US2615371A - Milling machine and method - Google Patents

Description

Oct. 28, 1952 1-. s. SEE

MILLING MACHINE AND METHOD 6 Sheets-Sheet 1 Filed Feb. 10. 1948 Oct. 28, 1952 Filed Feb. 10, 1948 T. 5. SEE

MILLING MACHINE AND METHOD Hil 6 Sheets-Sheet 2 w flue/2287 A jeaaoreijee Oct. 28, 1952 1-. 5. SEE 2515,1371

MILLING MACHINE AND METHOD Filed Feb. 10, 1948 6 Sheets-Sheet 3 Oct. 28, 1952 'r s 555 2,615,371

MILLING MACHINE AND METHOD Filed Feb. 10, 1948 6 Sheets-Sheet 4 Oct. 28, 1952 T. 5. SEE

MILLING momma AND METHOD Filed Feb. 10, 1948 0 n Nw 1 illl;

A i Y 1 W W M M @w wm Patented Oct. 28, 1952 Theodore S. See, Hammond, Ind., assignor to La Salle Steel Company, Chicago, 111., a corporation of Delaware Application February 10, 1948, Serial'No. 7372 v.2 Claims. (01. 90 15) This invention relates to a new and improved method of milling metal work pieces and to a new and improved machine capable of practicing the method. The ,termfmilling, as employed herein, indicatesa planing action 'by a cutter on metal. v l

Heretofore, in the milling of steel work pieces, such as bars and the like, it has been common practiceto employ a single point tool, held in a stationary position, and to rotate the bar, While. at the same time feeding it lengthwise, to cause the tool. to progress from one end of the bar to the other. tensively used, is subject to the fundamental onjection that it is'slovv and laborious. That the operation mustbe slowis necessitated by the fact that the cutting tool is constantly in contact with the metaland the chip being removed from the bar constantly flows over the tool thereby tending to heat and wear itunduly. Wearing or chipping of the tool results, of course, in shut down of the machine and regrinding of the tool. If "increased speeds are, employed in conjunction with such a cutting tool, increased wear anddeteriorati'on results, necessitatingmore frequent shut downs and regrindings.

In milling" flat metal surfaces on the othe hand,'as described in aseries of articles appearing in the 1947 issues-of Iron'Age, it has been customary'to employ What is termed; a face cutter in which a plurality of blades made of high speed cutting steelzor carbide are mounted in a'cutter'body, by means of .wedges and screws; and gthe cutter is then rotated and moved over the face 'of the work piece in such ,a manner that all of the blades are constantly in contact'with the Work. Here again the chip load on each blade is substantial and-the operation is again subject to the fundamental objection that itis slow' and laborious. In computing the work speed ofacutter of this type it has been cus; tomary'to refer to the surface foot rate which is computed by employing the equation:

in which dis the diameter of the cutter, in feet; and R, P; lL'represents the speed of rotation of the cutter, and S. F. -M; represents the surface foot rate expressed in feet per minute; Heretofore in milling steel and steel alloys it has been Such an operation, while eX rates substantially below 1000 feetperminute. Itrwas the discoveryof the so-called hardmet,- als, such as tungsten carbideand other sintered carbide materials including tugnstentitanium carbide that 'permitted'the successful milling ;of

steel and its 'alloys, particularly in the heattreated state, at speeds higher than those employed with highspeed steel tools.

With the foregoing desiderata in mind, .the present invention has for an important object thereof, the millingofsteel and alloy-steels at speeds substantially in :excesswof 'those heretofore employed and previously'considered possible. Whereas the art teaches'that, the speed of the cutter and the rate "of movement of the cutter blade must be limited in order to obtain thexbest results,i=it has now, been: discovered that through the employment" of speeds vastly-in excesslof' those previously deemed-possiblethe ,life of the cutter is prolonged, improved work finishes are obtained, the wear on the cutter is reduced to the point where it is practically negligible-and the time required to perform agiven piece of Work is sharply reduced to -*a' minimum, The practice of'this neW- method is intimately associated with the shape and construction/of the cutter itself for it must be appreciated that not all cutters, of any and all designs, will operate successfully at these vastly increased speeds. Thus it has been discovered that thecutten-ima'de of hard metal such as alloys of carbides, bori'des, nitrides, or silicides, must be, provided with-a maximum or a near maximum number of teeth or cutting blades-positioned-in close proxim-ity with one another, whereby the pitch; i. ':e., the distance from one cutting edge tothe next adjacent cutting edge, is reducedto .a minimum .or near minimum, and-the cutter is rotated at speeds greatly in excess of those heretofore employed. Accordingly, in practicing the present invention, the screws and wedges of the prior art'cutters are eliminated because they require the. teeth to be spaced too far apart to permit their use for the purpose intended.

