Bearing Separator that is Convenient to have with a Set of Bearing Pullers

The pilot bearing puller, an essential tool for replacing bearings in wheels and engines, sets the chuck inside the inner ring and pulls it out. In contrast, the bearing separator, which supports and pulls out the outside of the outer ring, is required when removing bearings incorporated in the shaft section. It is useful for removing not only ball bearings but also the inner races of tapered roller bearings and stem bearing races.

Separator that clamps and pulls up the outer ring of a bearing from the outside

The bearing separator set consists of two types of separators to be used according to the bearing outer diameter and bolts of different lengths to connect the shaft-puller. While some pullers are 2- or 3-jaw-type tools for gripping bearing outer rings, the separator features a thinner tip than the jaw type.

The separator bites into the gap between the bearing outer ring and the crankshaft web. The single-blade shape allows the gap to be widened by tightening the bolt nuts on both ends, even if the bearings are tightly fitted. If the bearing is a light press-fit bearing, it will lift up without having to press down on the center of the crankshaft with the bolts of the yardstick.

When one hears the term "tool for removing press-fitted bearings," the first thing that comes to mind is probably the pilot bearing puller. Bearing pullers, which often omit the pilot in actual tooling, insert a chuck into the inner ring of a bearing that has been press-fitted into a bore-shaped bearing housing, spread the tip to crimp it, and pull it out with a center bolt.

Wheel bearings and bearings press-fitted in the engine are pressed into the wheel hub or crankcase with the outer ring pressed into the wheel hub or crankcase to insert and rotate the axle shaft or transmission shaft, and a bearing puller is used to remove them.

On the other hand, some bearings, such as crankshafts and transmission shafts for single-cylinder and two-cylinder engines, have an inner ring that is press-fitted onto the shaft. In this case, a tool that hangs on the outside of the outer ring and pulls it up is required to remove the bearing. The tool for this purpose is a bearing separator.

The bearing separator is a two-part separator that clamps the bearing from the outside and removes the bearing by pushing the end of the crankshaft or transmission shaft with the bolt in the center of the bolted-together yagura and pulling up the separator.

The tip (inside) of the separator becomes thinner toward the end, and the center bites into the bearing outer ring by clamping the lower side of the bearing outer ring. When a flat-blade screwdriver or a hammer is used to remove a bearing that is press-fitted into a shaft, the force is applied only to the one point where the tool hits. Therefore, apart from the force in the disengagement direction, a force that tilts the bearing is applied, and the inner ring tries to bite into the shaft.

In contrast, the separator evenly clamps the outer ring at multiple points, so the bearing does not tilt against the shaft and there is less risk of damaging the part. If the bearing has a small press-fit allowance, it can be lifted off the shaft simply by tightening the bolt nuts on both ends of the separator. That is how important it is to pull it straight up.

If the crankshaft is close to the crank web and bearing, or if the transmission is close to the gear and bearing, a separator with a sharp and thin tip can be pulled up while gradually biting into it.

Specifically, when the gap on the backside of the bearing is small, the separator is hooked slightly onto the outer ring and tightened with the bolt to lift it up slightly, and when the gap opens up, the bolt nuts on both ends of the separator are tightened to make the cutting edges bite into the bearing. If you try to lift the bearing with only the sharp and thin cutting edge, the load will be too much, so you have to bite the separator deeply into the bearing to fit the gap that gradually widens.

In the case of a pilot bearing puller, the chuck inserted into the inner ring is first tightened firmly to prevent it from falling out. The separator, however, gradually increases the amount of tightening during the bearing pull-up process, thereby preventing damage to the tool and allowing it to be pulled up with a high degree of rigidity.

Extending the bolt on the separator will also help in removing the ball race at the lower end of the stem shaft

Example of using a bearing separator to pull out the inner race of a ball-type stem bearing. The separator is used to hold the inner race between the race and the stem shaft, and a set of bolts are jointed so that the length of the race exceeds the stem shaft. If a tapered bolt is used, the race tends to be pulled out at an angle, but the bearing separator is pulled out vertically, so there is less risk of damaging the stem shaft.

Depending on the position and shape of the handle stopper on the lower bracket, the separator may interfere and not function properly. In the case of this model, the separator could be set so that the stopper protrusion fit in the gap between the separator and the stopper, so it could be pulled out.

The bearing separator itself may be clamped in a vise for added stability during work. Keep your hand on the stem when tightening the yagura bolt, since the stem will come off when the inner race is pulled out.

Bearing separators can be used for other applications besides engine parts, as long as the shaft has a bearing press-fitted into it. A typical example is a steering stem bearing.

When pulling out the inner race press-fitted into the stem shaft with a tool, it is common practice to tap the race in the gap between the outer circumference of the race and the lower bracket a little at a time to raise the race. However, if you are greedy and hit one part too much in order to pull it out quickly, the race will tilt and bite into the stem shaft.

There are two types of stem bearings: ball type and tapered roller type. The ball type has a thinner race and tends to tilt more easily when it is struck up from the back.

If a separator can be used in this operation, it can be pulled straight up according to the stem shaft while holding the outer race circumference at multiple points, preventing biting and scratching.

Compared to crankshafts and transmissions, stem bearings have longer shafts and deeper so-called bosom, so the distance between the separator and the gurney is larger. In anticipation of such work, some separator sets include long bolts to connect the girders. Even if such bolts are not available, you can also use long-type Allen screws sold at home centers to support long shafts such as stem shafts.

In the image, the lower inner race of the small-displacement model is pulled out. After clamping the race with the separator, all you have to do is turn the bolt, so it was much easier to replace the bearing than to tap it with a tagger while being careful.

Note, however, that the separator may interfere with the shape of the handlebar stopper or steering lock on the lower bracket. If interference can be avoided by adjusting the position of the two-segment separator, the inner race can be pulled out cleanly.

If the shaft cannot be bolted from the top of the yagura, a separator with a bearing between it and the shaft can be fixed and pressed with a hydraulic press, or a block can be placed between the separator and the shaft and pressed with a hydraulic press.

The bearing separator, which grips and pulls up the outer circumference of the bearing to prevent it from tilting, is a tool that looks bulky but can be used for delicate work. When used for engine or body maintenance, it can be used in a variety of ways depending on the situation and ingenuity, if prepared as a set with a pilot bearing puller that grips the inner ring.