Patent Publication Number: US-3879897-A

Title: Method and apparatus for producing the bearing races

Description:
United States Patent 1191 Kato &#39; 1 1 Apr. 29, 1975 METHOD AND APPARATUS FOR PRODUCING THE BEARING RACES [75] Inventor:  
  22 Filed: Dec. 8, 1972 21 Appl.No.:3l3,477  
 Hirosi Kato, lchikawa, Japan 51/50 PC1215 R, 215 C1, 215 H, 290, 291 327; 82/47, 102; 279/1 DC; 29/148.4 R, 417  
 [56] References Cited UNITED STATES PATENTS 1.229.162 6/1917 Starin 51/50 R X 2.429.517 10 1947 Knapp 51/50 PC 2.652.663 9/1953 Taylor 51/291 X 2,807,916 10/1957 Squire ct al 51/3 X 2.966.741 1/1961 Sullivan 29/417 X 3.019.563 2/1962 Martin 51/50 R 1634.978 1/1972 Uhtcnwoldt 51/3 X Primary Examiner-A1 Lawrence Smith Ass/slam Examiner-K. J. Ramsey Arromey, Agent, or Firm-Shapiro and Shapiro [57] ABSTRACT Bearing races are produced by grinding the inner and outer surfaces of an end portion of an elongated pipe of bearing steel to the shapes of the surfaces of a bearing race by inner and outer surface grinding wheels. and then severing the end portion from the pipe by a cutting edge provided by the outer surface grinding wheel. Another grinding wheel is provided for plane grinding the bearing race end surface which is formed by the cutting operation. Each of the grinding wheels may have rough and finish grinding parts for simultaneously finish and rough grinding said end portion and an adjacent portion, respectively. of the pipe.  
 17 Claims, 26 Drawing Figures PMENIEDAPRZSiSTS SHEET 030? 15 PMENTED APR 2 9 i975 saw on or 15 PMENTEUAPRZQiBTS SHEET DSOF 1S PATENTEBAPRZQIBYS SHEET [380$ 15 k h/l PATENTEDAFRZSIQYS 3.879.897  
 sum 10 0F 15 FIG.  
 FIG. I3 FIG.  
 Ff-JENTEEAFRZQAWS 3.879.897  
 SHEET 12 0F 15 FIG. 2|  
 PIXTENTEDAPRZSHYS SHEET 1 0F 15 30 FIG. 25  
 METHOD AND APPARATUS FOR PRODUCING THE BEARING RACES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for producing bearing races.  
 2. Description of the Prior Art Heretofore. bearing races have been manufactured either by treating pipe materials or bar materials of bearing steel in various steps. such as cutting. quenching. tempering. and grinding, or by treating the materials by various processes. such as plastic working. cutting. quenching, tempering. and grinding. In either case. it has been necessary to include a separate cutting operation. In preparing production facilities for bearings. the largest part of the investment in equipment is spent for cutting equipment. In addition. space and housing are required for accommodating the cutting equipment and a number of operators are required for operating the equipment. Furthermore, because the cutting operation includes the steps of loading and unloading the materials from the cutting equipment, the total manufacturing time is long. Also. extra personnel are required for loading and unloading the cutting machine.  
 SUMMARY OF THE INVENTION Accordingly. a principal object of the present invention is to provide a method and apparatus for manufac turing hearing races which reduces the heretofore high cost of equipment and personnel and shortens the manufacturing time.  
  In accordance with the invention. bearing races are formed from an elongated pipe of quenched and tempered bearing steel by a grinding machine which has formed-type grinding wheels for grinding the inner and outer surfaces of an end portion of the pipe to the shapes of the inner and outer surfaces of a bearing rate. One of the grinding wheels is provided with a cutting edge for severing the end portion from the pipe after grinding is completed to produce a bearing race from the end portion. thereby eliminating the need for separate cutting equipment. An additional grinding wheel is provided for plane grinding the bearing race end surface which is formed by the cutting operation. Each of the grinding wheels may have rough and finish grinding parts for simultaneously finish and rough grinding said end portion and an adjacent portion. respectively. of the pipe.  
 BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further described with reference to the accompanying drawings. which illustrate a preferred and exemplary embodiment. and wherein:  
  FIG. I is a plan view of apparatus in accordance with the invention. but with some of the covers removed to assist understanding. this view showing a pipe mounted in the apparatus;  
  FIG. 2 is a right side elevational view of the apparatus of FIG. I. but with an operating board omitted there from;  
  FIG. 3 is a transverse cross-sectional view taken approximately in the plane of line IIl-III of FIG. I;  
  FIG. 4 is a longitudinal cross-sectional view ofa pipe spindle employed in the apparatus of FIG. I, this view being taken approximately in the plane of line IVIV of FIG. I;  
  FIG. 5 is a longitudinal cross-sectional view of a grinding wheel and associated spindle employed in the apparatus of FIG. I for grinding the outer surface of an end portion of the pipe. this view being taken approximately in the plane of line VV of FIG. 1;  
  FIG. 6 is a partial longitudinal cross-sectional view taken approximately in the plane of line Vl-VI of FIG. I. this view showing a grinding wheel and associated spindle for grinding the inner surface of an end portion of the pipe&#34;.  
  FIG. 7 is a transverse cross-sectional view taken approximately in the plane of line VII-VII of FIG. 1;  
  FIG. 8 is a longitudinal cross-sectional view of a front bar feeder mechanism employed in the apparatus of FIG. I, this view being taken approximately in the plane of line VIII-VIII of FIG. 1;  
  FIG. 9 is a partial longitudinal cross-sectional view taken approximately in the plane of line IX-IX of FIG. 1, this view showing a grinding wheel and associated spindle for grinding the end surface of a bearing race;  
  FIG. 10 is a partial side elevational view showing the end of the pipe and the inner surface grinding wheel spindle broken away and in cross section to illustrate the inner surface grinding position of the apparatus of FIG. 1;  
  FIG. 11 is a partial transverse cross-sectional view taken through the end of the pipe for the inner surface grinding position of FIG. 10;  
  FIG. 12 is a partial transverse cross-sectional view taken approximately in the plane of line XII-XII of FIG. I0;  
  FIG. I3 is a side elevational view of a formed-type grinding wheel which may be employed in the system of FIG. 1 for grinding the outer surface of an end portion of the pipe;  
  FIG. 14 illustrates the operation of the grinding wheel of FIG. I3;  
  FIG. 15 is a side elevational view of another formedtype grinding wheel which may be employed in the apparatus of FIG. I for grinding the outer surface of an end portion of the pipe;  
  FIG. I6 illustrates the operation of the grinding wheel of FIG. 15;  
  FIG. 17 is a longitudinal cross-sectional view of a grinding wheel which may be employed in the apparatus of FIG. 1 for grinding the inner surface of an end portion of the pipe;  
  FIGS. 18-2] illustrate a method in accordance with the invention for manufacturing the outer race of a ball bearing;  
  FIGS. 22-25 illustrate a method in accordance with the invention for manufacturing the inner race of a ball bearing; and  
  FIG. 26 is a block diagram showing an electrical control circuit for operating the apparatus of FIG. 1 in a continuous manufacturing mode.  
 DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a grinding machine in accordance with the invention will be described with reference to the accompanying drawings. In FIG. 1. the grinding machine is provided with pipe spindle means A. grinding wheel spindle means B for outer surface grinding, grinding wheel means C for inner surface grinding, grinding wheel means D for plane grinding. front bar feeder means E, rear bar feeder means 75. and a power board 34. The spindle means A is secured to a bed 1 through a base 2. An elongated pipe 3 of quenched and tempered bearing steel to be worked is fed through an opening of said spindle and held and rotated by means of said spindle means A. This spindle means A has a construction as shown in FIG. 4 in which the spindle 4 is rotatably supported on a housing 5 by the front bearing means 6 and the rear bearing means 7, said housing 5 being secured to the bed 1 through said base 2. On the spindle, to a flange 8 located frontwards of the spindle 4 is secured a front power chuck 9, and on the rear end of the spindle 4 