'As disclosed herein the teeth, formed'ofhigh speed'ste'el, for operation atlower speeds, but substantially above the. speed range previously employed in milling steel, particularly steeland steel alloys, or preferably of so-calledhard metal of sintered carbide materials are ground or cut into the cutting face of a monolithic cutter in such a manner as, to produce a low or minimum pitch and a maximum or near maximum number of teeth in the peripheral ,face of the; cutter. Cutters of this character, operating at high speeds, at rates far in excess of those heretofore employed, have been discovered capable of increasingthe rate of milling on a bar of steel from, for example, 90 inches per minute to 900 or even 1800 inches per minute. The chip load on the teeth is maintained at reasonable values efiective to insurea satisfactory cutter life and fatigue in the cutter iseliminated. Employing such cutters at these extraordinarily high speeds will, in many instances, result in a noiseless operation in which the cutting action takes place too rapidly to be visible to the naked eye and only by the accumulation of chips and the improved appearance of the metal can it be observed that the milling operation is actually tak-' ing place.

As indicated above, the present invention has for another important object thereof, the provision of an improved machine capable of performing the improved method. As disclosed herein the invention is embodied in a machine for turning metal bars, inwhich the bar, rigidly held against radial vibration is fed lengthwise between a'plurality of cutters constructed in'accordance with the principles recited herein, and thecutters are constructed and arranged to rotate about their own axes at the high speeds mentioned and at the same time revolve bodily, in -a planetary motion around the bar being milled. It will be appreciated however that the method of the invention may be incorporated in machines of other design and construction without departing fromthe spirit of the'invention as set forth inthe appended claims. 1

Other objects and features of the invention will become apparent from a reading of the following specification in thelight of the accompanying drawings, inwhich,

Figure 1 is a front plan view of a machineconstructed in accordance with the present invention; 1

Figure 2 is a view similar to Figure 1, showing a suction fan applied to the machine of Figure 1 for the purpose of chip disposal;

Figure 3 is a diagrammatic end View of the machine showing the arrangement of the suction fans; I a Figure 4 is a view in section of the cutter assembly;

' Figure 5 is a view in section taken substantially along the-line 5 5 of Fig.1 showing the cutter and motor mountings;

Figure 6 isa detail view, in section, of the adjustable work-piece bearing taken substantially along the line 65 of Fig. 1;,

Figure 7 is a detail, top plan view, in section, of the bearing shown in Figure .6; and

Figures 8 to 12 inclusive are views of cutters. Asshown in the drawings, the reference numerals l0 and I2 indicate standards arranged to support the milling machine which is indicated generally by the numeral l4 (Figure 1). Extending through openings formed in the standards l0 and I2 are a plurality of hollow supporting shafts l6 and I8 provided with hub portions 20, 22 having flared, web-like members 24, 26 formed integrally therewith and joined at their opposite extremities to a hood or casing 28 within which the cutter assembly is located.

' In general, the cutter assembly comprises, as shownin Figures. 1, 4 and 5, a pair of electric driving motors 40, 42'located at the left, or entering, end of the machine, as shown in Figure 1, and a second pair of driving motors 44, 46 positioned at the right or exit end of the machine.

These motors, which are provided for the purpose of rotating the cutters about their own axes, are pivotally mounted upon the hood or casing by means of pins 50 and are each provided with a driving member 52 having driving engagement with driven member 54 (Fig. 4) keyed to pins 56 whichform a part of the shaft assemblies for supporting milling cutters '60. Removable couplings 62 are inserted in the cutter shaft assembly to permit ready removal of the cutters from the machine for purposes of grinding or replacement by cutters of other shapes orsizes.

