US2425859A

US2425859A - Cutter grinder

Info

Publication number: US2425859A
Application number: US539741A
Authority: US
Inventors: Oscar M Braaten
Original assignee: Cincinnati Milling Machine Co
Current assignee: Milacron Inc
Priority date: 1944-06-10
Filing date: 1944-06-10
Publication date: 1947-08-19
Anticipated expiration: 1964-08-19

Description

Aug. 19, 1947. V o. M. BRAATEN 2,425,859

. CUTTER GRINDER' I Filed June 10, 1944 v s Sheets-Shet 1 Ef INVENTOR. 5

' ATTO/P/YEY Aug. 19, 1947.

o. M. BRAATEN 2,425,859

CUTTER GRINDER s Sheets-Sheet s JNVENTOR. im" Chea /7394a? A TTOP/YEX Patented Aug. 19, 1947 CUTTER GRINDER Oscar M. Braaten,

The Cincinnati Rock Island, 111., assignor to Milling Machine 00., Cincinnati, Ohio, a corporation of Ohio Application June 10, 1944, Serial No. 539,741

14 Claims.

This invention relates to grinding machines and more particularly to improvements in cutter grinders.

One of the objects of this invention is to provide an improved and efficient cutter grinder,

Another object of this invention is to provide an improved cutter grinder for sharpening contour helical cutters.

Another object of this invention is to provide an improved cutter grinder for sharpening contour helical cutters which may be set up to cause a grinding wheel to automatically follow the ,cutting edge of a contoured helical tooth and grinding a substantially constant clearance angle at said edge regardless of the angle of the tooth or the variations in the contour of the cutter.

A further object of t s invention is to provide an improved cutter grinder for sharpening contour helical cutters in which each tooth may be accurately ground with a substantially constant clearance angle throughout its length and in a single continuous pass between the grinding wheel and th tooth.

An additional object of this invention is to provide an improved machine for grinding contour helical cutters which has separate adjustable or change devices for generating selective helices, for controlling the contour of the helix by varyin the radius thereof, for determining the clearance angle for shifting the phase of the helix whenever compensations for the rake angle of the tooth become necessary.

Other objects and advantages of the present intural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

Referring to the drawings in which like reference numerals indicate like or similar parts:

Figure 1 is an elevational View of a mechanism embodying the principles of this invention.

Figure 2 is a section on line 2-2 of Figure 1.

Figure 3 is a plan view of the mechanism shown in Figure 2.

Figure 4 is a detail section on the line 64 of Figure l. a

Figure 5 is an end elevation as viewed on the line 5-5 of Figure 1.

Figure 6 is a diagrammatic view of a cutter tooth showing the relationship of the various angles.

Figure 7 is a diagram illustrating phase shifting of a generated helix.

This invention relates to improvements in a cutter grinder of the type disclosed in my copending application, Serial No. 449,311, which was filed July 1, 1942, and which issued as Patent No. 2,419,529, April 29, 1947.

In the machine shown in said cO-pending application it is necessary to use a duplicate cutter of the type to be ground, or a control cam having a tooth formed thereon similar to the tooth of the cutter to be ground as a model to control relative rotative movement between cutter and grinding wheel, which means that in the cas of spiral toothed cutters the model must have the same spiral and the same tooth rake angle as the cutter to be sharpened. Due to the large number of possible spirals and the larger number of possible rake angles, the resulting number of dilferent combinations of these two becomes so large as to to stock a set of change cams for the machine if the full usefulness of the machine is to be obtained.

By means of this invention separate devices are provided for determining the helix to be generated and the rake angle to be compensated for so that a greater number of combinations can be obtained with less mechanism. Thus the machine of this invention may be preset for grinding a contour helical cutter by the use of a first selective means for determining the clearance angle to be ground at the cutting edg of the cutter, a second selective means for determining the lead angle of the helix to be generated, a third selective means for determining and controlling the radius of the generated helix during its generation and thereby make the generated helix conform to the shape or contour of the cutter to be sharpened, and a fourth selective means which may be preset in accordance with the rake angle of the cutter tooth which is effective during in or out movement of the grinding wheel to effect a phase hift of the generated helix to correct or compensate for errors which might otherwise be introduced to vary the clearance angle whereby a cutter tooth may be ground in a single continuous pass of the grinding wheel relative to the tooth.