is secured a rear power chuck I0 to be rotated along with the spindle 4. Both front power chuck 9 and rear power chuck I0 are operated by oil pressure. The drawing shows the chucks in their open position. When the piston II is moved in the direction shown by the arrow, the conical inner surface of the piston 11 depresses the conical surfaces of pawls 12, which are mounted for radial movement in the chuck body 21, the movement of the pawls being limited by said chuck body 2I and a front cover 13, so that the steel pipe 3 (FIG. I) is gripped by the pawls when they are moved in radial directions. When the piston II is moved in the direction opposite to said arrow, pawls I2 are returned to their original positions by springs (not shown) for releasing the steel pipe 3. A shell portion I4 of the rear power chuck is provided in its outer surface with a V-channel for receiving a V- belt. The V-belt connects the V-pulley of a motor (not shown) and the shell I4 through a belt hole 15 in the housing 5 to rotate the spindle 4. Fitted in the middle portion between the front bearing means 6 and the rear bearing means 7 of the spindle 4 is a bushing 16, which is secured to the housing 5 by means of bolts (not shown) projected from said housing 5. The busing I6 is provided with two oil ports (not shown) and peripheral channels 17 and 18 each in communication with respective oil ports. one peripheral channel 17 being connected with an oil passage 19 in communication with a cylinder chamber on the side for opening the chuck, and the other peripheral channel I8 being connected with an oil passage 20 in communication with a cylinder chamber on the side for closing the chuck by moving the piston 11 in a direction shown by arrow. Said oil ports are connected to a change-over valve (not shown) and the chuck is opened and closed by operation of said change-over valve. A reference numeral 22 denotes a cover for the housing 5. With such a construction of the spindle means A, the operation of opening and closing the change-over valve instantaneously opens and closes the front and rear chucks 9 and 10 so that the steel pipe 3 may be supported and fed. The steel pipe 3 is firmly chucked at both the front and rear ends of the relatively long spindle I so that, if vibration occurs in the steel pipe itself, little vibration is produced in the middle portion between both chucks 9 and I0, and any vibration in the front working part of the front power chuck 9 caused by the vibration in the middle portion thereof is further reduced to promote working accuracy. thus providing a solid construction which can endure high speed rotation of lengthy steel pipe.  
  The grinding wheel spindle means B for outer surface grinding, as shown in FIG. 1 to FIG. 3, mainly comprises a grinding wheel spindle formed integrally with a slide base 24 which slides on the base 23 secured to the bed I, a driving motor 27 mounted on the slide base 24 through a motor base 26b and a motor base slide 260 and connected with said grinding wheel spindle 25 by means of V-belts 28, outer surface dressing means including a grinding spindle 30 rotatably axially supporting a rotary diamond dresser 29 for outer surface grinding of an outer surface grinding wheel 33 and its motor 31, and a feed box 32 secured to the base 23 for feeding the slide base 24 relative to said spindle means A. The outer surface grinding wheel 33 is always in contact with the rotary diamond dresser 29. When some of the bearings are gound, a skip dress counter provided in the power board 34 is actuated to move a dress cut device 35 mounted on the right side of the motor base 26b so that the outer surface dressing means 29 is moved closer to the grinding spindle 25 together with a dresser base 36. At the same time, grinding wheel correcting means (not shown) provided in the base 23 is actuated to slightly feed the slide base 24 towards the spindle means A. The numeral 37 in FIGS. 2 and 3 designates a grinder cover. As shown in FIG. 5, the grinding wheel spindle 25 is provided near its axial end with the outer surface grinding wheel 33 for grinding the outer surface of the workpiece and further has fixed to the same end a rotary diamond dresser 39 for dressing an inner surface grinding wheel 38. That is, the diamond dresser 39 and the outer surface grinding wheel 33 have in common spindle 25, the motor 27 and the like so that the construction can be simplified to that extent.  
