A ball bearing that supports the shaft of a component that rotates at high speed is a component that can be used for a long time as long as it is properly lubricated and no dust or foreign matter gets into the rotating part. When replacing such a ball bearing, either the outer or inner ring must be pressed in. When pressing the outer ring into the hole in the housing, use an insertion tool that can press the outer ring firmly.
Sometimes heat can be used to set the bearing without a press fit.
The image shows a motorcycle bearing installer made by HASCO, a manufacturer specializing an exclusive tools for motorcycles and automobiles. It features a set of plates that match the bearing sizes often used in motorcycles, and is strong enough to be used with a hydraulic press.
The outer periphery of the attachment is rimmed so that only the outer ring of a ball bearing or the outer diameter of an oil seal can be pressed. Two plates can be stacked on top of each other, so if there is a plate that matches the inner diameter of the bearing, it can be used to stop the installer itself from shifting.
Ball bearings built into various parts of motorcycles and automobiles can be used for quite a long time if they are handled properly. For example, wheel bearings in automobiles can be used even when the mileage reaches 500,000 km or more without any problems.
The major causes of failure of such long-lived bearings are poor lubrication, contamination by foreign substances, and shock. Bearings built into the engine are lubricated by engine oil, while bearings that cannot be lubricated externally, such as wheel bearings, are lubricated by sealed grease. If the lubrication is inadequate for some reason, heat builds up in the contact area of the ball between the inner and outer rings, causing seizure. Dust and debris can also get into the rotating parts, damaging the parts where the balls roll and causing damage.
The bearing has either an outer ring or an inner ring that is press-fitted into the housing, and must be pulled out with a puller to be replaced. If the ball bearing is press-fitted in the housing (hole), insert the puller into the inner ring and pull it up; if it is press-fitted in the shaft, hook the puller on the outside of the outer ring and pull it up. If the bearing is poorly lubricated, sticking, or feels uncomfortable when turned, you are free to remove it as long as you do not reuse it.
However, care must be taken when press-fitting a new bearing. When pressing into a housing, the outer ring must be pressed with uniform force, and when pressing into a shaft, the inner ring must be pressed with uniform force. If this is reversed, extra force will be applied to the inner ring, outer ring, and ball contact area, and there is a risk of scratches and indentations on the ball raceway.
Special installers are available to press-fit bearings, but in some cases heat can be used to mount bearings without using an installer. For example, if you are installing bearings in a crankcase that is divided into left and right sections, such as the Honda Monkey series, you can use a heater to expand the case, and the bearings at room temperature will easily fit into the housing. When installing bearings in a shaft, boil the bearings in heated oil to expand them, then insert them into the shaft at room temperature for a smooth installation.
When heating the housing, it is important to evenly distribute the temperature over the entire housing, and when heating the bearing itself, sealed bearings with grease cannot be used.
POINT
POINT 1: When press fitting a ball bearing, there are two cases: press fitting into a hole and press fitting into a shaft.
POINT 2: By using metal expansion caused by heat, it is sometimes possible to assemble the bearing without tapping it.
Unexpected accidents caused by socket substitution
It is easy to tap the bearing with a socket, but depending on the processing and plating of the end face of the socket opening, it may damage the bearing or cause problems such as getting stuck in the housing and not being able to be removed.
A tool to tap only the outer ring is required to press-fit the ball bearing into the housing, and sockets are often used instead of exclusive bearing installers. At first glance, a socket with a small outer diameter in relation to the hexagonal part (i.e., a thin wall thickness) looks ideal as a tapping tool, but it has some inconveniences because it was not designed as a press-fit tool in the first place.
First of all, in the case of a chromiumplated socket, there is a possibility of the plating cracking and fragments getting into the raceway. It is also possible to injure your hands and fingers when using a socket with broken plating for its intended task.
The next problem is that the outer ring diameter and the outer diameter of the socket are not exactly the same size, causing the socket to bite into the housing. It would be nice if there was a socket that could provide enough clearance for the inner diameter of the housing, but since sockets are not designed to hold bearings, we can't complain.
If you want to do the job correctly, it is safer to prepare an installer.
POINT
POINT 1: Using a socket as a press-fit tool is only a substitute and may cause various problems.
The fit of the special tool is clear after use.
When press fitting the bearing into the crankcase by tapping only the outer circumference with the bearing installer, there is no need to tap any further because when the bearing reaches the bottom of the housing, a resonant sound is heard throughout the case.
The product description states that the attachment diameter is set for a universal size, but of course it was designed with the outer diameter of a standard ball bearing in mind. 6201 size has an outer diameter of φ32mm, and a φ32mm plate fits perfectly.
If the socket bites into the housing of a wheel bearing that uses an oil seal, it may damage the oil seal mounting surface. Also, if the chromium plating of the socket breaks off and gets mixed in with the raceway, the inner ring may lock up. In contrast, the installer of the exclusive tool is dyed black, so the surface will not crack and will not interfere with the housing.
Once the bearing reaches the bottom of the housing, the press fit is complete. When inserting the distance collar and press fitting the bearing on the other side, adjust the amount of press fit so as not to press out the inner ring.
There are several types of bearing installers, such as those that primarily press on the outer ring or those that press on the outer and inner rings simultaneously. Regardless of the form, however, the outer diameter of the installer is usually designed to match the outer diameter of a common ball bearing, so it will not bite into the housing during press fitting.
Also, the handle is thicker than the attachment that contacts the bearing, which makes it difficult to tilt when striking with a hammer or press fitting with a hydraulic press. Incidentally, even if the bearing is at an angle to the housing, you can still get it in to some extent by tapping it with a hammer. It is possible that the outer ring may have scraped the housing before you realize it, so even if you use an installer, you need to be especially careful when adjusting the angle at the entrance.
The installer used here has a feature that the outer edge is raised to contact only the outer ring of the bearing. It can also be flipped over to hold the outer and inner rings at the same time.
If you are a rider who enjoys riding on the street or touring, you may want to have a professional replace the bearings if you feel any discomfort or if they are pointed out to you by a motorcycle shop. On the other hand, for riders who prefer to tinker with their mtorcycles by themselves, it is important to choose a tool that reduces the risk of failure. From this perspective, an installer that press-fits ball bearings into housings is a very effective tool.
POINT
POINT 1: Using a bearing installer improves the accuracy of tapping the outer circumference of the bearing and pressing it into the housing.
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