21 NTN Main Spindle Bearings
Main Spindle Bearings 1. Cylindrical Roller Bearings CONTENTS 1. Cylindrical roller bearing 2 q Double-row cylindrical roller bearing 21 w Single-row cylindrical roller bearing 21 e Bearing number 21 r Accuracies of tapered of cylindrical roller bearing 21 t Accuracies of cylindrical roller bearings 21 y Radial internal clearance of cylindrical roller bearing 22 u Recommended fit of high-precision cylindrical roller bearing 222 i Recommended lubrication specifications 22 o High-speed cylindrical roller bearings N1HSR type 22! Eco-conscious air-oil lubricated cylindrical roller bearings N1HSL type 22!1 Dimension tables for cylindrical roller bearings Double-row cylindrical roller bearings22 Single-row cylindrical roller bearings 2 High-speed cylindrical roller bearings2 Eco-conscious high-speed cylindrical roller bearings 2!2 Taper gage and internal clearance adjustment gage for NTN precision cylindrical roller bearings 22! Dimension tables for taper gage 2! Dimension table for residual internal clearance adjustment gage 2 21
1. Cylindrical Roller Bearings On a cylindrical roller bearing, the rollers and raceways are in linear contact. This type of bearing can bear a larger radial load. Also, its structure is adopted for high-speed operation. A cylindrical roller bearing used for the main spindle of a machine tool can have either a double- or singlerow configuration, and certain variants have a tapered so the radial internal clearance can be adjusted. 1 Double-row cylindrical roller bearing Double-row cylindrical roller bearings are available in two types, NN and NNU, and two series, and. The rollers in the NN type bearing are guided by the ribs of the inner ring. The rollers in the NNU type bearing are guided by the ribs of the outer ring. Two types of bearing, cylindrical type and tapered type (which allows adjustment of radial internal clearance of bearing) are available. The bearings come in two types, standard type and high-speed HS type. Brass machined cages, adopted as standard, are applicable to both of grease lubrication and air-oil lubrication. 2 Single-row cylindrical roller bearing Single-row cylindrical roller bearings are available in two types, standard N1HS type and high-speed N1HSR type. The N1HS type bearings have highstrength brass casting machined cages, while the N1HSR type bearings have special resin molding cages, which can be used for both of grease lubrication and air-oil lubrication. The N1HSL type bearing, being eco-friendly type and applicable to air-oil lubrication only, is a variation from the high-speed N1HSR type bearing. Cylindrical N1HS type Tapered Cylindrical N1HSR type Tapered Cylindrical NNU type Tapered Cylindrical N1HSL type Tapered Fig. 1.2 Cylindrical NN type Fig. 1.1 Tapered 21
Bearing number NN,, NNU type NN 2 HS K CNA P AccuracycodePJIS class P2JIS class2 PJIS class UPSpecialhighprecision Internal clearance codesee Table 1.1. ExternalconfigurationcodeKTaperedinnerringtaperratio1/ No codecylindrical inner ring InternalmodificationcodeNocodeStandardspecification HSHighspeedspecification Nominal diameter Dimension series code Bearing type codenndouble row/ with ribbed inner ring NNUDouble row/ with ribbed outer ring N1 type N 1 2 HSR T K CNA P Cage code TPEEKresinmoldcage ApplyoHSRtype No codehigh strength machined brass cage Internalmodificationcode HSStandardspecification HSRHighspeedspecification Bearingtypecode NSingle row/with ribbed inner ring N1HSL type N 1 2 HSL T K CNA P +TKZ Spacer code Eco- friendly nozzle Cage code TPEEK resin mold cage Internalmodificationcode notesn1hslbearing series code TKZ Eco-friendlynozzleorSpacerwithEco- friendly nozzleincaseofn1hsltype Accuracies of tapered of cylindrical roller bearing NTN specifies the accuracies of tapered conforming with JIS Classes and 2 as shown below. Poor accuracies of the tapered lead to tilt of the inner ring, causing poor performance of bearings, as well as premature seizure and flaking. For higher accuracies with the main spindle, use of a taper gauge is recommended. As for the target of taper angle and adjustment of taper-to-taper contact, refer to. Handling of Bearings, - Cylindrical roller bearing tapered and main spindle taper angle in the Technical Data section. Table 1.1 Allowance and tolerance of taper-d bearings Unit: d dmp d1mp dmp (approx.) Vdp Class Class 2 Class Class 2 Class Class 2 over incl. high low high low high low high low 1 1 2 1 1 2 1 1 1 2 2 2 2 Note: NTN standard values 1 1 1 1. 2. 2. 1 1. 1. 2 2... d B d1 Theoretical tapered d dmp B d1mp dmp d1 d1mp Tapered having single plane mean diameter deviation Tolerance of 1/ taper angle 1. 2 2 2. 1 d1d B VdpSingle radial plane diameter variation dmpsingle plane mean diameter deviation (at theoretical small end on tapered ) d1mpsingle plane mean diameter deviation (at theoretical large end on tapered ) BNominal inner ring width Fig. 1. 21
