US 2194546 A
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March 26, 1940. L. W. GOD DU ET Al.
DIAMOND LAP Filed Nov. 4, 1937 2 Sheets-Sheet l w H A Flam P151? FIZZ H NTOR WE/GHTON GODDU SZg ZL ATTORNEY FIB.
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LLOYD w BY Wei/211% March 26, 1940. L. w. GODDU ET AL 2,194,546
numoun LAP Filed'Nov. 4, 1931' 2 Sheets-Sheet 2 FIE. II FIE. I
FIEJI Ham INVENTOR WILL/0M J. WIEIGHTON LLOYD W GODDU I mond'particles in the wiremesh;
Patented Mar. 26, 1940 UNITED STATES.
DIAMOND LAP Lloyd W. Goddu and William :1. Wrighton,
I Southbridge, Mass, assignors' to American ptical Company, Southbridge, Mass, a voluu-y tary association of Massachusetts Application November 4, 937, Serial No.1'l2,800 3 Claims; (Cl. 51-278) This invention relates to diamond laps and to a method for making the same.
.An object of the inventionis to improve the wearing qualities of the diamond laps thus produced. I
In the accompanying drawings which illustrate our invention Fig. I is a perspective view of a diamond lap; Fig. II is a plan view of sheet metal carryin the diamond particles;
Fig. III is an end view illustrating the assembly of such a sheet with a core;
hating of" wire mesh with diamond particles;
.Fig.-VI is a detail sectional view on-an .enlarged scaleillustrating the fixing of the dia- Fig. VII is a diagrammatic sectional view illustrating the insertion of the diamond impregnated mesh in the lap;,'
, Fig. vm isf'a view similar. to'Fig. IV illustrat- I ing the insertion of adiamond carrying mixture' into the lap;
' Fig. IX is a plan view of wire mesh impregna'ted with diamond particles; Fig. X is a plan view of a lap having a plurala ity of layers of diamond impregnated meshset into the body of the lap;
Fig. XI is a sectional view on the line XI-XI of Fig. X;
Fig. XII is a plan view of a lap having diamond 35 impregnated mesh applied as a surface layer thereon; and
Fig. XIII -is a sectional view on the' line XIIL-XIII of Fig. XII.
In abrading devices such as laps which em- 40 ploy diamond particles as the, cutting agent to I do the abrading, the diamond particles are held or embedded in a material which gradually wears down as abrading proceeds. For the sake of economy the diamond particles should be firmly In accordance with our invention, we seembed the diamond particles-that as the matrix in which they are embedded gradually wears down they are all held, from first to last, with substantially the same degree of tenacity. This 5 means that a diamond particle of the samjesize Rockwell, which is the range Lof-hardness generally found suitable for diamond laps.
and sharpness: is maintained in operative position for substantiallythe same length of time, no matter whether thisparticleis reached towards the beginning or towards the end of the life of the abrading' tool as a whole. Q In Fig. I, wehave conventionally illustrated a diamond lap such as employed for grinding glass to a predetermined spherical surface. The body Ill ofthe lap is generally of copper or steel which is soft enough to wear down as the dia- I.
mlond particles'become used up, but is durable v enoughto provide a suitable mounting for the Fig. IV is a diagrammatic sectional view'illustrating the-insertionoff the diamond carrying .15 metal into the body of the lap;
Fig. V is a plan view illustrating the impregparticles so long as their useful cutting-life lasts. Inaccordance with our invention'we' form a multiplicity'ofdepressions in the body l0, then :0
insert abrasive carrying metalin these depressions and soften-.the inserted metal by heating,
in this way settlingutheiinserted metal into the depressions to form an integral part of the lap.
In the particular embodiment of our inven- '9 tion illustrated "in Figs,- II, III and IV, we use sheet copper for carrying the diamond particles.
Fig. II is a plan view showing the diamond particles which have been caused in any suitable fashion to adhere to the face of the sheet cop- 3| per. ii.
'We then fold the diamond carrying sheet of copper I I' about the core i2 of soft iron. This core is selected in suitable dimensions for wedging the sheet H in one of a multiplicity of kerfs 39 I4 formed in the lap l0 as diagrammatically illustrated in Fig. IV. It will be noted that the diamond particles are not dislodged from the sheet copper I'l during the inserting step because the particles are firmly held between the copperv and the soft iron core.
The kerfs are thus charged with the abrasive carrying metal; and the kerfs are preferably evenly distributed about the body of the lap so as to give a uniform grinding action. The lap is then heat treated under reducing conditions and raised to a temperature sufiiciently high to soften or melt the 1 copper. It is desirable to carry on this heat treatment in a reducing atmosphere, butreducing conditions can be ob- 5 tained in other waysif found more desirable. The whole'is then quenched. from about 1500 to 1600 F. to give the steel temper. The latter is then drawn to about 25 to 40 on the C. ,scale,
treatment hardens the steel suiiiciently so that it does notwear down rapidly enough to release the diamond particles before their useful life is finished. The diamond particles are emdiamond particles may be brushed over wire wesh l6, preferably of alloysteel wire which will resist softening at the temperature used for softening the copper. We select the mesh l6 according to the size of the diamond particles, for instance,
100 mesh. When the diamond particles are brushed over the wire mesh, each of the interstices receives a diamond particle so that these particles are quite uniformly distributed.
