The need to replace a linear guide in an existing machine or assembly can arise for any number of reasons: to improve the stiffness of the assembly by changing to a bearing with higher preload, or to accommodate unforeseen space constraints by using a different bearing type or style. And sometimes, a linear guide needs to be replaced simply for maintenance and repair.
Regardless of the reason for an interchange, the process of changing a linear bearing isn’t always as simple as ordering a new component and installing it on the machine. For some products, components from different manufacturers cannot be interchanged, regardless of their style or size. And even within a given manufacturer’s product line, not all components are interchangeable. Before you make an attempt to replace a linear bearing, shaft, or rail, here’s a guide to what types are (and are not) interchangeable and what dictates their interchangeability.
In this context, “style” refers to the general shape of the bearing block—its length (standard, short, or long), width (standard or wide), and whether it has flanges or not. “Style” can also refer to how many rows of balls the bearing has—two, four, or six.
Round shaft linear bearings
Round shaft versions are the easiest linear bearings to replace and to “mix and match,” because most are dimensionally interchangeable, regardless of manufacturer or style. However, load capacities may vary significantly between manufacturers and styles, due to different methods of ball recirculation, which affects a bearing’s load capacity. Adding to the options and flexibility afforded by round shaft bearings, many types and sizes of plain bearings are interchangeable with common recirculating styles.
Round shaft guides
Interchanging round shaft guides is a straightforward process, due to their simple geometry and small range of materials and hardness ratings. Their primary specifications are diameter, diameter tolerance, and shaft hardness. As long as those three parameters match, or are suitable for the application, any shaft from any manufacturer can be used with any plain or recirculating bearing of the same size.
Profiled rail bearing blocks
Due to geometric and dimensional differences in the raceways of the bearing and guide rail, it’s not possible to use a profiled rail bearing from one manufacturer with a guide rail from another manufacturer. So if only one component (either bearing or rail) needs to be replaced, it must come from the same manufacturer as the original.
On the other hand, if both components need to be replaced, it is possible, in some cases, to interchange an entire assembly from one manufacturer to another. This is because some of the most frequently-used sizes and styles of profiled rail assemblies have the same outer dimensions (height, width, mounting bolt pattern) between manufacturers.
Manufacturers sometimes use the term “random matching” to indicate that products within their profiled rail linear guide offering are interchangeable.
When changing from one profiled rail bearing to a different style or preload within a manufacturer’s product line, keep in mind that interchangeability is not always provided for in the design. This is because in order to “mix and match” different bearing blocks and rails of a given size, the positions of the raceways on both the rail and the bearing block must be very precisely controlled. Very often, preloaded bearing blocks are not interchangeable, because tolerances between the guide rail and the bearing affect the preload amount.
Profiled rail guides
In the same manner as profiled rail bearing blocks, profiled rail guides are not interchangeable between manufacturers. However, within a manufacturer’s product line, profiled rail guides can typically be interchanged, as long as they are of the same style—meaning the number and design of the raceways is the same.
Several manufacturers have developed interchange tables or web-based interchange tools, which can be found in our list of interchange tools for linear guides and bearings.
Leave a Reply
You must be logged in to post a comment.