How To Determine Bearing Shaft And Housing Fit

Determining the bearing shaft and housing fit is an important decision to make. It helps you optimize your machine performance and expanciate the lifespan of your machinery. This article will guide you on how to determine the bearing shaft and housing fit.

Types Of Bearing Shaft And Housing Fit

The word “Fit” simply means the relation between two mating components, and it relates to how tight or loose an item should be when they are joined together. There are three referenced types of fit in manufacturing and mechanical engineering.

Clearance Fit

Clearance fit gives room to free movement between the bearing bore and the shaft, or outer ring and housing. These types of fit are mostly preferable where it is necessary for elements to go in and out of their mating component without any stoppage, and where alignment can be gently guided but does not necessitate strict precision. One good example of clearance fit is bolt/shaft holes that permit one element to slide freely through another feature.

Interference Fit

Another name for interference fit is press fit or friction fit. It requires more tightness to join two components compared to clearance fit. A typical example of how interference fit works is when you press a bearing, dowel pin, bushings, or other items into their mating parts, that is why it’s also called press fit. Once these components are joined, there’ll be a relatively hard union between the components that only a significant force from machines can uncouple.

Transition Fit

Another name for transition fit is push or slip fit. It’s in between a clearance fit and interference fit. This type of fit is the most suitable when a precise alignment is important and when top-notch accuracy is needed in the process of joining the mating piece. When you are using transition fit for your mating piece, there will be more space left compared to when you are using other types of fit. Although the spaces will be minor it should suspend excess movement in the joint.

Steps For Determining House Fit

Inner ring rotation and a constant radial load are used mostly in general applications. In situations like this, it’s a good decision to use an interference fit between the shaft and the bearing bore. When there are heavier loads the interference level will rise. In addition, a clearance fit between the shaft and bearing bore is a good recommendation when the radial load is constant and shaft situations are stationary. Additionally, below are other steps for determining house fit:

1. Identify the load direction, the operating speed, and the operating condition of the bearing. Additionally, understand if the load is axial, radial, or combined load.
2. Consider the bearing size and type because the different bearing sizes and types have their actual fit recommendations.
3. Calculate the tolerance you need for the housing and shaft depending on the fit type.
4. Be conscious of the thermal expansion of the shaft and housing that is capable of affecting the operational factors.
5. It might be necessary for you to adjust if there are special operating conditions like high speed or temperature.

How To Select The Proper Housing Fit

To select the proper housing fit consider the load type, the installation process (whether it’s easy to install or remove), and the rotation of the outer or inner rings. Additionally, the rotation of the bearing’s inner ring and its relationship to the radial load are the primary factors to consider.

How To Apply Theory To A Sample Situation

For example, when you are to install a bearing in an electric motor application, first look at the application specifics. In situations like this, the outer ring is stationary, the load applied is constant, and your inner ring will rotate.

Now, the shaft will be 20mm with a 6204 ball bearing (0.787402″ x 1.85039″)(I.D x O.D). The above measurement indicates that the inner ring is the one rotating, an interference fit is what you need on the shaft. The type of fit that is most suitable for the housing bore is transition fit because it gives room for easy installation and removal.

Factors To Consider Before Determining Bearing Shaft And Housing Fit

Determining the actual bearing shaft and housing fit for your application is an important decision to make because it facilitates optimal performance and longer service life in your machinery.

Meanwhile, size and type of bearing, running accuracy requirement, operating temperature, material composition and machining tolerances of mating components, and the type and amount of load are factors to consider before determining bearing shaft and housing fit.

FAQs

What Happens If The Bearing Shaft And Housing Fit Is Too Tight Or Too Loose?

When your bearing shaft and housing fit is too tight there will be metal contact between both components, thus leading to shaft wear and bearing overload. Why too loose of a bearing and shaft housing fit will lead to corrosion of the shaft and bore, excessive vibration and noise, poor bearing rotation, and excessive wear.

Conclusion

Selecting the actual bearing shaft and housing fit will give optimal bearing performance, prevent premature failure, give smooth operation, and optimize load distribution. Operational loads, materials, bearing type, and environmental conditions are important factors to consider.