Precision Bearings. For Machine Tool Applications. A Quick Reference Guide

Transcription

1 Precision Bearings For Machine Tool Applications A Quick Reference Guide

2 Super Precision Bearings Product Range Several types of super precision bearings are available from, including the ROBUST series of high performance bearings, the special series of bearings for unique and specialized applications, and the standard series bearings. High Precision Angular Contact Ball Bearings Ultra High-Speed Single Row Cylindrical Roller Bearings Standard Series Basic super precision bearings manufactured to conform to ISO standards. 7xx, 72xx, 79xx series Three types of contact angle: 15 (C), 25 (A5), 3 (A) Two types of cage design: Select either phenolic (TR) or polyamide (TYN), depending on application requirements Robust Series Standard Series High performance cylindrical bearings designed for ultra high speed applications, such as machining center spindles. Two types of cage material: Brass (MR) (1) and PEEK resin (TP) Three types of roller material: Steel, SHX and Ceramic Ultra high speed ROBUST RXH design can be used up to 3 million d m n. (1) MR cage is used in the standard series Ultra High-Speed Angular Contact Ball Bearings Double Row Cylindrical Roller Bearings Robust Series BNR, BER Series High performance bearings developed for high speed operation with low temperature rise. Suitable for ultra high precision machining applications, and ultra high speed applications. Two types of contact angle: (BNR), 25 (BER) Two types of ball material: steel (S type) and ceramic (H type) Two types of cage design: Select either phenolic (T) or polyamide (TYN), depending on application requirements ROBUST series also can be used for ultra high speed applications of over 3 million d m n. Standard Series High Rigidity Series Designed to deliver high rigidity in high speed applications such as lathe spindles. Two types of cage material: Brass (MB), PPS resin (TB) Standard specification E44: Outer ring oil holes and groove Robust Series BAR, BTR Series High-Speed Angular Contact Thrust Ball Bearings High rigidity thrust bearings for lathe applications. Two types of contact angle: 3 (BAR), 4 (BTR) Two types of ball material: steel (S type) and ceramic (H type) Special Series for Machine Tool Applications Angular Contact Thrust Ball Bearings for Ball Screw Support High rigidity thrust bearings designed specifically for ball screw support applications in machine tools. Contact angle: 6 Can be universally matched to any required rigidity specification or life cycle A pre-greased line using special grease is also available BGR Series Ultra High Precision Angular Contact Ball Bearings High Performance bearings developed specifically for internal grinding or high speed motor applications under spring preload. Bore size range: ø625 mm, contact angle: 15 Non separable type Universal combinations (DU and SU) Special Series for Injection Moulding Machines Angular Contact Thrust Ball Bearings for Ball Screw Support The high load capacity design delivers five times the life expectancy compared to ball screw support bearings for machine tool applications of a similar size. The number of rows can also be reduced. Easier handling than tapered roller bearings or thrust spherical roller bearings as a result of non-separable configuration Optimum ball bearing design results in lower rotational torque Can be universally matched to any required rigidity specification or life cycle Sealed Angular Contact Ball Bearings High Precision Deep Groove Ball Bearings Special Series Pre greased and sealed to reduce handling problems. Suitable for maintenance of machine tool spindles. Standard series super precision angular contact ball bearings ROBUST series high speed angular contact ball bearings Bore size range: ø31 mm in ISO series 1 and 19 (7xx and 79xx) Special Series Suitable for high speed and high precision motors. Three types of cage : Ball guided polyamide cage (T1X,TYA) and inner ring guided phenolic cage (T), selection depends on the application Suitable for silent or low vibration operation

