US2881507A - Milling cutters - Google Patents

Description

April 14, 1959 T. s. SEE ETAL 2,381,507

MILLING cUTTERs Filed Feb. 24. 1953 5 sheets-sheet 1 38 INVENToRs:

Theodore S. See Homc'eAJ''a/nmel BY l v April 14, 1959 v T. s. SEE ET AL 2,881,507

MILLING CUTTERS Filed Feb. 24, 1953 4 3 Sheets-SheetI 2 Horacefl f-omrrz eZt April 14, 1959 T. s. SEE ET A1. 2,881,507

MILLING CUTTERS Filed Feb. 24, 1953 :s sheets-sheet :5

Q75? /N VEA/70kg:

Theodore S. See Horace? .'ommel United States Patent O MILLING CUTTERS Theodore S. See, Hammond, ind., and Horace A. Frommelt, Milwaukee, Wis., assignors to La Salle Steel Company, Chicago, Ill., a corporation of Delaware Application February 24, 1953, Serial No. 338,392

3 Claims. (Cl. 29-105) This invention relates to milling cutters and more particularlyn to new and improved cutters that are capable of performing high speed cutting operations without undue wear or breakage and which are susceptible of being reconditioned with a minimum expenditure of time and effort.

While cutters embodying the present invention are not limited thereto, they are particularly designed for and are highly useful in carrying out high speed machine operations of the type described and broadly claimed in Patent No. 2,581,449 issued January 9, 1952, in the name of Theodore S. See and entitled, High Speed Machining of Ferrous Materials. As explained in the See patent, it was, prior to the invention therein disclosed and claimed, considered uneconomical and impractical, if not impossible, in the metal removal art and, particularly, in the machining or milling of ferrous work pieces to operate the cutters relative to the Work at speeds as high as would be desirable because of the destruction or undue Wear of the cutters after relatively short periods of operations at such high speeds.

In machining ferrous work pieces utilizing the methods disclosed in the See patent identified above, the cutters are operated at surface foot rates far in excess of anything theretofore believed possible, are provided with greatly increased numbers of cutting teeth by virtue of the employment of a much smaller tooth spacing or tooth pitch than was theretofore believed practicable, and are so constructed as to eliminate the tooth vibrations theretofore thought to be inevitable. Consequently, by the combination of these factors and by employing work piece feed rates corollated to the increased surface foot rates and minimum tooth pitch so as to maintain the proper chip load, a machining operation may be conducted at extraordinarily high speeds without reducing or shortening the cutter life. However, in view of the high operating speeds, it is necessary that milling cutters be designed and provided which will eliminate the tendency of the cutting elements to be displaced from the milling head in response to the large centrical forces produced by the high speed rotation. This tendency to be displaced is aggravated in the construction and operation of milling heads of large diameter, particularly when it is considered that all of the above criteria with respect to improved operating characteristics must be fulfilled.

Accordingly, one object of this invention is to provide a milling cutter having cutting teeth or elements mounted on the cutter body in such a manner as to minimize deleterious vibrations and having a predetermined minimum pitch to permit operation at surface foot rates heretofore believed to be impossible.

Another object is to provide an improved milling cutter in which each of a plurality of segmental or individual cutting elements may be rmly secured in an adjusted position, and in which it is possible to remove the cutting elements for reconditioning with a minimum expenditure of time and effort.

A still further object of this invention involves the 2,881,507 Patented Apr. 14, 1959 provision of a milling cutter head in which the segmental cutting elements thereof are both positively secured against displacement from the head in response to centrifugal force and also mounted so as to be free from undesirable vibratory forces.

Another object of this invention is to provide a milling head of large size and light Weight which is adapted to be operated by a high horsepower source of rotary motion.

A still further object of this invention is to provide a milling cutter utilizing a plurality of cutting elements each of which is provided with a plurality of cutting teeth so as to provide a cutter capable of removing large amounts of metal at surface foot rates which are low in magnitude although within the range of surface foot rates prescribed by the above identified patent.

In accordance with one embodiment of the invention, a milling cutter is provided which includes a supporting member or circular plate to which is secured at a spaced axial position, a clamping plate having an annular ange formed integral with and extending from an inner surface of the clamping plate` A plurality of segmental cutter elements are positioned on the supporting means adjacent the periphery thereof in an abutting relationship and each of the segmental elements is provided with an arcuate slot so that when the plurality of segments are disposed in the abutting relation, a single circular slot is formed, within which is received the extending ange of the clamping plate. A plurality of machine bolts journaled in the supporting means are utilized to move the clamping plate relative to the supporting member so as firmly to engage the plurality of segments and hold them in their adjusted position. A carbide block or insert having a plurality of cutting teeth formed therein is secured to each of the segmental elements to provide cutting edges adapted to engage the workpiece. Each of the segmental elements is also covered with a vibration damping material to prevent vibratory destruction of the cutting edges formed on each of the carbide inserts.

