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Common Problems of NSK Bearings

Inspection and acceptance

To check NSK bearings, the user must have the following knowledge:

(1) Which standard is the inspection of NSK bearing products;

(2) What are the inspection items of NSK bearing commodities, and why should these items be inspected;

(3) Before the quality inspection of NSK bearing products, what preparations need to be done and why these preparations should be done;

(4) Under what conditions, what methods, and what instruments are used for the inspection items of NSK bearing commodities, what test results must be within what tolerance range to be qualified;

(5) NSK bearing commodities are sometimes very large and cannot be inspected at 100%, so what kind of sampling plan should be adopted and how many samples should be taken for inspection in order to represent the quality of all commodity bearings more comprehensively and with sufficient reliability, and The results of the inspection are measured according to what criteria are used to determine whether the batch of goods is a qualified batch that should be accepted or an unqualified batch that should be rejected.

The acceptance inspection of NSK bearings can usually be divided into three categories, namely:

Routine inspection-a routine general inspection when NSK bearings arrive.

Routine inspection—Inspect items such as dimensional accuracy, rotation accuracy, bearing clearance and bearing residual magnetic strength related to assembly of NSK bearings.

Special inspection-check the vibration quality, noise quality and other special requirements of NSK bearings.

With the advent of internationalization, domestic bearing codes are gradually in line with imported bearing codes. The latest published national standards show that domestic code names are basically consistent with international ISO standards.
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Installation and disassembly

NSK bearing installation:

1. Before installing the imported bearing on the shaft, the fixed pin of the bearing jacket must be removed, and the surface of the journal should be polished smooth and clean, and the journal should be coated with oil to prevent rust and lubrication (allowing the bearing to rotate slightly on the shaft).

2. Apply lubricating oil to the mating surfaces of the bearing housing and bearing, and install the bearing into the bearing housing. Then put the assembled bearing together with the NSK bearing seat on the shaft. Push to the desired location to install.

3. Do not tighten the bolts that secure the bearing housing first, but allow the bearing housing to rotate in the bearing housing. Also install the other end bearing and seat on the same shaft, turn the shaft a few times, and let the bearing itself find the correct position automatically. Then tighten the bearing seat bolts.

4. Install an eccentric sleeve. First put the eccentric sleeve on the eccentric step of the bearing inner sleeve, and tighten it by hand along the rotation direction of the shaft. Then insert or hold the small iron rod into the countersink hole. Use a hammer to strike the iron rod in the direction of rotation of the shaft. Install the eccentric sleeve firmly, and finally tighten the hexagon socket screws on the eccentric sleeve.

NSK bearing disassembly:

1. Disassembly of the outer ring

To disassemble the interference fit outer ring, set several screws for the outer ring to squeeze the screw on the circumference of the housing in advance, and tighten the screw on one side while disassembling. These screw holes are usually covered with blind plugs, tapered roller NSK bearings, and other separate NSK bearings. Several cuts are provided on the housing shoulders, using pads, disassembling with a press, or gently tapping to remove.

2. Disassembly of cylindrical hole NSK bearing

The disassembly of the inner ring can be pulled out using a pressure machine. At this time, pay attention to the inner ring to withstand its pulling force. The hydraulic method is used to dismantle the inner ring of large NSK bearings. Oil pressure is applied through the oil hole provided on the shaft to make it easy to pull out. NSK bearings with large widths are used in combination with drawing tools for disassembly operations. Induction heating method can be used to dismantle the inner ring of NU and NJ cylindrical roller NSK bearings. The method of heating the local area in a short time to make the inner ring expand and pull.

3. Disassembly of tapered bore NSK bearings

Disassemble the relatively small NSK bearing with adapter sleeve, support the inner ring with a block fastened on the shaft, turn the nut back a few times, and use the block to beat with a hammer to remove. Large NSK bearings are easier to disassemble with hydraulic pressure. Oil is fed under pressure in the oil hole on the tapered shaft to expand the inner ring and remove the NSK bearing. During operation, the NSK bearing may suddenly come out. It is better to use the nut as a stopper.
Eric Bearing Limited has enough stock for NSK 6912DDU, please click here.
 

Lubrication maintenance

NSK bearing lubrication:

The oil bath of NSK bearing is smooth

Oil bath smoothing is a common smoothing method in NSK bearings, suitable for low and medium speed bearings. Part of the NSK bearing is immersed in the oil groove, the smooth oil is carried by the rotating bearing parts, and then flows back to the oil groove. The oil surface should be slightly lower than the center of the lowest rolling element.

NSK bearings have smooth oil dripping

The oil drip smooth is suitable for NSK bearing parts that need to be supplied with smooth oil quantitatively. The amount of oil drip is preferably one drop every 3-8 seconds. Excessive amount of oil will cause the bearing temperature to increase.

The circulating oil of NSK bearings is smooth

Use the oil pump to send the filtered oil to the NSK bearing components, and then use the smooth oil after the bearing to filter and cool. Because the circulating oil can take away certain heat and cool the bearing, this method is practical for bearing parts with higher speed.

NSK bearings have a smooth spray

The dry shrinkage air is mixed with smooth oil through the sprayer to cause oil mist. In the NSK bearing, the airflow can effectively cool the bearing and prevent the intrusion of impurities. This method is suitable for the smoothing of high-speed and low-temperature bearing components.

NSK bearings have a smooth radiation

Use the oil pump to shoot low-pressure oil into the NSK bearing through the nozzle, and the oil injected into the bearing flows into the oil groove through the other end of the bearing. When the bearing rotates at a high speed, the rolling elements and the retainer also cause the surrounding air to generate airflow at a relatively high rotation speed. It is difficult to send the smooth oil to the bearing in an individual smooth way. At this time, the smooth oil must be sprayed by low pressure radiation In the bearing, the position of the nozzle should be placed between the inner ring and the center of the maintenance frame.