3 Comparison of Lubricating Methods Lubricating Methods Advantages Disadvantages Grease Lubrication Oil Mist Lubrication Jet Lubrication Low cost Limitation of temperature rise is possible. Maintenance free Since new oil is always fed, no fear of oil deterioration. Dust and cutting fluid cannot easily enter. Since the oil flow rate is high, dust and cutting fluid cannot enter and seizure hardly ever occurs. Because of cooling by oil, the bearing temperature can be controlled to some degree. If packed grease deteriorates, seizure may occur. May allow penetration of dust or cutting fluid. Pollution of environment. Oil supply quantity varies depending on the oil viscosity and temperature, so control of a small flow rate is difficult. It is difficult to confirm that oil is actually fed. Frictional loss is high. Since oil leaks, it is difficult to use for vertical spindles. Cost is high. Oil-Air Lubrication Since oil quantity control is possible, the optimum quantity of oil is fed and heat generation is low. Besides little heat-generation, there is a cooling effect of the air, so the temperature is low. Since new oil is always fed, no fear of oil deterioration. Dust, cutting fluid cannot easily enter. Environmental pollution mist is slight. Grease Brand Names and Properties Brand Names Cost is rather high. Confirmation of whether oil is actually fed to bearing is difficult. The Recommendable Grease Quantities for High-speed Spindle Bearings Bore number Bore diameter (mm) Manufacturers Angular Contact Ball Bearings: 15% of internal free space BNR19, BGR19 79XX Thickeners BGR1 7XX BGR2 72XX Base oils BNR1, BAR1 BTR Base oils viscosity mm (4 C) NN Dropping point ( C) Cylindrical Roller Bearings: 1% of internal free space Working temperature range ( C) NN NN3 * Do not operate bearings at full spindle speed when bearings are first installed. It is necessary to break the grease in. Contact for assistance Main application N Unit: cc/row MTE Barium complex Ester oil 2 2-3~+12 Bearings for high speed spindles, high speed cylindrical roller bearings. MTS Urea Ester + Synthetic hydro carbon oil ~+13 Bearings for high speed spindles. Isoflex NBU15 Klüber Barium complex Diester oil + Mineral oil ~+12 Bearings for main spindles. Isoflex NCA15 Klüber Special Ca Ester oil 23-4~+13 Bearings for main spindles. Mobilux 2 Mobil Lithium Mineral oil ~+11 Bearings for boring heads, live centers. Multemp LRL3 Kyodo Yushi Lithium Tetraester oil ~+13 Bearings for main spindles. Stabragus NBU8EP Klüber Barium complex Mineral oil ~+13 Heavy load cylindrical roller bearings. Alvania 2 Shell Lithium Mineral oil ~+11 Ball screw support bearings. ENS Diurea Tetraester oil ~+16 Bearings for motors.