In second embodiment of the invention the clamping plate is provided with a plurality of individual extending tapered portions and the cutter elements are interposed between the supporting member and the clamping plate with a tapered slot formed in each of the elements in engagement with an adjacent tapered extending portion. Means are provided for moving the clamping plate into wedging engagement with each of the plurality of cutting elements to hold these elements in a desired position. Also, each of the cutting elements, which is coated with e ICC a vibration damping or absorbing material, is provided `ing tapered ngers which are adapted to engage the tapered sides of adjacent cutter elements so that upon movement of the clamping plate towards the supporting plate, the cutter elements are wedged into engagement with both the tapered fingers of the clamping plate and the upper surface of the upstanding lugs formed in the supporting plate. Also, each of the cutter elements is mounted in a vibration damping and absorbing material to prevent vibratory destruction ofthe cutting edges.

For a more complete understanding of the invention referenceshould now be had to the drawings in which:l

Fig. 1 is a cross sectional view of `one embodiment of a milling cutter of this invention;

Fig. 2 is a fragmentary front elevational view of the milling cutter shown in Fig. 1;

Fig. 3 is a fragmentary top, plan view of the milling cutter shown in Fig. 1;

Fig. 4 is a perspective view of a'carbide cutter insert provided with a plurality of teeth;

Fig. 5 is a perspective view of a segmental cutting element `adapted tocarry the insert shown in Fig. -4;

Fig. 6 is Va cross sectional view of the assembled segmental cutter element and insert therefore;

Fig. 7 is a fragmentarysectional view of a second embodiment of the invention;

Fig. Stisa fragmentary front elevationalview, partially broken away, showing the milling cutter lof Fig. 7;

Fig. 9 is an enlarged fragmentary-elevational view of al portion of afclaxnping vplate utilized in the cuttershown in Fig. 7;

Fig. 10 is a front lelevational view of a segmental cutter element having'a carbide insert Witha plurality of cutting teeth formed therein;

Fig. 11 is a cross sectional view of the cutter element shown in Fig. 10;

Fig. 12 is a fragmentary side elevational view of a third embodiment of the invention;

Fig. 13 is a fragmentary face view, partially broken away, of the cutter shown in Fig. 12;

Fig. 14 is an enlarged perspective view, partly in section, showing a cutter element in operative position in the milling cutter shown in Figs. 12 and 13; and

Fig. 15 is a sectional view of the cutter element shown in Figs. 12 to 14, inclusive.

Referring now to the drawings wherein like reference numerals indicate the same elements throughout the several views and, more particularly, to Figs. l to 6, inclusive, yof the drawings, vthe invention is shown as embodied in a milling cutter generally indicated as 20. The cutter comprises a circular supporting plate 22 to which is detachably secured a clamping plate 24. The plate 24 cooperates with the plate or supporting member 22 to clamp a plurality of segmental cutting elements 25 comprising a body portion 26 anda cutting insert 28 therebetween.

To clamp the cutting elements 25 in an adjusted position adjacent the periphery of the plate 22, the clamping plate 24 is provided with an integral annular ilange 30 which extends inwardly toward the plate 22. The Bange 30 Yis adapted to cooperate with a plurality of arcuate slots 32 formed in the body portions 26 of the segmental cutter elements 25. When the plurality of elements 25 are positioned in the desired relationship about the periphery of the plate 22, the plurality of slots 32 form a single continuons annular slot 33 (Fig. 2) in'which is received the'flange 30.

.To secure the flange 30 and slots 32 in this cooperating relationship, the plate 24 is threadedly engaged by a plurality of keeper bolts 34. ,The headed ends of the bolts 34 are rotatably received within a plurality of counterbores 36 formed` in the plate 22 so that rotation of the bolts 34 moves the plate 24 in an axial direction and to the left, as viewed in Fig. 1 of the drawings, to rigidly secure the plurality of segmental cutter elements 25 in the desired position.

