US2367857A

US2367857A - Grinding wheel dressing

Info

Publication number: US2367857A
Application number: US470726A
Authority: US
Inventors: Jack H Findlater
Original assignee: Packard Motor Car Co
Current assignee: Packard Motor Car Co
Priority date: 1942-12-31
Filing date: 1942-12-31
Publication date: 1945-01-23
Anticipated expiration: 1962-01-23

Description

Jan. 23, 1945. J FINDLATER 2,367,857

GRINDING WHEEL DRESSING Filed Dec. 31, 1942 H5 5 INVENTOR.

UAQK H. ENDLATER BY% W Patcnied Jan. 1945 GRINDING WHEEL nan-same Jack H. Flndlater,

Packard Motor Car Company, a corporation of Michigan Detroit, Mich minor to- Detroit, Mich Application December 31,1942, Serial No. 470,726

3 Claims.

This invention relates to the dressing of grinding wheels and particularly to such dressing by the use of a diamond cutting tool.

The invention will be described in connection with a grinding wheel having a peripheral crosssection of V-shape, with the side facesof the v straight or in a right line, but the invention may be adapted to dressing wheels of other contours and is not intended to be limited to the specific form shown other than as indicated in the claims. Such a grinding wheel as is illustrated may be used for grinding threads, external or internal, but it may be used for other purposes and its cross-sectional form may be changed to. suit its particular purpose.

One of the purposes of grinding threads instead of cutting orrolling them is to obtain extreme accuracy, smoothness, and uniformity, and in the use of a grinding wheel for the purpose the wheel itself must be maintained so that its abrading surfaces are always in as nearly exact shape and relationship as it is possible to keep them. In practice, therefore, these abrading surfaces of the grinding wheel are dressed or renewed at frequent intervals to maintain this accuracy, and sometimes this dressing is done as aften as between every grinding operation.

Grinding wheel dressing of the character described is in practice most frequently accomplished with a diamond crystal set, in a holder to form a tool and this tool is mounted on a support and moved across the face of the grinding wheel as the latter is rapidly rotated on its axis. The diamond crystal is set with a 'sharp point extending from its holder and this sharp point is advanced to contact with the wheel face to be dressed. The tool is then moved across the face of the wheel.

For the particular type of grinding wheel dressing referred to herein, diamond crystals of octahedron shape are usually selected and most generally these diamonds are somewhat elongated so that their-two principal opposite points are farther apart than the greatest diameter at the middle. In using such a diamond about one-half of it is imbedded in the material of the holder so that one of the sharp points extends above the holder and when that point is worn down by use the diamond is removed from the holder and reversed so that the opposite point is uppermost and the worn point is imbedded in the material of the holder. Thus each octahedron diamond crystal has two working points and when both are dulled .the diamond is discarded or given over to other uses.

It is well known that diamonds of natural formation have a hard skin of appreciable thickness, which is doubtless the reason for selecting diamonds .of natural octahedron shape for wheel dressing such as above-described instead of using diamonds of other shapes and lapping them to a point. A diamond cut or lapped to shape has had its hard skin removed and consequently it will not wear as well as a natural diamond. Also, by selecting diamonds that are pointed in their natural state the cost involved in the lapping opereration is saved.

It is one of the objects of the present invention to greatly increase the diamond life in a grinding wheel dressing operation such asreferred to herein.

Another object of the invention is to greatly increase the number of useful cutting points on an octahedron diamond for use in dressing grinding wheels.

Another object of the invention is to provide a four-pointed diamond tool for dressing grindwhich the octahedron ural point lapped of! to form a four-point cuting machine is indicated at ing wheels and particularly the provision of such a tool in which the points are formed by the hardest portlon of the diamond.

Referring to the drawing,

Fig. 1 is a side view oi a portiorfof a grinding wheel and dresser embodying the invention;

Fig. 2 is a plan view of the grinding wheel and dressing tool;

Fig. 3 shows a dressing tool having the usual octahedron diamond; v

Fig. 4 shows a dressing tool of this invention in diamondhas had its natting tool;

Fig. 5 is a still greater enlarged view of the end of a dressing tool indicating how the diamond may be lapped to provide the multiple cutting points.

Fig. 6 shows a diamond that has been lapped off at both ends; and

Fig. '7 is an end view of a diamond showing the four cutting points.

For better illustration the diamond in each of the figures referred to is considerably enlarged.

In the drawing the grinding wheel of the dress- W, the dressing tool is marked T, and the diamond is marked D. No attempt has been made to hold these parts to proper relative sizes because to make the diamond as small as it is used in practice would 4 make it extremely difllcult to illustrate. Thus, the grinding wheel may be three or four inches or a foot in diameter, depending upon the character of work it is to do, and usually the diamond is no more than one-half carat and probably does not extend above the surface of its holder more than a sixteenth of an inch.

The grinding wheel W is mounted on a suitable part of the machine at H or other suitable means. The sectional form of its cutting periphery is shown in cross section at l2 in Fig. 1 and in plan at IS in Fig. 2. As shown, the cutting part of the wheel is V-shapecl with straight side faces l4 and the shape of the side faces determines the shape of the thread to be out. As the point of the V is worn the wheel must be dressed to reshape the point, and this is done by passing a diamond dressing tool across the face of the wheel in a plane parallel with or tangent to that face. There are usually two of these tools working in unison, one on either side of the wheel, but for the purpose of illustrating ,the invention only one such dressing tool is shown. It will be understood that a similar tool may simultaneously traverse the face M of the wheel on the other side thereof.