The basic structural features of the machine shown herein conform in general to the machine shown in the aforesaid copending application and comprise a bed or frame I 6 having guideways H as shown in Figure 3 for slidably supporting a traversable slide I2 upon which is superimposed a cross slide I 3 which, in turn, supports a turntable I4 that carries a grinding wheel I 5 rotat- S mounted thereon. rotation E of the grinding wheel passes through ably The central plane of the axis lb of the turntable whereby the plane of rotation of the grinding wheel may be swiveled about the axis of the turntable.

A headstock i6 is mounted upon the bed or support It for supporting a rotatable spindle ll to one end of which is attached an arbor it for supporting a work piece which is a cutter, such as it, the teeth of which are to be ground or sharpened by the grinding wheel in. The cutter is frictionally secured and clamped to the arbor by means of locking nut 294 which is threaded on the end of the arbor. This makes it possible to use various sizes of arbors depending upon size of the bore of the cutter.

The parts are set up for a grinding or sharpening operation by rotatably positioning the cutter I9 on the arbor it until a cutting edge such as 23 is positioned in a horizontal plane 21 passing through the axis of the cutter. This positioning of the cutting edge is facilitated by a gage memer 2:3 which is mounted on the side of the headstock as shown in Figure 1 for longitudinal sliding movement on a supporting bracket 25. The gage may be clamped by a clamp screw 25, it being understood that the gage has a longitudinally extending slot formed therein whereby the gage may be moved into or out of engagement with the cutter. After these adjustments have been made the cutter is secured to the arbor by lock nut 2G. The grinding wheel is then raised or lowered by adjusting screw 2% with respect to the plane ii a predetermined amount, as for instance by the amount indicated by the reference numeral 21 in Figure 2 to grind the necessary clearance angle on the margin of the cutter tooth adjacent to the cutting edge. This adjustment is in accordance with standardized practice and the further off center the greater the clearance angle will be.

For a better understanding of this invention and the problems involved, reference may now be had to Figure 6 which shows a conventional cutter tooth, the tooth itself being indicated generally by the reference numeral 23. These teeth are formed by cutting longitudinally extending slots or gullets 29 in the periphery of the cutter body and the shape of this gullet is such as to form the cutter face 30. The tooth also has a cutting edge 23, a margin 3| and a secondary clearance or relief 32 on the back of the tooth. The gullet may be cut in such a manner that the tooth face 3%! lies in the radial plane 33, in which case the face is said to be radial, or it may be at an angle to this plane in which case it has a positive or a negative rake angle. The face 39, for instance, is shown as having a positive rake angle, the value of which is indicated at 36 1. but if the tooth face fell on the line, identified by the reference numeral 3d, it would have a negative rake angle, the value of which is indicated at Ma. The margin is the surface to be ground in order to sharpen the cutter and to give it clearance at the same time. The angle which this margin makes with a tangent S5 to the cutter constitutes the clearance angle which is identified by the reference numeral 3-5.

In a cutter having a helical cutting edge, the helix of this edge may be generated mathematically by revolving a straight radial line about the axis of a cutter in screw-like fashion so that as it revolves it also moves axially. This means that each radial element of the surface produced is a straight line. Thus a control cam may be generated in the same manner and since each element of the generated surface is a straight line a cam follower utilized therewith may move radially in or out with respect to the cam axis without causing rotation of the cam, but movement of the follower parallel to the cam axis regardless of its radial distance therefrom will cause rotation of the cam will produce the same angular rotation regardless of its radial distance from the cam axis. The distance that the, line moves along the axis of the cam during one rotation about the cam axis may be desig nated as the lead and corresponds to the lead of the helix.

In view of this latter fact, it is not necessary to make the control cam the same diameter the cutter with the result that the diameter of the cams may be standardized but still each cam will cover all diameters of cutters having the same helix. The radius of the cam, however, should be made great enough to take care of the maximum depth of gullet which would represent the maximum movement of the grinding wheel in moving from the periphery of the cutter to the bottom of the gullet.

The change helix cams, such as the one indicated by the reference numeral 3'? in Fig. l, are generated in this manner and this method results in a saving in the number of cams and also a saving in the expensive material of which the cams are made.