  The grinding wheel spindle means. which is provided with the inner surface grinding wheel 38 for grinding the inner surface of the hollow workpiece 3, has such construction that the inner surface grinding wheel 38 invades into the steel pipe 3 held by the spindle means A and fed therethrough for the grinding operation. As shown in FIGS. I, 2 and 6, there is provided a slide base 41 which is slidable on a base 40 mounted on the bed I in a direction at a right angle to the axis of said spindle means A, said slide base 41 being made slidable by means of a feed box 42 and a feeding mechanism controlled thereby. Secured to the slide base 4] is a spindle base 45, which is provided thereon with a spindle slide head 44 to be reciprocated in a direction parallel to the axis of said spindle means A (ie, parallel to the longitudinal axis of pipe 3) by means of an inner surface grinding wheel indexing power-cylinder 46 secured to the spindle base 45, and a grin-ding wheel spindle 43 carrying the grinding wheel 38 is secured to said spindle slide base 44. The grinding wheel spindle 43, as shown in FIGS. 10 to I3, is provided with a front cover 102, which seals its front portion and facing grinding wheel 38. The front cover is formed with an annular space I03 therein. This annular space is formed by cut ting a peripheral channel in the inner surface of said front cover 102 and fitting a bushing I04 therein under pressure. There are provided several injection ports 105 opening into the front of the front cover and connecting said annular space with the front of the front cover. A liquid entrance passage 106 is communicated with said annular space 103, and a pipe joint I07 is connected therewith so as to introduce a high pressure grinding liquid into the space I03. The grinding liquid is injected immediately in front of the grinding wheel 38 from the injection ports 105. By properly selecting the diameter of the grinding wheel and the position of the injection ports 105, the grinding liquid is caused to adhere to the inner surface of the steel pipe 3 during inner surface grinding without rebounding on the side of grinding wheel and without striking against the grinding wheel diagonally, so that grinding efficiency may be promoted and the grinding liquid may effectively be used during the high speed grinding operation. The power-cylinder 46 is, as shown in FIG. 6, of a double cylinder type, and the position shown in the drawing indicates the dressing position of inner surface grinding wheel 38, and the position in which piston 47 is in contact with the front cover 49 of the inner cylinder 48 corresponds to the grinding position wherein the grinding wheel 38 invades into the steel pipe 3. In the position in which the inner cylinder 48 is in contact with rear cover 51 of the outer cylinder with the piston 47 being maintained in contact with the rear cover 50 of the inner cylinder 48, the grinding wheel 38 can be replaced by means of automatic grinding wheel exchanges 52a and 52h. In FIG. 7, a power cylinder 53 for the dressing operation is secured to the lower surface of the slide base 41, and the piston rod thereof is made integrally with the piston rod of a power cylinder 54 for reciprocating the slide base. This power cylinder 54 is integrally formed with a housing part 55 which is slidable on the inner surface base 40. A nut 56 of a feed screw mechanism is fixed in an axial direction to said housing part 55, and the rotation of a feed screw 57, controlled by the feed box 42, is changed into a rectilinear motion of the slide base 41 through said two power cylinders 53 and 54. The front bar feeder means E, which is provided with a rotary shaft parallel to the inner surface grinding wheel spindle 43, is slidably mounted on the slide base 41. That is, a feeder base 61 is secured to the slide base 41, a feeder slide base 62 is adapted to be reciprocated on the feeder base 61 by means of a first power cylinder 59 for feeding, and a feeder body 63 is adapted to be reciprocated on the feeder slide base 62 by means of a second power cylinder 64 for feeding. A motor 65 is secured to the feeder body 63 to rotate a feeder shaft 66 rotatably supported in the feeder body or spindle 63, the shaft being rotatable about an axis parallel to the longitudinal axis of the pipe 3. The first and second feeder power cylinders 59 and 64 are secured at right angles to each other to the feeder slide base 62, and the end of the rod of the piston 60 in the first feeder power cylinder is connected to an arm 58 secured to the inner surface base 40. The stroke of the first power cylinder 59 is the same as the maximum stroke of the power cylinder 54 for reciprocating the slide base and coincides with a reciprocating stroke of the front bar feeder means E, as hereinafter described, in a direction perpendicular to the axis of the spindle 4. Oil is simultaneously fed under pressure by the same change-over valve to said two power cylinders 54 and 59 which have same stroke as described above. In FIG. 7, when the first feeder power cylinder 59 moves leftwards relative to the piston 60, the piston 67 of the power cylinder 54 for reciprocating the slide base will move leftwards relative to the cylinder 54 and the inner surface slide base 41 will move leftwards. A stroke control device 68 