The cutters 60 are keyed to spindles 64 which form the central portion of the cutter shaft assembly and are held in position bymeans of lock nuts '66 having screw threaded engagement with the spindles.

As shown in Figures 1, 5 and 6, the hood or casing 28 is S-shaped in cross-section to provide a plurality of oppositely facing trough-like members or pockets into which the motors 40, 42 and 44, 46 are mounted. In accordancewith the in vention the S-shaped hood or frame 28 is mounted for rotation within the standards I0, I2 and to this end'a driving member I l, which is shown; as comprising a chain or belt, is connectedzwith a suitable source of power (not shown). Thus, in operation, the casing or frame 28 rotates carrying with it the motors and the cutter assemblies, as a result of which,it will be under stood, the cutters, driven by the motors 46, 42 and 44 are caused to rotate, or spin, about their own axes and simultaneously'move in a planetary path around the work piece or bar A which extends lengthwise, centrally, through the machine.

In order to provide suitable support for the bar A during the machining or milling operation, and to prevent undue vibration of the bar with respect to the cutters, bearing or supporting assemblies indicated generally by the ref-' erence numerals 10, 12 in Figure 1, and shown more specifically in Figures 6 and 7, are provvided. As shown in Figure 1, one such bearing or supporting assembly is located adjacent each end of that portion of the bar being milled and, as shown in Figures 6 and '7, each assembly comprises a plurality of roller bearings 14, 16 having engagement with the bar or work piece A at spaced points. The bearings 14, 16 are mounted in a housing 18 that is slidably mounted by means of mounting blocks on the frame or casing 28 'of the machine and thereby revolve with the frame or casing about the bar or work piece A. An adjusting screw BZ-equipped with a hand wheel 84 is provided for the purpose of moving the housing 18 to the right or to the left of the position shown in Figure 6.

The rolls '4 are mounted on the housing 18* and thus movement of the housing results inmovement of the roller'bearings 14 towards or awayf rom the axis oit the work piece A. In order" to move the cooperating bearings 16 towards or away from the axis of the work piece, independently of the bearings 14, to accommodate bars of various diameters, the said bearings 16 are mounted, within the housing 18, on a sleevelike member 88 that is arranged to slide back and forth within the housing. The sleeve 88 is pivotally mounted on the extremity of an arm 90 arranged to extend through a hollow, tubular member 92. The sleeve 88 and the arm 90 are urgedcto the left of the position shown in Figure 6 by means of a compression spring Q4, but may be adjusted in either direction, to the right or'left, by means of a hand wheel 96 1 d ily adjustedto accommodate pieces of different diameters. Similarly, it will be appreciatedthat in order to operate on bars of difierent diameters, or to' mill orxmachine the work piece to different depths, it willbe essential that the cutter assemblies. be mounted in sucha manner thatthe distance between the cutter faces may be increased ordecreasedand tothis end,as shown in Figure 5, the motors *44; 46 are mounted in frame members H0, H2.

which, owing to theirshape, .may'be referred to as baskets. The inner ends offrame members H0, H2 have bushing portions H4, H6 formed -integrally 'therewith .and these bushings have bearings H8, 12!! mounted within them forthe purpose-of: supporting the ..pins. 56 which are connected through the coupling 62 to thespindles I 64 upon. which ethecntters .60; are, keyed..-j Adjusting-wheels 122, 124 are secured Ltothe frame 28 and-are pivotallysecured, by means of rods 126; [28 to-the: basket frames H0, H2 in such a mannerthat'rotation of the wheels shifts the position of the .motors and the basket frames about the pivotal points .5ll'to cause'the bearings [18, l20.:to' move towards or away" from one 'anothen-forthe purpose 10f avarying the distance between the cutters1 60.1"Thus theldistance between the cutters may beaccurately regulated toaccOn'1modate 1 work: pieces of different sizes orisha'pesl s F'For the: purpose. of affording additional sup.- port toxthe cutterszfiu. in ordertoudecrease or eliminate vibration, ladditional bearings I2 I, 123 are provided: and,..as :shown in' Figure 4, these are: disposedon opposite sides of the cutters 0 and are arranged to"encirc1e'the=.cutter spindles I 64. Theserbearings' are supported in such a manner as to facilitate removal of the cutter assemblies to permit regrinding or replacement and to this end the bearings are .carried by plate members I30, 132' (Figure l) which, by means :o'fbolts 134 and adjusting screws. 136 are rigidly secured to decks I38, I40 forming parts of the baskets H0 and! I2. In operatiom-the couplings 62 may be disconnected,following which the plates I30, I32-may be readily removed, carrying with them' the spindles 64 and'the cutters 60 whereupon new "cutters" may be installed or thecutters ,reground and the plates put-back on themachine and the couplings connected. At this point it may be-mentioned that the bearing assemblies =10 and "ll-for the workpiece, one of which is shown in Figures -6 and 7, engage the work piece A- at locations which may be defined as between the. lock-nuts '66 and the bearings I.2l,' .m, .theretlbeing-sufficient room provided. at these locations to permit the narrowhousing 18, shown in Figure '7, to be accommodated for this purpose- During the milling operation chips of metal will be removed from the work piece by the cutters 60 and to provide for the removal of these .greater accuracy and better finish. f