As shown in Figure l, the cams are mounted on an arbor 553 which projects from the opposite end of the headstock from the cutter arbor and is secured to the spindle ill for controlling rotation of the cutter, or in other words, generation of a helical grinding path corresponding to the helix of the cutting edge being ground. The cam is frictionally secured to the arbor by a loci: nut 39 threaded on the end of the arbor in a similar manner utilized for clamping the cutter. In order to control rotation of the cam in accordance with longitudinal movement of the grinding wheel and in timed relation therewith so that the cutting edge is always in proper position with respect to the grinding wheel, a follower [i3 provided for engagement with the generated or control surface of the cam and since it is neces sary that this follower partake of both directions of movement of the grinding wheel it is carried by a bracket H, Figure 1, which is attached to the cross slide l3. Thus, the bracket moves in and out with the cross slide 13 and longitudinally with the traversing slide l2.

The grinding wheel is-caused to follow the contour of the cutter by means of a contour controlling cam l2 which has the same contour as the cutter to be sharpened and which is removable and interchangeable with other cams and is attached to a cross adjustable slide 53 by means of clamping screw and nut M. The slide 53 is adjustable on the main frame ill to take care of variations in the diameter of cutters being ground, it being necessary that the edge of the cam 42 be in vertical alignment with the cutting edge of the cutter as shown in Figure 2. The turn table M carries a follower pin dB for the cam t2 which is also interchangeable and which is of a radius equal to the smallest radius in the contoured outline of the cutter. The grinding wheel i5 is also chosen of such width that the periphery thereof may be trued to a radius equal to the radius of the pin 55. The grinding wheel is positioned so that the center of its semi-circular face is in verticalalignment with the centhat if the the slide 13 follower iii were rigidly attached to that this in or out movement will not accordance with edge must always lie in the face of the tooth. This would 39 ing Wheel i5 moves from the large diametric portion 46 of the cutter shown in Figure 1 to the smaller diametric portion 41, corresponding to distance 4'! for instance in Figure 6, the cutting may be adjusted transversely to the direction of he support 55. The support 55 adjustment of i is mounted in a T-slot guideway 56 of a bracket diameter take of the in and out and transverse movements of the grinding wheel.

The plane 5 la which contains the center of the pin 5! and is tangent to the ends of the followers, also passes through the center 59 about which the template 53 is angularly adjusted and this plane is co-incident with the radial plane 33 of Figure 6 or the radial plane 2| of Figure 2 in which the cutting edge of the cutter lies.

larged head to from which projects an integral round stud 6!. This stud passes through a bore 52 in an adjustable cross slide 63 and also an elongated slot 64 formed in an upstanding brackthis rotational adjustment is independent of the cross slide 33. The angle of adjustment may be determined by graduations 69 formed on the head 60 in conjunction with a zero mark 'HJ carried by the cross slide. It can he mathematically determined what the angle of adjustment of the template should be for each different rake angle, but in practice a simpler method is used. The operator when setting up the machine moves the grinding wheel which is stopped at this time into engagement with a tooth on the smallest diameter of the cutter with the point of contact lying in a plane connecting the centers of the wheel and cutter.

various supports so that the center 59 engages the follower till. The grinding wheel is then moved out and into engagement with the control cam will occur.

It should he noted that the total resultant rotation of the cam which is produced at this time is the resultant of two independent actions or in other words is composed of two independent components. The first component is the rotation due solely to the helix, and the second, rotation due to the rake angle. Since the lead of the helix of the cam is the same as the helix of the cutting edge, the rotational component due to the helix will not cause any displacement up or down of the follower 8. The second rotational component, however, will cause displacement of the follower id and thus of follower The template is then angularly adjusted into contact with follower till and clamped.

It will now be evident from Figure 5 that movement of the followers Qt and iii to the right or left-which would correspond to in or out movement or" the grinding wheel with. respect to the cutter will cause rotation of the cam 32* either clockwise or counterclockwise as the case may be and thereby impart a deviation or shift of the helical grinding path being generated between the cutter and grinding wheel. This deviation corresponds to a phase shift of the helix. This is bestrepresented by a diagr'amsuch-as shown'in Figure '7 in which axial. movement of the generatrix is plotted against rotation. Uniform movement in both directions produces the straight line H which represents the helix A direct in or out movement of the grinding wheel unaccompanied by any traversing movement will cause a rotation only which is represented by the line 12. If the grinding ,wheel then traverses on a constant diameter of the cutter the helix picks up again and is represented by-the line 13. The helix has, therefore, experienced a phase shift to the left by the amount indicated at M. Thus, in or out movement of-the grinding wheel efiects a phase shift of the'initial helix.