is secured to the right end of the power cylinder 54. When the grinding wheel 33 is dressed as previously described and the grinding wheel spindle 25 comes near the spindle means A, a gear 69 of said stroke control device is rotated by a pulse motor (not shown) to rotate a screw 70. A shaft 71 and a sleeve 72 fitted therearound are moved leftwards by the same amount as the amount which said grinding wheel spindle 25 has moved, so as to shorten the stroke. Thereby, the clearance a between the inner surface grinding wheel 38 and the inner surface grinding rotary dresser 39 mounted at the utmost end of the outer grinding wheel spindle 25 can be maintained constant. The stroke length b of the dressing power cylinder 53 is made slightly greater than said clearance at so as to dress the inner surface grinding wheel 38. When the stroke of said slide base reciprocating power cylinder 54 is decreased, the axial center of the feeder shaft 66 is displaced sideways to provide a clearance equal to the amount of decrease in stroke between the piston 60 of the first feeder power cylinder 59 and the rear cover 73. However, the feeder slide base 62 is moved rightwards by the amount of said clearance by means of the first power cylinder 59 alone to avoid the deviation of the axial center of feeder shaft 66. This feeder shaft 66 is, as shown in FIG. 8, provided near the front end of the spindle means A with a magnetic chuck 74. A nosepiece 76 is mounted on the magnetic chuck and adapted to be attracted to the end surface of steel pipe 3 which is held and rotated by the spindle means A. The position of the chuck, that is, the position of the center of shaft 66, is such that the position in which the axial center coincides with the axis of the spindle 4 is made the reference or zero position in a path perpendicular to the axis of the spindle 4, and the terminal position of the path is a position in which the end surface of a bearing race held in the magnetic chuck is surfaceground by means of the grinding wheel spindle means D for surface grinding, hereinafter described. This zero position may be secured by reciprocating motion of the first feeder power cylinder 59, even if the return of the inner surface slide base is varied as described above. The second feeder power cylinder 64 is provided to effect reciprocating motion of the front bar feeder means in an axial direction of the spindle means A (i.e., parallel to the longitudinal axis of pipe 3). The second feeder power cylinder 64 is secured to the feeder slide base 62 and comprises a front cylinder and a rear cylinder 81, as shown in FIG. 8. The rod of piston 79 of the front cylinder 80 is secured to a member 77 which projects from the lower surface of the feeder body 63 so that the feeder body or chuck spindle 63 may be moved in an axial direction by moving the piston 79 through the front cylinder 80. The rod of piston of the rear cylinder 81 extends into the front cylinder 80, passing through a partition wall 84 which separates the front cylinder 80 from the rear cylinder 81, to limit the stroke of piston 79 of the front cylinder. The from bar feeder means E pulls the steel pipe 3 out of the spindle means A by reciprocating motion of the second feeder power cylinder 64 and after the outer surface grinding wheel spindle means B has completed cutting the ground end portion from the pipe to produce a bearing race (as described in detail later), the feeder means E transports the bearing race by means of the first feeder power cylinder 59 towards the grinding wheel spindle means D for plane grinding the bearing race end surface which is formed by cutting the end portion from the pipe to produce that bearing race. Furthermore, the piston 85 of the rear cylinder 81 is moved into contact with the rear cover 86 so that the stroke of piston 79 of the front cylinder may be increased to thereafter discharge the bearing race held in the spindle means.  
  Referring to FIG. 1, the grinding wheel spindle means D for plane grinding has the axis of its grinding wheel shaft perpendicular to the axis of the spindle means A, and is fed for the grinding operation on the bed I at a right angle relative to the axis of the grinding wheel, that is, in a direction parallel to the axis of the spindle means A. The surface grinding wheel spindle 89 is of the type having a built-in motor, and a surface grinding wheel 90 is ofa flat type and is formed by a dressing device 91 mounted on the front bar feeder means E. in FIG. 9, a plane base 93 is secured to the bed i, and a plane slide base 94 is adapted to be slidable on the plane base 93. The grinding wheel spindle 89 for plane grinding and a plane feed box 92 are provided on said plane slide base 94. The rotation of the plane feed box 92 is transmitted to a feed screw 97 through bevel gears 95 and 96, and a nut 98 for the feed screw is mounted in bearing in a housing 99 secured to the plane base 93. The slide base 94 is slided to effect inching feed and correction with respect to the grinding wheel spindle 89 for plane grinding. The numeral 75 in FIG. 1 denotes material feeding means and has a mechanism for initially feeding the steel pipe 3 into the spindle 4 of spindle means A until the pipe reaches the nosepiece 76 of the feeder shaft 66, which is in the forwardmost position.  
