Page 178 - needle bearings

Inner Rings
NTN

Inner Rings

Inner Rings Dimensional accuracy for inner ring
Many of the needle roller bearings use a shaft as the The dimensional accuracy (bore diameter "d", width "B"
direct raceway surface without using inner ring. However, and chamfer dimension "rs min"), profile accuracy and
it is recommended to use any of the inner rings described running accuracy of the inner rings are as shown in
hereunder, together with needle roller bearing, where Tables 4.3 and 4.5 of Section 4 "Bearing accuracy"
applicable shaft can not be surface-hardened and (page A-26). And the standard accuracy class of these
surface-finished by grinding. Any inner rings are made of items conforms to JIS Class-0, but other inner rings
high carbon chrome bearing steel and finished by conforming to JIS Class-5 and -4 are also offerable on
grinding after heat-treated. request.
It is desirable to use an inner ring of wide width, where For the dimensional tolerance for raceway diameter (F)
the axial displacement of a shaft is great and also a seal shown in applicable Dimension Table, the inner ring is
is used at the outer side of bearing. finished so the radial clearance comes to ordinary
clearance (refer to Table 5.1 of 5.2 "Running clearance"
(page A-30) when it is combined with needle rollers.
Types and Designs Feel free to contact NTN for use of an inner ring
NTN inner rings are available in both of IR type with subjected to radial clearance other than ordinary
boundary dimensions of metric system and MI type with clearance.
boundary dimensions of inch system. The both ends of
inner ring raceway are chamfered in taper form to
facilitate fitting of the inner ring. On the other hand, any
inner rings with an asterisk ˞-mark are fine-chamfered
so as to allow greater axial displacement. In addition to
these inner rings, manufacture of special inner ring type
(with tail code: D) with oil hole on its center is also
available.
Particularly where high running accuracy is required, on
occasion the raceway surface of inner ring is finished by
grinding after fitted on a shaft. In such a case, an inner
ring with grinding allowance for its raceway can be
supplied. Feel free to contact NTN for the detail of such
an inner ring.

Composition of nominal number
Nominal number comprises type code (IR or MI),
dimension code [bore dia. (d)ʷraceway dia. (F)ʷwidth
(B)] and tail code.
The dimension of inch series MI type is expressed at
the unit of 1/16 inch.

IR 20ʷ25ʷ18 D

Tail code
Dimension code

Type code

Fig. 1

B-116