Restoring the bearing seat in the housing. Method for restoring seats of rolling bearings How to seat a bearing in a broken seat

Landings

The Importance of Proper Fit

If a rolling bearing with an inner ring is only mounted on the shaft with an interference fit, dangerous annular slip may occur between the inner ring and the shaft. This sliding of the inner ring, called "slip", causes the ring to move hoop-wise relative to the shaft if the interference fit is not tight enough. When slippage occurs, the fitting surfaces become rough, causing wear and significant damage to the shaft. Abnormal heating and vibration may also occur due to abrasive metal particles penetrating the bearing.

It is important to prevent slippage by securely fastening with sufficient tension the ring that rotates, either to the shaft or in the housing. Slippage cannot always be eliminated by axial tightening through the outer surface of the bearing race. however, as a rule, there is no need to provide tension on rings subjected only to static loads. The fit is sometimes made without any interference on both the inner and outer rings to accommodate certain operating conditions or to facilitate installation and disassembly. In this case, lubrication or other applicable methods should be considered to prevent damage to the fitting surfaces due to slippage.

Loading and landing conditions

Load application	Bearing operation		Load Conditions	Landing
	Inner ring	Outer ring		Inner ring	Outer ring
	Rotational	Static	Rotational load on inner ring, static load on outer ring	Interference fit	Loose Fit
	Static	Rotational
	Static	Rotational	Rotational load on outer ring, static load on inner ring	Loose Fit	Interference fit
	Rotational	Static
Load direction not detected due to direction change or unbalanced load	Rotational or static	Rotational or static		Interference fit	Interference fit

Fit between radial bearings and housing bores

Notes on the table:

1. This table applies to cast iron and steel housings. For cases made of light alloys, the fit should be tighter than in this table.
2. Not applicable for special landings.

Fit between radial bearings and shafts

Note: This table applies to solid steel shafts only.

Restoration of bearing seats using metal polymers using the gluing method.

The essence of this method is that the process of restoring the seat is combined with the assembly operation of the bearing assembly. As a result, a stationary connection between the bearing and the shaft (bearing housing) is formed, which is many times superior in its strength characteristics to the interference fits recommended in such cases, which more reliably protects the bearing rings from turning, eliminating wear and ensuring more reliable operation of the unit. At the same time, gluing, unlike an interference fit, does not lead to stress and deformation of the bearing rings, which also contributes to more comfortable operation.

To disassemble a bearing assembly restored in this way, it is necessary to heat the metal-polymer layer formed at the gluing site to a temperature above 300 0C or burn it out, for example, using a gas torch.

The main stages of the process of restoring seats using gluing.

I.Restoration of seats with insignificant (up to 0.25 ÷ 0.3 mm in diameter), uniform wear (without preliminary mechanical treatment of the restored surface).

1. Prepare the surface to be restored in accordance with general recommendations (clean from dirt, oil, etc., roughen with sandpaper, degrease).

2. Wipe and degrease the bearing seating surface.

3. Carry out a check assembly: the bearing should be installed in the seat quite easily, without significant effort.

4. Protect the bearing cage with adhesive tape or electrical tape from possible metal polymer getting into it when gluing.

5. Prepare the required dose of metal polymer.

6. Apply the required layer or layers of metal polymer to the shaft (housing) seat, thoroughly wetting the surface to be restored.

7. Coat the bearing seat with a thin layer of metal polymer, literally wetting it.

8. Install the bearing onto the shaft (into the housing), carefully pressing it against the limiting collars, bushings, and retaining rings.

9. Remove the squeezed out excess metal polymer, clean unprotected areas on the shaft (in the housing) with acetone if metal polymer accidentally gets on them, remove the protection from the separator.

10. After polymerization of the metal-polymer, the assembly is ready for further operation.

Note:

With the indicated wear values, centering of the bearing relative to the shaft (housing) during the gluing process is ensured both by particles of metal-polymer filler falling into the gap, and by additional methods, for example: preliminary punching of the restored surface (usually it is enough to punch the surface that is the supporting surface during gluing), centering relative to other parts etc.

2. Restoration of seats with minor (up to 0.1 ÷ 0.15 mm in diameter) wear.

When restoring by gluing the seats of shafts (housings) with a wear amount of less than 0.1 ÷ 0.15 mm in diameter (the size of the gap is commensurate with the size of the filler particles), it is necessary to pre-bore the seat by 0.5 ÷ 1.0 mm, with by cutting “ragged threads” or grooves. To ensure that the bearing is centered during gluing, boring is carried out leaving bands along the edges of the seat and along its length (the total width of the bands should not exceed 50% of the entire gluing surface) - see Figure 1.

font-size:11.0pt;font-family:Arial">Fig. 1. Restoring the seat on the shaft using metal polymers by gluing the bearing:

D nom. – d 1 = 0.1 ÷ 0.15 mm;

D 1 – d 2 = 0.5 ÷ 1.0 mm;

I – places where “ragged threads” or circular grooves are cut.

The remaining stages of recovery are similar to operations in point 1.

3. Restoration of seats with significant (over 0.5 ÷ 1.0 mm in diameter) and uneven wear.

When restoring seats with significant and uneven wear using the gluing method, the issues of centering and ensuring the alignment of the bearing and shaft (bearing housing) are of particular importance. These problems can be solved in the following ways.