6 chips from the machine; a pluralitynof suction fans I44, I46 are carried by the main-frame=28 of the machine for rotation therewith. This arrangement' is shown inFigures 2 and 3 in which the motors are provided with intake ducts i150, t52sextending to points in close proximity to the cutters 60 andwith discharge ducts I 54,l156-leading to points that are remote from the cutters, whereby the suctionproduced bythe fans keeps the machine free of chips and dust. A circular trough, surrounding the machine, or any other suitable arrangement maybe-provided for-receiving thechipsas they emerge from'the ducts I54, 156. At thispoint it will be appropriate to point out that the milling operation for which this-m'achine is intended will ordinarily be a dry operation, i. e., one requiring no special lubricant or lubricating system, owing to the factthat the cutters are formed of a carbidematerial; -such as carbolo'y,-and'revolve at such high speeds that there is no need for alubricant. I? 1 Turning now to the *cutters themselves, as shown in Figures 8 to 12 inclusive, it has already been explained that in accordance with, the

present invention the'cutt'er is'provided with a maximum or near maximum 'ofcuttingt'eeth-of minimum or near minimum pitch. The teeth may be in the form of straight lines extending parallel to the axis ofthecylinderorthey'may preferably take the form of a'spiralor helical tion, a three-inchste e'l bar-may besatisfactorily milled by means of a cutt-erhaving a fourfinch diameter and a pitchi'of one-eighthinch. The

depth .oi-the teeth may likewise vary-but ordin'ar ily'it will correspond"approximately to the pitch of the teeth, theimportant consideration being the'space between the'teeth should be sufficient to receive the chip formed by the action of'the cutting edge on 'thework pieces .Boththe machine and the cutterdisclosed herein are'd'esigned and constructed for operation at highspeeds: at

speeds greatly in excess of those heretoforeem ploy'ed. Thus, ii the cutter is made of high-speed steel the blades,1:in practicing theinventiomwill move at a speed in excess of 500 feet per minute andif made ofcarbide'materials, or other hard metal such as tungsten carbidejtungsten titanium carbide oricarboloy. at aspeed in excess of 1000 feet per minute. "Thespee d of movement of the "cutting tooth'or blade may" be computed by the formula 1'rd, R. P. M.=S. F. M. Owing to the fact'that each tooth or cutting 'b'ladeh'as only instantaneous contact with the work piece and is then out of contact therewith for a much longer I time than it has been in contact, fatigue or wear of the cutteris reduced to a 'rninimum.'.' Also, owing to the high speed of rotation oi thecutter, an infinite number of fine cutting operations are imparted to each small surface .area of the work piece, resulting in 'the production of piecesfo f .The linear speed of the work piece withv respect to the cuttercannot be precisely stated owing to the factthat it will'depend ,onJsuch factors .as the width 'of 'the cutter and the physical characteristics of the work piece but in any event the invention here also contemplates the employment of much higher speeds than heretofore. Thus a three-inch bar may be fed past the carbide cutter at a linear speed of or even 200 feet per min- 7 ute, an accomplishment heretofore unknown ,to those skilled in the art.

