US2802360A

US2802360A - Friability testing of grinding wheels

Info

Publication number: US2802360A
Application number: US431326A
Authority: US
Inventors: Urban B Tangeman; Iii Nelson Emmons
Original assignee: Sheffield Corp
Current assignee: Sheffield Corp
Priority date: 1954-05-21
Filing date: 1954-05-21
Publication date: 1957-08-13
Anticipated expiration: 1974-08-13

Description

1957 u. B. T ANGEMAN ETAL- 2,802,360

FRIABILITY TESTING OF GRINDING WHEELS Filed May 21, 1954 IN V EN TOR.

FRIABILITY TESTING on GRINDING WHEELS Urban B. Tangeman and Nelson Emmons III, Dayton, Ohio, assignors, by mesne assignments, to The Sheflield Corporation, a corporation of Delaware Application May 21, 1954, Serial No. 431,326

2 Claims. (Cl. 73-38) This invention relates to a method for gauging the uniformity of the friable characteristic of different portions of a grinding wheel or the like.

One object of the invention is to provide a method for gauging the relative friability of different portions of a grinding wheel or the like, in which a gauge head supplied with air from a regulated pressure source is applied successively to different portions of a grinding wheel so that air is passed into exactly the same area at the different portions tested. By comparing the rates of air flow at the different portions tested the manner in which the grinding wheel will react when formed by a crushing roll may be predetermined. It has been found that grinding wheels that give sufficiently large variations in air flow at different portions are wheels that will not be uniformly crushed by a crushing roll.

Other objects and advantages of the invention will be apparent from the following description, the appended claims, and the accompanying drawings.

In the drawings, in which the same reference characters have been applied to like parts in the several views;

Figure 1 illustrates the application of the particularly disclosed gauging head in carrying out the method of this invention to determine the relative friability of different portions of a grinding wheel,

Figure 2 illustrates in longitudinal central section a particular gauge head for use in carrying out the present method,

Figure 3 illustrates a fragment of the gauge head of Figure 2 shown in association with a portion of a grinding wheel in sealed interfitting relationship therewith.

Figure 4 illustrates the lower end of the gauge head, and

Figure 5 shows a flow gauging instrument that may be used in conjunction with the illustrated gauge head for carrying out the present invention.

While the method may be practiced by a variety of apparatuses, there is herein shown and will now be described one such apparatus and in following the description of the apparatus the utility and application of the method will also be more clearly disclosed.

In the crush dressing of a grinding wheel for grinding workpieces of a particular configuration a crushing roll is forced into the peripheral surface of a grinding wheel while the roll and wheel rotate at the same peripheral lpeed. It has been found that if the friability of the grinding wheel is not uniform the crushing roll will meet with less resistance at one portion of the wheel than another and the resulting wheel form will not be truly annular. The difiiculties involved in grinding with such an irregularly formed wheel will be apparent. There has been no satisfactory previous method for predetermining the uniformity of the crushing reaction on the grinding wheel.

In accordance with the present method the relative friability of different portions of the grinding wheel before it is crushed is determined with precision and without affecting the grinding wheel. In carrying out the present invention air from a controlled pressure source is passed atent 2,802,360 Patented Aug. 13, 1957 successively into different portions of the wheel and the resulting air flows compared or gauged by means of a suitably calibrated instrument to give an indication of the friability characteristic. The gauge head is applied in sealed relationship directly to the periphery or an active surface, or to the wheel sides near the periphery, and the resulting air flows that take place through the particular portions are compared. By repeating and comparing these measurements a study of the relative friability characteristics of the grinding wheel and its adaptability for crushing can be precisely determined.

Preferably the gauge head comprises a body 10 having a longitudinal central passage 11 therethrough. A tube 12 fitted about a reduced extension 14 of the body 10 leads through a gauging instrument 15 to a source of air under regulated pressure. Gauging instruments can be provided which measure flow either by gauging the pressure drop across a restriction or by directly measuring the actual rate of flow, and as such devices are well known it is unnecessary to explain here any of the details of the flow gauging device. The particular instrument 15 is one that gives an indication of the air flow.