Accuracies of cylindrical roller bearings Table 1.2 Inner rings Nominal diameter d Single plane mean diameter deviation dmp Class Class 1 Class 1 1 over incl. high low high low high low 1 1 1 2 1 1 1 2 1 1 1 1 2 1 1 2. 2. Single radial plane diameter variation Vdp Diameter series Diameter series Class Class Class 2 1 1 1 2 1 1 2. 2. Class Class Class 2 1 1 1 1 2. 2. Mean diameter deviation Vdmp Class Class Class 2 2.. 1. 1. 2 2... Inner ring radial runout Kia Class Class Class 2 1 The tolerance of diameter deviation ds applicable to classes and 2 is the same as the tolerance of single plane mean diameter deviation dmp. 1 1 2. 2. 2. 2. 2. Table 1. Outer rings Nominal diameter D 1 1 2 1 1 1 2 1 Single plane mean outside diameter deviation Dmp Diameter series Class Class 1 Class 1 1 over incl. high low high low high low 1 1 1 2 2 2 1 1 1 Single radial plane outside diameter variation VDp Diameter series Class Class Class 2 Class Class Class 2 1 1 1 2 2 2 1 1 1 1 1 1 1 21 2 1 1 Mean single plane outside diameter variation 1 1 1 VDmp Class Class Class 2. 2 2 2. 2.. Outer ring radial runout Kea Class Class Class 2 1 1 1 2 2 2 1 2. 2 The tolerance of outside diameter deviation Ds applicable to classes and 2 is the same as the tolerance of mean single plane outside diameter deviation Dmp. 21
Face runout with Sd Width deviation Bs Single bearing Class Class Class 2 Class Class Class 2 high low high low Unit: Width variation VBs Class Class Class 2 1. 2. 1. 1. 1. 2. 1 2 1 2 1. 1. 2. 1 1 2. 2 2 2 1 2. 1 1 Outside surface inclination SD Class Class Class 2 Width deviation Cs All classes Unit: Width variation VCs Class Class Class 2 1 1 1. 1. 2. 2. 2. Identical to Bs relative to d on the same bearing. 2. 1. 1. 2. 2. 2. 1 1 1 1 2 1 1 2 21
Radial internal clearance of cylindrical roller bearing Non-interchangeable radial internal clearance of cylindrical roller bearing Two types of radial internal clearance of a cylindrical roller bearing are available; non-interchangeable radial internal clearance with which the combination of outer ring and inner ring cannot be changed and interchangeable radial internal clearance that allows alteration of the combination of outer ring and inner ring. The clearances are common to both the doublerow cylindrical roller bearings and the single-row cylindrical roller bearings. For machine components including the main spindle of a machine tool that requires high precision, bearings with noninterchangeable radial internal clearance of which clearance range is small are used. If a tapered bearing is used and its after assembled internal clearance should be close to zero, adoption of clearance in the range between CNA and CINA is recommended for double-row cylindrical roller bearings. As for the cylindrical bearings, bearings with noninterchangeable radial internal clearance of which after assembled internal clearance is further small are available. For details, contact NTN Engineering. Table 1. Cylindrical bearings Unit: Nominal diameter d Cylindrical bearing 1 over incl. min min min 2 1 1 1 1 2 22 2 2 1 1 1 1 1 2 22 2 2 1 1 1 1 1 1 1 2 2 2 2 1 1 1 2 2 2 1 1 1 2 2 2 2 2 1 1 1 1 1 The code for normal internal clearance is NA. Ex: N1HSNA 2 2 1 1 1 1 1 1 1 1 2 22 2 2 Table 1. Tapered bearings Nominal diameter d 2 2 Tapered bearing 2 over incl. min min min min Unit: 1 min 2 1 1 1 1 2 22 2 2 1 1 1 1 1 2 22 2 2 1 1 1 1 1 1 1 2 2 2 2 1 1 1 2 2 2 1 1 1 1 1 2 2 2 2 2 2 2 1 1 1 1 2 2 2 2 2 1 1 1 1 2 2 1 1 1 1 1 1 1 1 2 22 2 2 1 1 1 1 1 2 22 2 2 1 1 1 1 1 2 21 2 2 2 1 22 1 The code for normal internal clearance is "NA". Ex: N1HSKNA 2 Internal clearances CNA, CNA and C1NA apply to bearings of JIS class or higher.