To provide an increased number of cutting teeth and, accordingly, an increased speed of operation free from undesired vibrations, each of the carbide inserts 28 is formed with a Yplurality ,iofindividual teeth 38 -which may :be Aformed by, grinding the inserts, 28 withA suitable means such asta diamond particle grinding 'wheelhaving its-'grindingsurfaces formed atanglescorresponding to the angle to-be provided between yadjacent faces `of the teeth 38. The inserts 28 are secured'tol upper surfaces 4l)l ofthebody portions '26-byany suitablemeans, such the inserts. A vmore economical method of providing the teeth 38 is to produce these teeth in the carbide insert 28 prior to the sintering or heating of the insert necessary to form the iinally hardened article. Thus, the only expensive grinding operation required is the iinal finishing of the teeth for dimensional correctness for both pitch and the included angle between teeth. Since only the insert 28 is formed of the expensive carbide material, the cost of the cutting element 25 is obviously very small, and the provision of a method whereby only a small block of carbide is required also decreases the initial cost of producing the segmental cutting elements 25.

In order to prevent the deleterious etects of vibration on the cutting teeth 38, the body portion 26 is covered with a vibration damping or absorbing material 42 such as Selectron- If desired, the damping material 42 may also be applied to the surfaces of the ange 3G and to the surface fof the plate 22 with which the segmental cutter elements 25 are placed in contact.

Basically the Selectron resins are composed of (a) a polyester of a glycol with an ethylenically unsaturated .polycarboxylic acid or a mixture of such acid and a polycarboxylic acid free of ethylenic unsaturation and (b) a compound polymerizable therewith and containing a CH2=C group. Selectron is a thermo-setting, unsaturated polyester resin which possesses little or no resiliency when cured by the application of heat and the addition of a catalyst. Since Selectron possesses a thermo-setting characteristic, any heat generated in the cutter 20 during the milling operations serves to strengthen theinternal structure of the damping material 42 and to prevent distortion of this material with its attendant reduction in damping qualities. Solectron is sufciently strong to provide a secure mounting for the teeth 353 because it has a compression strength of 21,000-23,0tl p.s.i., a tensile strength of 7,000-8,000 p.s.i., and a modulus of elasticity in exure of 5.5 l05 p.s.i. This damping material also has a low linear coeilicient of thermal expansion, 4-5 105 inches per F., so that the heat produced by operation of the cutter 20 does not produce undesired internal stresses or displacement of the teeth Selectrous freedom from damage due to shock or impact is evident from its Barcol hardness rating of 45-50, a Rockwell M Scale hardness rating of 11G-115, and a notched Izod impact strength of .17 foot-pounds.

In order to facilitate rotation of the milling cutter 20, the plate 32 is provided with a centrally located opening t4-adapted to receive a power shaft (not shown) and is also provided with a .keyway 46 opening into the aperture 44 to facilitate a spline interconnection between the plate 22 and the driving shaft.

A commercial form of this embodiment of the invention could comprise, for example, a cutter having a 131/4 inch diameter with 654 teeth to provide a tooth pitch of 1,66 of an inch. Assuming a chip load of .005 inch per tooth, or for 654 teeth, a chip load of 3.27 inches per revolution, the inches per minute of removal may be set well within thefrange embodied in the See machining technique described in the above identilied patent. Again assuming that 'the i.p.m. utilized in this particular application is 1200 inches, it is obvious that the r.p.m of the motor fdriving the cutter 20 can be reduced below 500 revolutions per minute so that the surface foot rate for the cutter 20 will not exceed 1500 `feet per minute. It is believed to be impossible to achieve such removal rates .with the existing types of milling cutters and still maintain a suitable finish on flat components.

Inoperation, the plurality of cuttersegments 25 are disposedabout the periphery of the plate 22 in an abutting relationshipwith the plurality of grooves 32 in such 'a positionas to' form the single continuous annular groove 33. 'The clamping plate 24 is then placed on the cutter elements 2S with the ange 301in engagement with the as -brazing, after `Vthe teeth' 38-haverbeen generated. Lenie@ groove`l33. iheplatelztis securedin this :position `by engaging this plate with the plurality of machine bolts 34 and tightening these bolts to clamp the plurality of elements 25 in the desired position. n

When it is desired to replace or recondition one or all of the cutter elements 25, the machine bolts 34 are loosened to permit a disengagement of the annular ilange 30 from the groove 33, at which time the desired element or elements 25 may be removed and sharpened by utilizing a jig of proper construction and a diamond grinding wheel. The reconditioned cutter elements 25 are then replaced in the manner described above.

A second embodiment of the invention, shown in Figs. 7 to 11, inclusive, of the drawings comprises a milling head or cutter 59 which includes a circular supporting plate 60 similar to the plate 22. A plurality of segmental cutter elements indicated generally as 62 (Fig. 10) are disposed about the periphery thereof and secured in this desired position by a clamping plate 64 which is secured to the plate 60 in spaced relationship by a plurality of machine bolts 66.