Attention is invited to the fact that the frictional urge imparted by the grinding wheel on the cutter during grinding is such as to-produce a clockwise urge on the cutter and thereby on the cam 3! as shown in Figure 5 which reacts through the followers and the lever 49 to maintain the follower 50 in contact with the template Es. Thus, by rotating the grinding-wheel $5 in a counterclockwise direction all lost motion is taken up in the various connections.

After one tooth of the cutter-has been ground the locking nut 26 is loosened, the cutter rotated one tooth which is brought into alignment with gage 24, and the cutter secured again to its arbor by the lock nut 20. By this means the cutter may be indexed relative to its control cam and thus the one control surface on the cam will suffice for all teeth of the cutter. It will'be noted that after the template 53 has been adjusted to the proper angle to compensate for the rake angle of the tooth that in and out movement of the grinding wheel will cause movement of the follower 59 relative to the plate 53 and thereby rotation of the lever arm 69 and follower 4i) imparting rotation to the cam 3?, to compensate for the rake angle of the cutter and maintain the cutting edge thereof always in the plane 33 and thus the proper clearance angle on the margin 3!.

There has thus been provided an improved cutter grinder which is especially adapted for grinding helical contour cutters and which by use of very simplified means is adapted to accurately maintain the proper angular relationship between the cutting edge of the cutter and the grinding wheel and thus the proper clearance angle during transverse or crosswise movements of the grinding wheel and regardless of the helical lead, the diameter of the cutter, or the shape of the contour.

What is claimed is:

1. In a cutter grinder having a rotatable work support and a grinding wheel support mounted for two-directional relative bodily movement in a plane parallel to the axis of the work support, co-acting means between the supports for imparting rotation to the work support during relative bodily movement between the supports in a path parallel to the axis of the work support and other co-acting means, effective upon departure from said parallel path to impart an additional component or rotative movement to the work support.

2. In a cutter grinder, a work support, a grinding wheel support mounted for two-directional movement relative to the work support, co-acting means responsive to movement in one direction for causing rotation of the work support and other co-acting means responsive to movement transversely of the first-named movement for imparting an additional component of rotation to the work support either in the same or opposite direction to the first-named rotation.

3. In a cutter grinder for sharpening helical contour cutter teeth formed with a rake angle and having a cutter support, a grinding wheel support and a rotatable grinding wheel mounted thereon, the combination of coacting means for maintaining the cutting edge of the cutter teeth in predetermined relation with the periphery of the grinding wheel during relative bodily movement of the wheel including a first cam means between the supports for determining the contour of the cutter, a second cam means for controlling rotation of the cutter and thereby the lead of the helix and a third cam means coacting with the second cam means for imparting a corrective movement to the second cam means in accordance with the rake angle.

4. In a cutter grinder having a main support, a work supporting spindle jcurnaled in the main support, a grinding wheel support having a grinding wheel mounted thereon, said grinding wheel support being guided for two-directional movement relative to the work supporting spindle, the combination of means to secure a spiral cutter to said spindle, a cam operatively connected to said spindle, a follower carried by the grinding wheel support for engagement with said cam for controlling rotar movement of said spindle dur ing traversing of the grindin wheel support, and additional means carried by the main support and coacting with said follower for imparting corrective movements to the first-named cam during traversing of the grinding wheel.

5. In a cutter grinder having a rotatable work supporting spindle. a grinding wheel, a support for said grinding wheel movable in two directions relative to said spindle, the combination of a profile cam mounted on the main support and coacting with the grinding Wheel support for causing the grinding wheel to follow the contour of a cutter being ground, a helical cam having a straight line radial element, a follower therefor carried by the grinding wheel support for imparting rotary movement to the Work spindle during traversing of the cutter, additional cam means carried by the main support and operativei connected to the follower for phase shifting the helical movement in accordance with the rake angle of the grinding wheel during radial movement thereof with respect to the work spindle.

6. In a cutter grinder for sharpening helical contour cutters, the combination with a cutter support and a grinding wheel support relatively movable in two directions, a contour cam carried by one of said supports, a follower carried by the other support coacting with the profile cam, a helix determining cam operatively connected for rotation of the cutter, a follower for said cam and operatively connected with the grinding wheel support, and additional cam means carried by the main support and coacting with said follower for imparting rake angle compensations to the helical cam during relative radial movement between said supports caused by the contour earn.