An annular resiliently yielding sealing member 16 is cemented to the other end of the body 10 within a recess 17. The member 16 is preferably a rubber ring of such. character that its surface when applied to the grinding wheel will conform to all the surface irregularities of the grinding wheel. The body 11 has an annular extension at 18 extending along the axis of the passage 11 and the annular sealing member 16 and terminating in a plane perpendicular to the axis of the passage 11 and the passage through the sealing member 16. The outer surface of the sealing member 16 when free, as illustrated in Figure 2, extends slightly beyond the annular extension 18. Grooves 19 pass radially across the face of extension 18. An annular pocket 20 provided between the sealing member 16 and the annular extension 18 communicates with the grooves 19. The gauging head body 10 is flared at the end thereof adjacent the sealing member 16 for grasping by the operator and easy application in gauging.

Figure 3 illustrates the gauge head as applied to the side surface of a grinding wheel near the periphery or active surface, although it will be obvious that the peripheral surface itself may be tested by applying the gauge head directly to the periphery at different portions. It will be seen that the outward surface of the annular sealing member 16 has been applied under compression and conforms to the surface irregularities of the grinding wheel 25. The compressive application of this sealing member 16 to the grinding wheel 25 is limited by the engagement of the annular extension 18 of the gauging head body 10 with the surface of the grinding wheel. Because the compression is limited to the same predetermined amount upon each application of the gauge head the sealing will be the same and valid comparisons of the measurements are possible. When so applied under compression the sealing member 16 being resilient and yieldable will interfit in sealed relationship with the surface particles of the grinding wheel and surface characteristics of the wheel will not affect the gauging. Gauging air supplied through tube 12 will pass along the passage 11 of the gauging head, through the annular member 16 and into and through the particular portion of the grinding wheel being gauged. At least a portion of the air will be collected in the annular pocket 20 and pass radially out through the grooves 19. It has been found that a measurement of the fiow of air forced into different wheel portions gives an accurate check of relative friability of the wheel portions and the adaptability of the wheel to crushed dressing. The porosity or permeability of the wheel portions will determine the flow and is directly related to the uniformity and relative friable characteristic of checked portions of any particular grinding wheel.

In Figure 1 the gauging head is illustrated as applied in carrying out the method of this invention. In the position as shown in solid lines in Figure 1, the gauging head has been applied to a first portion of the grinding wheel. The flow of air through the gauging head and through the particular grinding wheel portion will be indicated on the instrument 15. When the gauging head is moved to another portion of the grinding wheel as, for example, that shown in phantom lines, the instrument will again indicate the resulting air flow as determined by the characteristics of that particular portion of the grinding wheel. A comparison of the resultant flows will indicate the relative friability characteristics of the gauged portions of the grinding wheel. A complete study of the characteristics of the grinding wheel 25 could be made by applying the gauge head wherever a measurement is necessary. The instrument 15 can be calibrated as desired and, for

example, in a direct comparison measurement a calibration in terms of cubic feet per minute of air flow through the grinding wheel portions can be used.

' Through the application of the method taught by this invention the nondestructive testing of the relative characteristics of different portions of a wheel can be made with precision. Because of the non-destructive character of this method and its simple and economical application, grinding wheels can be pretested for friability to determine their adaptability to crush dressing and grinding, thus allowing their selection without expensive or wasteful procedures. Through its small size and configuration it can be readily applied by hand wherever a measurement is desired. The particular gauging head illustrated is extremely simple in construction and is adapted for a long useful life in gauging both fiat and curved surfaces. The free outer surface of the sealing member of the gauging head is provided to conform in yielding interfitting relationship with the surface of the particular part portion being gauged and structure is provided to insure a uniform compressive engagement with the part surface, making possible repeated accurate gauging operations of this character which can be validly compared.

While the particular application of the method and the particular form of device herein described constitute a preferred application of the method and a preferred device for carrying the method out, it is to be understood that this invention is not so limited and that changes may be applying the conduit in sealed relationship with the same surface area at another location on the same grinding wheel and passing air under the same pressure from the conduit into and through such other grinding wheel portion, and gauging the resultant air flow through such other grinding wheel portion, whereby the relative friability of the gauged Wheel portions is determined.

2. A method of non-destructive gauging of relative characteristics of different portions of the surface of a grinding wheel or the like formed generally of abrasive work forming particles, bond and voids therebetween, to determine the uniformity of distribution of material therein and its characteristics during dressing, forming operations, or the like, comprising the steps of first supplying air under pressure through a predetermined small area of the surface at a first location therealong, gauging the how of air into and through the surface between the abrasive particles at said one location, supplying air under pressure through the surface at other locations therealong but through the same small area for precise comparison I of results, gauging the flow of air into and through the surface and between the abrasive particles at said other locations, and comparing the resultant air flows at the