We find it advantageous to deposit a flash coating of copper over the alloy steel wire before the diamond particles are distributed in the interstices. We then plate the diamond impregnated wire mesh with copper l'l, so as to fix the diamond particles in-the wire mesh in the manner illustrated in Fig. VI. The abrasive carrying mesh I6 is protected on one or both sides with sheet copper l8, then folded together in a-plurality of layers to make up an insert l9, which is pushed intoa kerf M in the manner indicated in Fig. VII.
The lap is then heat treated under reducing conditions to melt or soften the copper, as set forth in connection with the first embodiment of our invention. Here the wire mesh serves to hold the diamond particles from rising to the surface and thus becoming segregated, while the copper is in softened condition; and therefore the diamond abrasive is uniformly distributed through-.
out the kerf l4. When the copper hardens again the particles are embedded in a matrix which tenaciously holds the diamond particles as the lap is gradually worn away to expose the underlying particles of abrasive. The lap is quenched and drawn in the manner set forth in connection with the first embodiment of the invention, to control the rate at which the lap wears away.
Fig. VIII illustrates a further modification of our invention in accordance with which a mixture of diamond dust and copper or brass particles or chips is forced into each kerf 14. If a brass is used, we prefer to use a brazing brass. After the copper and diamond particles or brass and diamond particles have been carefully mixed, the mixture is forced into the kerfs H. The lap is then heat treatedunder reducing conditions to sinter the particles of metal together. In this sintering operation the diamond carrying metal becomes moulded to the contour of the recess ll in which the metal is received. The body III of steel is then quenched and drawn in the manner set forth in connection with the first embodiment of our invention. 9
Control of the heat treating temperature so as not to render the copper or brass liquid, but rather to sinter the metal particles together. makes it impossible for the diamond particles to segregate out of the metal during the heat treatment.
A further modification of our invention is illustrated in Figs. IX, X and XI; and here the body Illa of the lap is provided with an annular groove 22 for receiving a plurality of layers of diamond impregnated mesh. One of the inserts 23 of diamond impregnated wire mesh is shown in Fig. IX. We prefer to impregnate the wire mesh with the diamond particles and secure the particles in place by the aid of electrolytically deposited copper as described in connection with Figs. V and VI of the drawings. Here the wire mesh is in the shape of an annulus which is of such size as to fit into the groove 22. The successive layers of in a depression, groove, or the like, as set forth in connection with Figs. VII, and XI, we may apply the impregnated wire mesh to the surface of the lap which is used in abrading. Figs. XII and XIII illustrate this modification of our invention.
The diamond impregnated wire mesh is prepared as set forth in connection with Figs. V, VI and VII. The wire mesh is in the shape of an annulus and is applied to the rounded annular shoulder or rim 26 of the lap as illustrated in Fig. XIII. The edges of the annulus are pressed down so that the wire mesh conforms to the contour of the shoulder and lies snugly against the surface thereof. The lap is then heat treated under reducing conditions to melt or soften the copper as set forth in connection withthe preceding embodiments of our invention. As copper diffuses into steel below the softening point of the latter, an excellent bond is thus efi'ected between the'diamond impregnated wire mesh and the steel lap. This results in a surface layer of abrasive in which the diamond particles are embedded in copper, the latter being reinforced by steel wire mesh. Inasmuch as the diamond particles are disposed in the interstices of the wire mesh, the diamond particles are each in efiect provided with a setting or mounting which affords ample support during the abrading operation until the useful life of the diamond particles is spent.
This latter is an important advantage from the point of view of economy. We have discovered that even with a matrix material which is particularly well adapted for retaining the diamond particles during grinding, the particles are inefficiently held if two or more of them are held in a single pocket. In other words, the matrix or embedded material must completely surround each individual particle so that each has its own setting or pocket. The use of the wire mesh into which the diamond particles are brushed is particularly advantageous in insuring that the individual particles are spaced apart and each tenaciously held by its own setting.
The procedure taught herein insures remarkable uniformity in the cutting operation throughout the life of the abrading device, thus promoting economical use of the diamond particles.
While we have illustrated and described certain embodiments of our invention, it will be understood that the invention may be otherwise embodied and practiced within the scope of the fol lowing claims.
1. In a method of producing an abrading device, the steps conslsting in forming a slot in' the device, dispersing abrasive particles among layers of metal softe'nable at a lower temperature than said slotted device, inserting saidabrasive carrying layers of metal in a slot of said device, and softening the metal with heat after such insertion so as to cause it to conform more nearly to the cross section of said slot.
2. In a method of producing an abrading device, the steps consisting in forming a narrow depression in the device, folding sheet metal to include abrasive particles and form an insert,
placing said insert in the depression in said device, and softening the metal with heat after such insertion so as to cause it to conform substantial- 10 1y to the cross-section of said depression.
LLOYD W. GODDU.
WILLIAM J. WRIGHTON. 1o