4 High-Precision Single-Row Angular Contact Ball Bearings Conventional Type 72, 7, 79 Series 7 16 A5 TR V1V DU L P4Y 8 BNR 1 S T V1V P4 : ISO Class 4 (ABEC7) P4Y* : ISO Class 4 P3 : Dimensions - ISO Class 4 Running Accuracy : ISO Class 2 P2 : ISO Class 2 (ABEC9) *P4Y indicates special ID/OD tighter tolerancing for ease of matching sets. 1 Preload: L - Light M - Medium H - Heavy Gxx - Preload in Kfg (G5=5 Kgf) CPxx - Median Preload in Microns (CP1=1µm) CAxx - Median Axial Clearance in Microns (CA15=15 µm) Mounting Configuration: SU - Single Universal DU - Duplex Universal DB, DF, DT - Duplex Arrangement DBD, DFD, DTD, DUD - Triplex Arrangement DBB, DFF, DBT, DFT, DTT, QU - Quad Arrangement Seal: No Symbol - Open type V1V - Non contact rubber seal Retainer: T - Phenolic Cage TYN - Polyamide Cage Material: Blank Symbol : Bearing Steel (SUJ2) SN24 : Ceramic Balls Contact Angle: A = 3 A5 = 25 C = 15 Bore Diameter Designator: Bearing Series: ROBUST, High-Speed Type BNR 1, BNR 19 Series DU L P4Y P4 : ISO Class 4 (ABEC7) P4Y* : ISO Class 4 P3 : Dimensions - ISO Class 4 Running Accuracy : ISO Class 2 P2 : ISO Class 2 (ABEC9) *P4Y indicates special ID/OD tighter tolerancing for ease of matching sets. 1 Preload: EL - Extra Light L - Light Gxx - Preload in Kgf (G5=5 Kgf) CPxx - Median Preload in Microns (CP1=1µm) CAxx - Median Axial Clearance in Microns (CA15=15µm) Mounting Configuration: SU - Single Universal DU - Duplex Universal DB, DF, DT - Duplex Arrangement DBD, DFD, DTD, DUD - Triplex Arrangement DBB, DFF, DBT, DFT, DTT, QU - Quad Arrangement Seal: No Symbol - Open type V1V - Non contact rubber seal Retainer: T - Phenolic Cage TYN - Polyamide Cage T42 - PEEK Cage Material: S - Steel Ball H - Ceramic Ball Dimension Series: 1 : Same bore diameter, outside diameter, and width as the 7 series 19 : Same bore diameter, outside diameter, and width as the 79 series Bearing Type: BNR - Contact Angle BER - 25 Contact Angle BGR - 15 Contact Angle Nominal Bore Diameter: 1. See far right for more extensive definition of Precision Class (P4Y) ISO Class 4 or AFBMA ABEC7 Standard Ultra-High Fafnir Barden NDH MRC SKF FAG RHP Type 1 Speed Type 1 721CTY*P4 721A5TY*P4 71CTY*P4 71A5TY*P4 791CTY*P4 791A5TY*P4 5BNR1T*P4 5BNR19T*P4 2MM21WI* 3MM21WI* 2MM911WI* 3MM911WI* 2MM931WCR* 21H* 221H* 11H* 211H* Q221*7 QH221*7 QL21*7 QHL1*7 21R*7B 721*7B 11KR*7B 711R*7B 191R*7B 721CP4* 721ACP4* 71CP4* 71ACP4* 7191CP4* 7191ACP4* B721CTPAP4* B721CETPAP4* B71CTPAP4* B71ETPAP4* B7191CTPAP4* B7191ETPAP4* 1 721CTP4* 721ETP4* 71CTP4* 71ETP4* 791CTP4* 791ETP4* 1. Phenolic cage = T, Polyamide cage = TY Notes: Underlined digits (1) vary with bearing bore. Asterisks indicate the position of the preload designation for Universal Duplex Bearings. Preload Designation for Universal Duplex Bearings Preload Fafnir Barden NDH MRC SKF FAG RHP Light DUL DUL DL DTL DUL DGA UL DUL Medium DUM DUM DM DTX DUM DGB UM DUM Heavy DUH DUH DH DTT DUH DGC US DUH

5 Thrust Angular Contact Ball Bearings 1 BAR 1 S TYN DB L P4A 1 TAC 2X PN7 +L C6 P4A : ISO Class 4, O.D. is Special P2A : ISO Class 2, O.D. is Special Preload: L : Standard Preload EL : Standard Preload for High Speed Applications CP : Special Preload CA : Special Axial Clearance Combination: DB : Back to Back Duplex Retainer: TYN : Polyamide Cage Material: S : Steel Ball H : Ceramic Ball Dimension Series: 1X : Arranged with NN3XX Series Bearing Type: BAR Contact Angle BTR - 4 Contact Angle Bearing Bore Diameter (mm): Preload Class: C6 : Standard Preload for Grease Lubrication C7 : Standard Preload for Oil Lubrication Spacer (Inner Ring): PN7 : ISO Class 4, O.D. is Special Dimension Series: 2X 29X Bearing Type: - High Speed Type w/revised Internal Features - High Speed Type w/revised Internal Features Bearing Bore Diameter (mm): Ball Screw Support Bearings 3 TAC 62 B DF C1 PN7A PN7A - Standard Accuracy (Equivalent to ISO Class 4) PN7B - Special Accuracy (Bore diameter and OD are exclusive to. Equivalent to ISO Class 4. For SU arrangement only. Preload: C1 - Metric Series C11 - Inch Series Mounting Configuration: SU - Single Universal DU - Duplex Universal DB, DF, DT - Duplex Arrangement DBD, DFD, DTD, DUD - Triplex Arrangement DBB, DFF, DBT, DFT, DTT, QU - Quad Arrangement Internal Design: B - High Capacity & Higher Speed (Replaces A type) Bearing O.D.* (mm): Cylindrical Roller Bearings NN 3 17 TB KR E44 CC P4 P2 - ISO Class 2 P4 - ISO Class 4 Radial Clearance: CC1 - Standard clearance for cylindrical bore CC - Standard clearance for tapered bore CCG - Special radial clearance Lubrication: E44 - Outer ring with machined lubrication groove and holes (Double Row Only) Bore Configuration: KR - Ultra Precision Tapered Bore (1:12) Blank symbol - cylindrical bore Retainer: MB - Roller guided machined brass cage (Double Row) TB - Roller guided phenolic resin TP - Outer ring guided PEEK resin cage MR - Roller guided machined brass cage (Single Row) Designation: RS - Bearing Steel (SUJ2) (rings and rolling elements) (Single Row) RX - Heat Resistant Steel (SHX) (rings and rolling elements) (Single Row) RXH - Heat Resistant Steel (SHX) for rings and ceramic rolling elements (Single Row) No symbol : SUJ2 steel Bore Diameter Designator: Bearing Type: Diameter Series: Width Series: Bearing Bore* (mm): *For inch series bearings, the fractional portion of the size is omitted. Cylindrical Roller Designator: NN - Double Row, Inner Ring Guided Rollers N - Single Row, Inner Ring Guided Rollers