The segmental cutter elements 62 comprise a body portion 68 to which is secured an insert or block 70 of a material. such as carbide in which are ground a plurality of cutting teeth 72. The body portion 68 of the cutter element 62 is provided with a tapered slot 74 which tapers inwardly and downwardly from an upper surface of the body portion 68. The body portion 68 is also formed with an offset (Fig. so that when a plurality of elements 62 are disposed in an abutting relationship, a shoulder 76 of the inner portion of the body 68 engages a shouldered portion 78 formed in the outer portion of an adjacent element 62. Because of this novel interlocking relationship between the plurality of adjacent cutter elements 62, each of these elements is prevented from being displaced outwardly due to the centrifugal force produced by high speed rotation of the plate 60.

The plurality of cutter elements 62 are secured in a desired position relative to the supporting plate 60 by means of a plurality of wedge shaped or tapered lugs 80 formed integral with an inner surface of the clamping plate. 64. The depending lugs 80 are positioned adjacent the outer periphery of the plate 64 and are spaced from each other by a distance equal to the distance between adjacent slots 74 when the segments 62 are properly arranged adjacent the outer periphery of the plate 60. As shown in Figs. 7, 8 and ll of the drawings, when the clamping plate 64 is superimposed upon the plurality of annularly arranged elements 62, the plurality of lugs 80 are wedgingly received within the plurality of slots 74.

In order to positively secure the element 62 in this desired position, the machine bolts 66 are tightened to move the clamping plate 64 axially inward toward the supporting plate 60, and, in doing so, urge each of the tapered lugs 80 into intimate engagement with the tapered inner walls of the slots 74.

In order to prevent vibratory destruction of the teeth 72 formed on the carbide inserts 70, each of the depending lugs 80 is coated with a vibration absorbing or damping material 81 such as Selectron. Also, the entire body portion 68 of the cutter element 62 is coated with this vibration damping material so that each of the cutter elements 62 is' mounted in a vibration damping manner with respect not only to the clamping ring 64 but also to the supporting plate 60.

As shown in Fig. 7 of the drawings, the teeth 72 are not only provided on the outer edge of the block 70, as indicated by 82, but also on an outer surface 84 thereof. Thus a high speed cutting element 62 is provided having a plurality of closely spaced cutting teeth 72 formed integral with a single block of carbide 70. The provision of the plurality of teeth 72 on each of the blocks 70 provides a segmental cutter element 62 having teeth spaced at a minimum pitch so as to provide a cutter element adapted for use in the high speed milling techniques described and claimed in the above identified See patent.

To provide a means for rotating the milling cutter 59, the plate 60 is provided with an aperture 86 and a slot 88 which are adapted to receive the end of an actuating shaft or spindle. Obviously, the plate 60 may be provided with any other type of engaging means for the purpose of securing the milling cutter 59 to a source of rotary actuation.

In operation, the plurality of cutter elements 62 is positioned Vadjacent the outer periphery of the supporting plate 60 with the outer edge of the insert 70 extending radially outward beyond the outer wall of the plate 60 and with the outer wall of the body portion 68 in substantial alignposed position relative to the segmental cutter elements 62 with the tapered lugs 80 in engagement with the tapered slots 74. The plate 64 is engaged by the machine bolts 66 and upon tightening of the bolts 66 is moved axially inward toward the plate 60 thereby irmly to secure the plurality of elements 62 in the desired position by means of the wedging action produced by the cooperating slots 74 and lugs 80.

If itis desired to remove a particular one of the cutter elements 62, the machine bolts 66 are rotated to loosen the clamping plate 64. Thereupon, the operator may remove the desired elements 62 by moving the selected elements upwardly to disengage the interlocked shoulders 76 and 78 and then by sliding them radially outward. The new or reconditioned element 62 is replaced on the plate 60 and secured in a desired interlocking position in the manner described above.

The third embodiment of the invention shown in Figs. l2 to 15, inclusive, of the drawings comprises a milling cutter indicated generally as having a circular supporting plate 92 upon which are detachably supported a plurality of individual cutting elements 94. The elements 94 are secured in a desired position by means of a clamping plate 96 provided with a plurality of tapered fingers 98 at the outer edge thereof. The fingers 98 are not only tapered inwardly and downwardly at the sides thereof but also inwardly from the outer extremity of these fingers. p

To support the plurality of cutting elements 94 in a quickly detachable manner on the milling cutter 90, the supporting plate 92 is provided with a plurality of upstanding lands or lugs 100 which are positioned adjacent the outer edge thereof and spaced from each other. The plurality of cutting elements 94 which are formed with outwardly and downwardly extending sides 102 (Fig. 14) are positioned upon the plurality of lugs 100 with the cutting edges 104 thereof extending outwardly beyond the periphery of the plates 92 and 90. The clamping plate 96 is then superimposed upon the plate 92 in such a position that the tapered fingers 98 are interposed between adjacent cutter elements 94. The plate 96 is then moved toward the plate 92 and secured in position thereupon by a plurality of machine bolts 103 so that the tapered walls of the lingers 98 wedgingly engage the tapered walls 102 of the cutter elements 94.