'7. In a cutter grinder having a rotable spindle for supporting a cutter to be sharpened, a grinding wheel, means to support said grinding wheel for two-directional movement relative to said spindle, a helical control cam attached to said spindle, each element of said cam being a straight radial line perpendicular to the axis thereof, a follower for said cam operatively connected to the grinding wheel support whereby radial movement of the grinding wheel with respect to the cutter will not effect rotation of the cam but traversing movement will effect rotation of the cam, and means to effect a corrective positioning of the follower during radial movement of the grinding wheel.

8. In a cutter grinder having a work supporting spindle and a grinding wheel supported for twodirectional movement relative to the spindle, the combination of cam means carried by the spindle and a follower carried by the grinding wheel support for causing rotation of the spindle in timed relation to the longitudinal movement of the grinding wheel support, means to pivotally support the follower on the grinding wheel support, and a relatively fixed sine bar ooacting with the pivoted follower for imparting compensatory movements thereto in accordance with the rake angle of the cutter being sharpened during radial movement of the grinding wheel relative to said spindle.

9. In a cutter grinder having a work supporting spindle, means for attaching helical contour cutters to said spindle, a grinding Wheel supported for two-directional movement relative to said spindle, cam means attached to said spindle for imparting rotary movement to the cutter during longitudinal movement of the grinding wheel, a pivoted lever carried by the grinding wheel support, followers attached to opposite ends of the lever, one of which coacts with said cam, additional cam means ooacting with the other follower for imparting movement to the cam during radial movement of the grinding wheel with respect to the spindle.

10. In a cutter grinder having a work supporting spindle, means for attaching helical contour cutters to said spindle, a grinding wheel supported for two-directional movement relative to said spindle, cam means attached to said spindle for imparting rotary movement to the cutter during longitudinal movement of the grinding wheel, a pivoted lever carried by the grinding wheel support, followers attached to opposite ends of the lever, one of which coacts with said cam, additional cam means ooacting with the other follower for imparting movement to the cam during radial movement of the grinding wheel with respect to the spindle, the arms of said lever being of equal length and said pivot being mounted parallel to the axis of the spindle.

11. In a cutter grinder having a main support, a work supporting spindle journaled therein, a

predetermined radial plane during radial or traversing movements of the grinding wheel to insure the formation of a constant clearance angle at the cutting edge regardless of changes in the contour of the cutter or the spiral angle of the cutting edge.

12. In a cutter grinder having a work supporting spindle, a grinding wheel and means for supporting the grinding wheel for two-directional relative movement with respect to said spindle, the combination with a cam on said spindle and a follower carried by the grinding wheel support for causing rotary movement of the spindle during traversing of the grinding wheel, a relatively fixed sine bar, means to adjust the angular relation thereof with respect to a radius of said cam, a follower for said sine bar and operatively connected to the first-named follower for varying the position of the latter during radial movement of the grinding wheel with respect to the work supporting spindle.

two directional movement relative to said spindle for sharpening the cutting edge of a helical contour cutter attached to said spindle, the combination of a first means to cause rotation of the spindle and cutter in timed relation With traversthe grinding wheel, and other means for imparting an additional rotation to the spindle in the same or opposite direction during uniform movement of the grinding wheel toward or from the axis of the cutter.

14. In a machine for grinding the clearance angle at the cutting edge of a spiral contour cutter, the combination of a grinding wheel having an arcuate grinding face, means to relatively for relative traverse and lateral movements, means interconnecting said supporting means for imparting rotation to the cutter in response to either direction of movement, means for controlling the extent of said lateral movement and thereby the contour of said cutter, and means for supporting the grinding wheel for oscillation about an axis perpendicular to said radial plane and passing through the center of curvature of the periphery of the grinding wheel.

OSCAR M. BRAATEN.

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

UNITED STATES PATENTS Number Name Date 2,344,323 Pelphrey Mar. 14, 1944 1,689,135 Hanson Oct. 23, 1928 1,314,154 Scrivenor Aug. 26, 1919 1,443,640 Muller et a1 Jan. 30, 1923 1,472,827 Erdman Nov. 6, 1923 1,616,056 Mensforth et al Feb. 1, 1927 2,321,102 Pelphrey June 8, 1943 1,196,420 Barnes Aug. 29, 1916