6 Fitting of Shaft and Housing It is of utmost importance that shafts and housings are accurately and precisely mated in order to take full advantage of the precision bearings capabilities, which include rotational accuracy, high speed performance, and low heat generation. When the inner ring or outer ring is mounted onto a shaft or into a housing with some interference, the shape of shaft or housing (out of roundness) is transferred to the bearing raceway surfaces and affects running accuracy. When different arrangements of angular contact ball bearings are used, cylindricality affects the distribution of preload for each bearing. Therefore, the mating parts should be as accurate as possible. Inaccurate mating of parts can cause the formation of peaks or ridges along the shaft of a precision lathe, which can affect the quality of finished work. Bearing Type 3 Shaft Outer Diameter (mm) over incl. FITS 1 ON SHAFTS Tolerance of Shaft 2 Outer Diameter (mm) minimum maximum Target Interference 2,4 (mm) minimum maximum Machine tool spindle bearing T.25 T.3 T.4 T.4 T.5 T Angular contact thrust ball bearing for ball screw support Bearing Type 3 Angular Contact Ball Bearing (Fixed side) Angular Contact Ball Bearing (Free side) Cylindrical Roller Bearing Angular Contact Thrust Ball Bearing for Ball Screw Support Housing Bore Diameter (mm) over incl FITS 1 ON HOUSING Tolerance of Housing 2 Bore Diameter (mm) minimum maximum Target Clearance 2,4 (mm) minimum maximum.2 L.2 L.3 L.3 L.5 L.6 L.6 L.9 L.9 L.15 L.2 L.2 L.2 L.2 L.2 L 1. The fitting data above provides general recommendations for machine tool spindles operating under normal conditions and for d m n values of less than 8,. For high speeds, heavy loads, or outer ring rotation, please contact for assistance. 2. Use the target interference when the bearings can be matched to the shaft or housing. Otherwise use the shaft outer diameter and housing bore min and max for random matching. 3. Applies to angular contact ball bearings: 7XX, 79XX, 72XX, BNR and BER Angular contact thrust ball bearings: BAR, BTR and TAC Cylindrical roller bearings: N1XX, NN3XX, NN39XX, NN49XX and NNU49XX 4. T=Interference or tight fit L=Clearance or loose fit.6 L.6 L.8 L.8 L.1 L.11 L.11 L.15 L.15 L.22 L.2 T.2 T.2 T.2 T.2 T