vThe cutter may be monolithic in character in which event the teeth or cutting blades will be ground into the exterior cylindrical face of the cutter or it may be built up as, for example, by having the carbide teeth or blades brazed to the cutter body; the important aspect in the design andconstruction being the low pitch, greater number of teeth and abnormally high speeds. As stated, the pitch of the teeth or cutting edges may vary depending upon such factors as the size of the cutter and the physical characteristics of the work piece, but ordinarily the pitch will lie within the range of from inch to inch. Each individual cutting edge or tooth may .be ground or shaped to any desired configuration, to provide clearance, etc., in accordance with the teachings of the prior art.

Although the invention is shown and described herein as embodied in a specific type of machine designed to mill bars, it will be appreciated that the invention, in many of its aspects, may be incorporated in machines of diiferent design and construction. Thus it is contemplated that the barmight be rotated with respect to the cutter, or the bar might be held against lengthwise movement and the cutters arranged to move lengthwise of the bar. Similarly if it is desired to practice the invention on work pieces other than bars, the machine can be designed to accomplish this purpose without departing from the scope of the inventionas set forth in the appended claims. Changes and modifications may, of course, be made in the machine illustrated by those skilled in the art, in keeping with the spirit of the invention as herein set forth.

Furthermore, the machine and method, al-

though primarily intended for use in the milling .A typical milling operation which can be satisfactorily performed on the machine may be described as follows: a cutter driven at an R. P. M. of approximately 1500 and having a diameter of approximately 4 inches mills a round bar to a depth of approximately 3 2' of 'an inch. .The rate of feed between the round bar and the cutter during this operation is approximately 600 inches or 50 feet per minute. This operation is performed, with a cutter having a inch pitch and a 22 /2 degree helix, on cast iron having a Brinell hardness of 200, or steel of the grade C 1020 having a Brinell hardness of 180. It is to be understood that the helical angle of the teeth may vary but ordinarily it will lie within a range of from degrees to 30 degrees. The teeth themselves may be provided with a radial angle of any desired degree and the cutting faces thereof may, in accordance with the teachings of the prior art, be provided with a desired negative rake angle to assure proper chip disposal.

' Finally, although the machine disclosed herein is intended primarily forthe millingof-round bars, it will be appreciated that the invention,

including the method, contemplates the milling of other steel and alloy steel products such, for example, as billets, slabs, blooms, rounds, tube rounds, and bars of all shapes as;.well as ap-; paratus, articles, devices and equipment manufactured from such products. 1

Having thus describedmy ,inventiomwhat-I claim as new and desire to secure by Letters Patent of the United States is: 1 1

1.- A machine for milling metal at-high speeds comprising, in combination, a rotary frame; a plurality of frame members pivotally mountedon said rotary frame, a plurality of motors carried by said frame members, a plurality of cutters respectively mounted on said framemembers and driven by said motors, means for independently adjusting said frame members about the'pivotal mountings thereof to adjust the position of the cutters with respect to one another, a plurality of bearing assemblies disposed axially of and onDD- posite sides of the cutters for rigidlysupporting the work piece,v and means foruadjusting the bearings in said assemblies with respect to. one another, whereby work pieces of diiferent sizes may be accommodated by the machine-;. 1

2. A machine for milling metal at high. speeds comprising, a rotary frame, means for rotating said frame, a plurality of frame members pivotally mounted on said frame, a plurality of motors carried by said'frame members, a "plurality of cutters driven by'said motors andrespectively mounted on said frame members on opposite sides of the axis of the work piece to be milled, means associated with each of saidframe members for adjusting said frame members about the pivotal mountings thereof to adjust said cutters toward and away from said work axis, a plurality of bearing assemblies located adjacent said cutters and each including work engaging bearing.

means disposed on opposite sides of said work piece axis for rigidly supporting thework piece against sidewise movement as it is fed :through the cutters, and means included-in each of said bearing assemblies for simultaneously adjusting the bearing means on both sides of said work piece axis and for independently adjusting the bearing means on one side of said work piece axis relative to the other bearing means to accommodate work pieces of different sizes.

. THEODOR s. SEE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS v Date

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