It is possible to secure a very tight engagement between the cutter elements 94, the clamping plate 96, and the supporting plate 92 by virtue of the provision of the upstanding lands or lugs 100, since it is possible to move the clamping plate 96 and fingers 98 thereon beyond the lower edge of the cutting elements 94 and thereby produce an increased locking action. If the elements 94 were seated on the upper surface of the plate 92, it would be necessary to provide au increased spacing or pitch between the elements 94 since it would be necessary to provide tapered fingers 98 of greater width and consequent greater peripheral length.

To prevent vibratory destruction of the cutting edges 104, the plurality of cutter elements 94 (Fig. l5) are coated with a vibration damping or absorbing material 105 such as the Solectron material referred to above.

7 If it is desired to increase the vibration damping effect, both an upper surface 106 of thelands 100 and the tapered walls of the lingers 98 may also be coated with the vibration absorbing or damping material 105.

Because of the low pitch made possible by the narrow tapered fingers 98, it is possible to utilize or achieve a large amount of metal removal in terms of inches per minute by operating within the parameter conditions described in the above identilied See patent. Also by virtue of the low pitch between teeth and consequent high metal removal rate, it is possible to provide a milling head in accordance with this invention which is capable of being utilized with high horsepower sources of energy without the attendant disadvantage of undesirable large weights in the milling head.

In operation, the plurality of cutter elements 94, which are formed of a suitable material such asv carbide and which are previously formed with the desired removal angle and rake, are positioned on the upper surfaces 106 of the lands 100. Then, the clamping plate 96 is placed in a superimposed relationship with respect to the sup'- porting plate 92 with the plurality of tapered fingers 98 interposed between adjacent cutter elements 94. Thereupon, the clamping plate 96 is moved toward the plate 92 by securing means 103 so that the elements 94 are rigidly secured in position relative to the plate 92. The final grinding of the cutter elements 94 is preferablydone after assembly, to bring all of the cutter faces into the's'ame plane.

If it is desired to replace or recondition any or all of the plurality of cutting elements 94, the clamping platel 96 is loosened and the plurality of elements 94 are moved out of engagement with both the tapered fingers 98 and the supporting lands 100.

Although the cutter assemblies disclosed herein are shown as being of cylindrical shape, it will be appreciated that any desired configuration maybe employed. In cutters constructed in accordance with the presentinvention, the utilization of the vibration damping material and the novel securing means disclosed above makes it possible to provide cutting teeth which are spaced by a minimum pitch and which are secured in a substantially vibrationless yet quickly detachable relation so as to provide a milling head susceptible of use with the high speed milling techniques disclosed in the above identified patent.

While particular embodiments of the invention have been shown, it will be understood that-the invention is not limited thereto, since many modifications may be made, and it is therefor contemplated by the-appended` claims to cover any such modifications as fall within the true spirit and `scope of the invention.

detachably secured to and spaced from the supportingv member, a plurality of tapered fingers formed integral with said clamping means and projecting radially outward therefrom, a plurality of cutting elements interposed between the supporting member and the clamping means in engagement with the lugs and with the sides of the elements in engagement with the tapered fingers, and vibration damping means interposed between said ngers and said elements to prevent vibratory destruction of the cutting edges of elements. v

2. Al milling cutter comprising a supporting member adapted for rotation about an axis and including a plurality of peripherally spaced and axially extendingportions, a plurality of cutting elements positioned on said portions, clamping means carried on said supporting member and including a plurality of radially extending tapered fingers interposed between adjacent elements in engagement therewith, and means for moving said clampingmeans toward said supporting means along said axis to move the fingers into wedging engagement with the elements to secure them in position on said portions.

3. The cutter defined by claim 2 in which the tapered fingers extend into the spaces between the portions on the supporting member.

References Cited in the file of this patentI UNITED STATES PATENTS Article: New`High Speed Milling Technique from The Iron Age magazine, Feb. 14, 1946, pages'76 and 77.

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