7 f: Offset of front face b: Offset of back face Fig. 1 Offset of Inner & Outer Rings Universal Combination Bearings offers universal bearings, SU or DU, that can be used to create various angular contact ball bearing arrangements. A universal angular contact ball bearing is one with the same offset ground on both front and back faces. Reference Fig. 1, (f=b). This offset relates directly to the bearing s stringent preload control and enables universal bearings to be combined or form back to back (DB, DBD, DBB) or face to face (DF, DFD, DFF) sets. Precision Class (P4Y) also provides universal bearings with tighter bore and outer diameter tolerance control designated by precision class P4Y. This aspect makes universal bearings suitable for random matching to form combinations, yet maintain equal load sharing and high running accuracy for sets. Tolerance of P4 and P4Y Accuracy Variation of outer diameter tolerance Super Precision Universal Duplexed Angular Contact Bearings Features State-of-the art preload control Easier matching with tighter Bore & OD tolerances - P4Y High Point of Eccentricity marked on inner and outer rings Packaged marked with actual bore, OD, and width deviation from nominal (units are microns µm) High performance phenolic cage Variation of bore tolerance When bearings are mounted in random matching method, variation of tolerance should be considered. Universal Bearing Combinations Bore and Outer Diameter Tolerance Bore Diameter Over Incl. Tolerance of Bore Diameter of Inner Ring High P4 Low Unit: µm P4Y (Controlled to median value) High Low DB DF DT DBD DFD DTD * Tolerances for bearings under 3mm bore are the same as values quoted between 3-5 mm bore. Outer Diameter Over Incl. Tolerance of Outer Diameter of Outer Ring High P4 Low Unit: µm P4Y (Controlled to mediam value) High Low DBB DFF DBT Under DFT DTT Tolerances for bearings under 5mm outer diameter are the same as values quoted between 5-8mm outer diameter.

8 Cause and Countermeasures for Operating Irregularities Irregularities Possible cause Countermeasures Abnormal load Improve the fit, internal clearance, preload, position of housing shoulder, etc. Loud metallic sound 1 Incorrect mounting Insufficient or improper lubricant Improve the machining accuracy and alignment of shaft and housing, accuracy of mounting method. Replenish the lubricant or select another lubricant. Contact of rotating parts Modify the labyrinth seal, etc. Noise Loud regular sound Dents generated by foreign matters, corrosion, flaws, or scratches on raceways Brinelling Replace or clean the bearing, improve the seals, and use clean lubricant. Replace the bearing, and use care when handling bearings. Flaking on raceway Replace the bearing. Irregular sound Excessive clearance Penetration of foreign particles Flaws or flaking on balls Improve the fit, clearance, and preload. Replace or clean the bearing, improve the seals, and use clean lubricant. Replace the bearing. Excessive amount of lubricant Reduce amount of lubricant, or select stiffer grease. Insufficient or improper lubricant Replenish lubricant or select a better one. Abnormal temperature rise Vibration (Radial runout of shaft) Leakage or discoloration of lubricant Abnormal load Incorrect mounting Creep on fitted surface, excessive seal friction Brinelling Flaking Incorrect mounting Penetration of foreign particles Too much lubricant. Penetration by foreign matter or abrasion chips Improve the fit, internal clearance, preload, or position of housing shoulder. Improve the machining accuracy and alignment of the shaft and housing, accuracy of mounting, or mounting method. Correct the seals, replace the bearing, or correct the fitting or mounting. Replace the bearing and use care when handling bearing. Replace the bearing. Correct the squareness between the shaft and housing shoulder or side of spacer. Replace or clean the bearing, improve the seals. Reduce the amount of lubricant, select a stiffer grease. Replace the bearing or lubricant. Clean the housing and adjacent parts. Note 1 Squeaking may arise from grease lubricated ball bearings or cylindrical roller bearings (medium to large sized). This is especially true during winter when temperature will not rise, leaving fatigue or grease life unaffected. Consequently, such a bearing can continue to be used. If you have concerns regarding squeaking noise, please contact. Corporation Canada, Inc. Brazil 42 Goss Rd. P.O. Box McAdam Road Ann Arbor, Michigan Mississauga, Ontario L4Z 1N4 Canada Rua Treze de Mail (734) (95) andar-bela Vista Fax: (734) Fax: (95) Sao Paulo-SP Brazil, Latin America Mexico Fax: NW 17 Avenue, Suite 3 Minas Palacio No Col. San Antonio Zomeyucan Naucal de Jaurez Fax: C.P Estado de Mexico, Mexico Fax: MTB-499 Americas 23