Interchangeable radial internal clearance on cylindrical roller bearings (cylindrical ) Table 1. Unit: Nominal diameter d (Normal) over incl. min min min 2 1 1 1 1 2 22 2 2 1 1 1 1 1 2 22 2 2 1 1 1 1 1 1 2 2 1 2 1 1 1 21 22 2 2 1 1 1 21 22 1 1 1 1 1 2 22 2 1 1 1 1 1 1 2 22 2 1 1 1 1 1 1 22 2 2 2 1 Adjustment of clearance in tapered bearing After assembled internal clearance of a tapered bearing can be adjusted by controlling the drive-up of the tapered onto the shaft. Two types of adjusting methods area availablerepeated adjustment of width of spacer in a bearing and adjustment with using a remaining internal clearance gauge. The clearance gauge is convenient for mass-production. Refer to the section. Handling of Bearings, - Clearance adjustment for cylindrical roller bearing, "Method with remaining internal clearance gage " in the Technical Data section. 221
Recommended fit of high-precision cylindrical roller bearing In order to maintain high precision of a precision bearing, any of fits listed in Tables 1. and 1. is recommended under the following conditions: dmn value 1 (dmn: pitch circle diameter across rolling elements [mm] multiplied by speed [min -1 ]). When the dmnvalue is smaller than 1 (dmn value 1 ), ask NTN Engineering about the recommended fit, since e centrifugal force-derived expansion must be taken into consideration for the fit of shaft. Table 1. Fit to shaft Unit: Table 1. Fit to housing Unit: Nominal diameter d over incl. Fit between inner ring and shaft Nominal diameter D over incl. Fit between outer ring and housing 1 T T T T T T 1 1 2 T T 1T 1 1 1 1 2 T T T 2 1 1 Note 1: Target the median value. T: Interference fit Not applicable to tapered bearings T 1T 2 1 Note 1: Target the median value. T: Interference fit 1 T T T Fit of tapered bearing When fitting a tapered bearing onto a shaft, carefully and thoroughly adjust the fit of the tapered to the shaft to maintain high precision of the bearing. For details of adjustment of the taper angle, refer to. Handling of Bearings, Cylindrical roller bearing tapered and main spindle taper angle in the Technical Data section. 222
Recommended lubrication specifications Cylindrical roller bearings are usually used together with grease lubrication or air-oil lubrication. Recommended lubrication specifications are described below. Grease lubrication Recommended brand of grease Refer to. Lubrication of Bearings, -1 Grease lubrication in the Technical Data section. Recommended grease filling amount 1% of the capacities shown in the dimensions tables Recommended grease packing method Refer to. Handling of Bearings, -1 Cleaning of bearings and filling with grease in the Technical Data section. Air-oil lubrication Recommended location of nozzle Refer to. Lubrication of Bearings, -2 Air-oil lubrication in the Technical Data section. Recommended specifications of nozzle Nozzle dia.: From 1 to 1. mm Number of nozzles: One nozzle for each bearing, depth of nozzle should be four to six times of diameter of the. Recommended specifications of air-oil Oil type: Spindle oil Viscosity grade: ISO VG from 1 to 2 (2 is preferable) Table. 1. Air and oil amount NN Bearing models NNHS N1HS N1HSR Eco-friendly type N1HSL dmn value (1 ) Over Incl. 1 1 1 1 2 2 Oil amount per shot cm.2 Lubrication ntervals min 1 Oil consumption cm /h.1.2.2. Recommended air consumption NR/min 2 NR/min (Normal liter/minute)... NR means the volume of air at C and 1 atmosphere. 22