movement of the axial when applying a small amount of axial force. This action begins in one direction, then shifts to the other, while rotating or oscillating the shaft.
Preload (PL) – This refers to the axial interference between raceways and rollers in that there is no definable shaft movement of the axial when applying that same small amount of force as with endplay. Only this time the force is applied in both directions, all while still rotating the shaft as well.
Line-to-line – This is what is known as a zero-setting condition: the point of transition between preload and endplay. Whatever bearing setting is applied during the initial assembly process and adjustment is the ambient or “cold” setting. This is always established before the equipment is installed or designated into service.
Operating Bearing Settings
After the bearings have received their factory settings during the assembly process and go on to be installed in various types of machinery, the next step is establishing what is known as the operating bearing settings. These are necessary for a number of reasons. Specific examples include fluctuations in temperature, which affect the ambient bearing setting, as well as other deflections which may be encountered during usage and service time. To define it specifically would be to say it is the exact yet undetermined setting necessary to for the equipment to operate at optimal levels. Of course, that particular setting will vary with different equipment and applications.
What generally determines the best operational settings is specialized testing or previous experience with the same equipment and/or machinery. But many times still, the specific prime setting for ambient to operating is simply unknown and deductive reasoning and educated guesses have to be made. Contacting a specialist in the area for tapered roller bearings in Harrisburg, PA would be a good help. </span
Ideal Operating Bearing
Where possible, a setting near zero to maximize operational life is recommended. Most endplay assembly settings are designed to achieve the preferred near-zero setting at functional temperature. There is a similar setting value for other bearings and for every application.
To achieve the necessary conditions, the estimated setting must consider the amount of deflection under load (axial + radial) as well as various materials involved in operations, thermal expansions and material used, and numerous complex mathematical equations. The temperature fluctuations and expansions, and still other fitting effects will depend upon the mounting type, housing and shaft size, dimensional parameters, bearing size and geometry and size, among many other factors.
Upper and lower limits
These two separate bearing setting values are influenced by a number or factors as well. One of the main determiners of what those limits can be is what type of machine or equipment application they are servicing. Another is how heavy and how frequent its workload is. Variations in temperature can also impact the bearing settings. The method and frequency of lubrication is another factor. So is the size of the bearing itself and how the initial setting was acquired. The sturdiness and functionality of the housing and shaft material surrounding the bearings also play a role.
And even still, any other changes or shifts that occur during operation will also have to be factored into determining lower and upper limits as well. Again, it is always best when you can speak to local experts on tapered roller bearings in Harrisburg, PA concerning such specific machinery and operating parameters for this type of equipment.