  The outer surface grinding wheel 33 and the inner surface grinding wheel 38 shown in FIGS. 13 to 17 will now be described. These grinding wheels are formedtype grinding wheels formed by means of rotary diamond dressers. The outer surface grinding wheel 33 for producing a bearing outer race comprises a grinding wheel part 33A for rough grinding, a grinding wheel part 33B for finish grinding, and a cutting part 33C. The cutting part 33C is located at the side of the grinding wheel part 338 apart from the grinding wheel part 33A and is extended from a chamfer grinding part perpendicularly relative to the axis of grinding wheel. There is shown in the drawing a grinding wheel provided with the grinding wheel part 33A for rough grinding and the grinding wheel part 335 for finish grinding, but an intermediate finish grinding wheel part may also be employed therebetween. The chamfer grinding part is perpendicularly projected from the cylindrical portion of the grinding wheel part 338, and a corner portion ofsaid cylindrical portion is formed to have an axially curvilinear surface to grind the chamfer. The dimension and shape of the grinding wheel part 33A and the grinding wheel part 338 are determined according to dimension and shape of the whole outer peripheral surface of the bearing outer race and the rough and finish grinding areas. When the grinding area is large, a grinding wheel part for intermediate-finish grinding provided between the grinding wheel part 33A and the grinding wheel part 333. The chamfer grinding part includes the cutting part 33C, a central chamfering part 330 between the grinding wheel part 33B and the grinding wheel part 33A, and a rough chamfering part 33E located on the other side of grinding wheel part 33A. The size of chamfering and depth of cut into the outer peripheral surface of steel pipe 3 are greater at the central chamfering part 33D than at rough chamfering part 335 However, it is so designed as to have same width between the three parts 33C, 33D, and 33E. The diameter 33a of the cylindrical part of the grinding wheel part 33A is smaller by the finish grinding thickness than the diameter 33b of the cylindrical part of the grinding wheel part 33B. The diameter of the cutting part 33C is determined so that the time for dressing of the cutting part 33C may coincide with other parts, considering the of thickness of steel pipe 3 to be cut, said chamfering parts 33D and 33E, diameters 33a and 33b of the cylindrical parts, and the like. FIGS. 15 and 16 illustrate an embodiment of a grinding wheel 33&#39; for grinding the outer periphery of the inner race of a ball bearing, which comprises a grinding wheel part 33A for rough grinding, a grinding wheel part 338&#39; for finish grinding, and a cutting part 33C in the same manner as grinding wheel 33. The shape of outer peripheral surface of the inner race includes a track channel and a seal surface so that it is more complicated than that of the outer race. The diameter of each part may be determined in the same manner as for grinding wheel 33. The width of rough chamfering part 33E is made to be wider than that of central chamfering part 33D and cutting part 33Cv However, the dimensions between the three parts 33C, 33D and 33E are equal each other, as in the case of grinding wheel 33. FIG. 17 shows a grinding wheel 38 for grinding of inner surface of an outer race of a ball bearing, which comprises a grinding wheel parts 38A for rough grinding and a grinding wheel part 38B for finish grinding. The dimensions and shape of said grinding wheel 38 are determined in a manner similar to those of outer surface grinding wheel 33. The outer surface and inner surface appearing in this embodiment of the invention indicate all surfaces and chamfers, including projections, hollows and the like present in the outer surface or inner surface. When the steel pipe is cut and ground by maintaining the rotary axis of grinding wheel parallel to the rotary axis of steel pipe 3 while using the grinding wheels as described above, end portions 3a and 3a of the steel pipe at the right hand of cutting parts 33C, and 33C shown in FIGS. l4 and [6, are severed to form bearing race units. Simultaneously, end portions 312 and 3b adjacent portions 30 and 30&#39; contact finish grinding wheel parts 338 and 338&#39; to be finish-ground, and at this time one side surface of the bearing race to be ground (the outer end of portions 36 and 36&#39;) is finished perpendicularly relative to the axis of the bearing race by cutting parts 33C and 33C. Furthermore, end portions 30 and 3c of the steel pipe adjacent portions 3b and 3b simultaneously are ground by rough grinding parts 33A and 33A. Thus, when the steel pipe 3 is successively fed in amounts corresponding to the length of one piece of product plus a cutting area, each of the end portions of said steel pipe 3 is successively rough ground, finish-ground, and severed to obtain bearing race units. This process of manufacture will be described in detail by taking as an example, the bearing outer race shown in FIGS. [8 to 21. An elongated steel pipe 3 of quenched and tempered bearing steel is fed so that a length suitable for two bearing outer races to be ground passes through the spindle. At this time, the nosepiece 76 on the front bar feeder means E waits as a stop for the steel pipe at the position shown in FIG. 18, and when the steel pipe 3 is chucked by the spindle means, the front bar feeder means retreats. Then, the outer surface grinding wheel spindle means B is moved toward the pipe along an axis perpendicular to the longitudinal axis of the pipe so that the outer surface grinding wheel 33 is fed perpendicu-