1. On the worn surface along the forming lines, metal spacers of varying thickness are installed (approximately 0.05 ÷ 0.08 mm thinner than the wear in this place) in the form of narrow metal strips that are longer than the wear site. The free ends of these strips are secured with adhesive tape, thread, etc. near the place of gluing (preferably on a section of the shaft with a smaller diameter). A control installation of the bearing is carried out (the bearing should be installed in the seat quite easily, without significant effort). After this, a metal polymer is applied to the place of wear (the places under the gaskets are also coated). The bearing is installed. After polymerization of the metal-polymer, the leading ends of the spacers are cut off.

2. Small diameters are applied to wear areas by welding. point(to avoid overheating of the shaft) sagging in the form of rings. After this, they are machined to the nominal bearing diameter. The bearing is being inspected. After this, gluing is carried out according to the schemes described above.

3. On worn surfaces, a groove is made to install two or more centering rings. Rings (split) are fixed in prepared grooves by welding or gluing using a metal polymer. The installed rings are machined to the nominal bearing diameter. Next, gluing is done according to the schemes described above.

Other methods of centering the bearing can be used in the process of restoring the seat by gluing using metal polymers.

Attention!

When restoring bearing seats by gluing in, before applying the metal polymer, it is necessary to protect the existing oil channels with adhesive tape or tape.

I think many have seen the unconscious cries of “Yes, these hubs are rubbish, the bearings will soon be hanging out in them!” Such school nonsense is heard every day and constantly, with or without reason.

So, we will talk about the seats of the wheel bearings and why the seats sag.

The first reason, independent of the owner, is the original quality of the materials from which the hub is made.

For example, let's take CNC hubs and a regular standard hub for budget pit bikes for comparison.

The second reason - mixed - is wheel bearings. It is mixed in the sense that it depends both on the quality of the installed bearings and on the laziness of the owner to monitor their condition.

If you install cheap bearings, they will either quickly fall apart and begin to beat, or even when new they will have a runout that is unacceptable for use in principle. Naturally, all the impacts will be transmitted to the hub, and any metal will be deformed by the impact, so that’s the subsidence.

Well, the owner is to blame in two cases: installing cheap bearings and untimely replacement of the bearing, it’s simple.

The third reason is an overtightened drive chain. It puts a large load on one side of the wheel, and accordingly, uneven distribution of loads leads to beating, accelerated wear, impacts - and that’s it, the landing sag.

BUT ALL THIS IS NOTHING compared to the main reason - HANDMADE!)))

There is simply a realm of engineering idiocy here.

So, the first chapter is knocking out bearings with a screwdriver and a sledgehammer on a cold one! This is exactly what every schoolchild loves. After he does this, microns of metal are removed by a bearing coming out crookedly, but this is nonsense. They also don’t hit in a circle, knocking out the bearing evenly, but instead hit at one point. In this case, the bearing rests on one side, sinks the hubs, and even removes the necessary microns with its edge!

Let's say some people think that heating the metal is not necessary, and that an anchor puller is enough. Even so, the bearing will at least move evenly, but it will be tight, and microns will still be eaten away, and this is not good. But why do you need pullers and hair dryers? There is a screwdriver and a sledgehammer!

But in fact, if you want the bearing seats and the hub as a whole to serve you happily ever after, then remember:

1) Monitor the chain tension

2) Monitor the condition of the bearings!

3) Timely replacement of bearings

4) Use of quality bearings

5) When replacing bearings, use a hair dryer AT A MINIMUM! And it's best that you have an anchor puller.

Seats often cannot be repaired, and then the question arises of replacing the part associated with the bearing and which has lost the nominal parameters of the seat. This type of repair is not economically feasible. The solution in this situation is repair using Dimet technology.

Let's look at examples of repairing seats using the cold gas-dynamic spraying method.

Motorcycle hub bearing seat.

The defect of the seat is that the outer ring of the bearing rotates during operation, which puts additional loads on the axis of the inner ring and on the bearing itself.

Image 1. Seat for the outer bearing race on a cross-country motorcycle wheel.

To eliminate this problem, it is necessary to add a layer of metal to the inner diameter of the hub. The hub is made of aluminum alloy. Before applying the composition, we pre-treat the surface with abrasive composition K-00-04-16. The application of an additional layer is carried out in the third mode of the Dimet-405 apparatus. Spraying is carried out with a reserve. The final processing of the coating is carried out at low cutter feed at high speeds.

Image 2. Stages of repair (a - aluminum layer applied with a reserve, b - finishing version of the finished seat)

Crankshaft half ring seat

The seat of the remote semi-ring of the crankshaft of the cast-iron Mercedes-Benz cylinder block was repaired using Dimet technology. The final processing was carried out with a special cutter.

Wheel bearing seat

Repair of the Ford cast iron hub seat was carried out by applying an aluminum layer 0.3 mm in size. These manipulations provided the necessary tension in the connection.

Image 1. Stages of repair (a – initial, b – final)

Electric motor bearing seat

Repair of bearing seats in the electric motor housing was carried out using an aluminum composition device, spraying mode - “3”. The images show the stages of repair.