Needle Roller Bearings and Related Combined Bearings

Needle roller bearings are assembled with many slender needle rollers whose length is 3 times to 10 times the diameter. The structure is compact. The diameter of the inscribed circle of the needle rollers is relatively close to the outer diameter of the bearing, so it has a large radial load capacity.

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Needle Roller Bearings and Related Combined Bearings

Detail

1. Main structure type

1. Solid outer ring needle roller bearings NA 0000 and NKI
This type of bearing has an inner ring and an outer ring (with lock ring, needle roller and cage), and has a high limit speed. It is divided into single row and double row.
Single column: NA48, NA49, NA69 series (d<32mm) and NKI type.
The bearing outer ring with d≤7mm has double lock rings, and the bearing outer ring with d>7mm has double ribs.
Double column: NA69 series with d≥32mm.

2. Needle roller and cage assembly K 000000 type
The needle roller and cage assembly is an independent bearing unit, and the needle roller is precisely guided by the cage. This kind of bearing has no rings, small radial surface and large load-bearing capacity, and is suitable for supporting structures with limited radial installation dimensions. The surface of the shaft diameter and the surface of the shell hole matched with the bearing are directly used as the inner and outer rolling surfaces of the bearing. The surface hardness is generally 58-64HRC, the depth of the surface hardened layer is 0.6-1mm, and the Ra value of the surface roughness of the raceway is usually 0.32μm ; When the rotation accuracy of the shaft is required, the Ra value is 0.20μm. When the dimensional tolerance of the housing hole is G6, the dimensional tolerance of the shaft is recommended in Table 1. Shaft and housing bore raceway form tolerances are recommended in Table 2.

Table 1 Shaft Dimensional Tolerances

Nominal size of shaft diameter mm		Radial clearance
Exceed	Arrive	less than 0 set	0 set	Greater than 0 set
3	80	j5	h5	g6
80	200	h5	g5	f6

Table 2 Raceway shape tolerance

Raceway diameter mm	Exceed	3	10	18	30	50	80	120	180	250	315
Raceway diameter mm	Arrive	10	18	30	50	80	120	180	250	315	400
Cylindricity μm		2.5	3.0	4.0	4.0	5.0	6.0	8.0	10.0	12.0	13.0

3. HK type and BK type drawn outer ring needle roller bearings without inner ring and cage
Type HK: Both ends of the bearing are perforated.
BK type: One end of the bearing is a sealed type, which is used in the support of the journal without extending end, and can bear small axial movement force, and the end face is sealed to act as a seal.
This type of bearing consists of a thin-walled drawn outer ring, a cage and needle rollers. It has low cost and large load capacity, and is suitable for the support structure with limited radial installation size. The journal surface matched with the bearing is directly used as the raceway after hardening treatment. The bearing is installed into the seat hole with an interference fit, and it is not necessary to locate it axially. Bearings should be injected with a sufficient amount of grease before installation. Usually, there is no need to re-lubricate after assembly.

2. Cage material

Needle roller bearing cages are generally made of low-carbon high-quality steel, and other materials such as nylon can also be used.

3. Allowable inclination angle

Needle bearings generally do not allow angular inclination. During use, the maximum deflection angle on the full length of the needle roller shall not exceed 0.25% to 0.3%.

4. Tolerance and Clearance

The tolerance of needle roller bearings is generally only grade 0.

For needle roller bearings with inner and outer rings and cages (except for drawn outer rings and heavy series bearings), use the radial clearance value of cylindrical roller bearings. For heavy-duty series bearings with inner and outer rings and needle roller bearings with cages whose inner ring is delivered as a separate part, the radial clearance is checked according to the diameter of the raceway of the inner ring or the diameter of the inscribed circle of the needle roller assembly. Cylindrical rollers are used. The radial clearance value of the bearing.

Solid Outer Ring Needle Roller Bearings