A means for moving the dressing tool across the face of the wheel and parallel thereto is shown in Fig. 1, this means comprising a frame having a slide 2| upon which slides a support 22 for the cylindrical tool T, adjustably held therein by the bolt 34. Said support is moved along the sliding surface by an arm 23 suitably operated by the machine. The slide 2| is arranged at the correct angle to move the tool in the desired plane relative to the face ll of the grinding wheel. In Fig.2 this plane of movement is indicated by the broken line X.

In Fig. 3 there is shown the conventional diamond tool comprising a holder 25 having a diamond D of octahedron shape imbedded in the softer metal 26 at the end of the holder. Approximately one-half of the diamond-extends above the metal of the holder, this portion of the diamond being of pyramidal shape and the lower half of the diamond be g shown in dotted lines indicating that the lower half also is of pyramidal shape, these two pyramids being base-to-bas'e and thereby forming the ordinary octahedral crystal. The sharp point 21 of the diamond is what is usually employed to trim the sides of a grinding wheel, and when that point is worn down until it is no longer useful, the diamond is removed from the holder, as by melting the soft metal 26, is then reversed in the holder so that the dull point is below the surface and the newer, sharpened point is exposed. The tool is then used until this second point of the diamond crystal is dull, and then the diamond is supposed to be of no further value for dressing purposes.

This applicant, however, has found that an octahedron diamond such as referred to above can be made to provide additional hard cutting points after the first cutting point has been dulled. This is accomplished by lapping off the point of the pyramid projecting from the holder so that a square, flat top 32 is formed on the diamond, as shown in Figs. 4, 6 and '7. This provides four points 30, one at each corner of the square, and each point, as shown within the circle 33, is formed by two hard natural sides 3| and one lapped face or top 32, But this lapped face 32 is edged by the natural skin of the diamond, indicated by the dotted line in Fig. 7, and this skin provides at each of the four points an appreciable depth of hard crystal so that all three sides of each point are formed by hard skinsurfaces, and since these four points are not as thin as the Ill and is driven by a beltoriginal four-sided point 21 there is more body behind the actual cutting part and consequently less vibration in operating on the grinding wheel. Indeed, it is found in practice that these threesided points have extremely good cutting and lasting qualities and when properly presented to the side face of a grinding. wheel they will dress the wheel with an even greater degree of accuracy than the original point 21.

In use, one of these points 30 is first presented to the side face of the grinding wheel for the dressing operation and used until dulled; then the diamond tool is turned approximately to present another of the points 36. Thus the tool may be turned successively to its four point positions and when all four points have been dulled with use, the diamond is removed and reversed and the pyramid of the other'end of the diamond is used as was the first half thereof. With this tool, instead of having only two useful cutting points each octahedron diamond has ten useful points, the original single point at each end and the four points at each end provided by lapping the diamond to form the squared flat top. A diamond that has had both ends lapped oil. is shown in Fig. 6.

Indeed, in some instances each pyramid end of the diamond may be lapped twice or more as shown in dotted lines in Fig. 5. Here the point 2'! may be used until dulled, then the diamond may be lapped to a flat top as shown in dotted lines at 28, and after the four points of that square have been dulled the diamond may be again lapped to present a four-point square as shown by the dotted lines 29 in Fig. 5. Thus, that pyramid half of the diamond has provided nine useful cutting points before the diamond is reversed in the holder. The number of times the diamond can be lapped oif depends, of course, very largely upon the size and shape of the crystal itself. In practice some diamonds have been lapped off as many as four times on one end, thus providing seventeen dressing points instead of one.

In Figs. 1 and 2 is shown the position of the diamond tool with relation to the grinding wheel. The-four points 30 of the tool may be consecutively presented to the face of the grinding wheel by merely turning the tool T 90 on its axis and the wheel in this instance being mounted on a horizontal axis for rotation in a vertical plane. The term horizontal and vertical are used in the specification and claims to illustrate the relative positions of the parts.

As shown, the axis of the tool T is set at an angle of about 45 from the plane of rotation of the grinding wheel, and with a grinding wheel pointed 55 the angle between the face thereof and the axis of the tool will be 72%. Also, the tool is arranged in its support so that two of the side edges of the diamond are in a horizontal Thus the two side faces of the diamond nearest the face of the grinding wheel will form two of the three. sides of the cutting point and these two sides are the natural hard sides of the diamond crystal and consequently give the cutting point maximum hardness.

While I have herein described in some detail a specific embodiment of my invention, which I deem to be new and advantageous and may specifically claim, I do not desire it to be understood that my invention is limited to the exact details of theconstruction, as it will be apparent that changes may be madetherein without departing from the spirit or scope of my invention.

What is claimed is:

1. A wheel dressing diamond comprising a crystal having a portion thereof of pyramid shape with the point removed leaving a flat face forming a plurality of cutting points the side faces of the pyramid having natural skin surfaces.

2. A wheel dressing diamond comprising a crystal, a portion of which is of rectangular pyramid shape with the point of the pyramid removed leaving a square face normal to the major axis of the crystal and forming cutting points, each cutting point having three sides and formed for an appreciable depth of the hard natural skin of the crystal.

3. A wheel dressing diamond comprising a diamond having a portion thereof of rectangular pyramid shape with the point of the pyramid removed leaving a square flat face forming four cutting points, the four side faces of the pyramid having natural skin surfaces.

JACK H. FINDLA'I'ER;