US3717956A

US3717956A - Expanding lap arbor

Info

Publication number: US3717956A
Application number: US00097249A
Authority: US
Inventors: A Keatts
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-12-11
Filing date: 1970-12-11
Publication date: 1973-02-27
Anticipated expiration: 1990-02-27

Abstract

An expanding lap arbor which is composed of a pair of telescoped tapered members, which are longitudinally movable relative to each other; the tapered outer member is slit longitudinally and is longitudinally slidable along the tapered inner member by means of a hand wheel so that upon rotation of the hand wheel the outer member will be longitudinally displaced along the tapered inner member thereby expanding the outer member due to its slotted construction at a calibrated amount predetermined for each complete rotation of the hand wheel.

Description

United States Patent Keatts 1 Feb. 27, 1973 EXPANDING LAP ARBOR 2390.916 12 1945 Bothncr .51 [76] Inventor: 3:23 r jg s igg? app Primary Examiner-Othell M. Simpson Attorney-Cullen, Settle, Sloman & Cantor [22] Filed: Dec. 11, 1970 21 Appl. No.1 97,249 [57] ABSTRACT An expanding lap arbor which is composed of a pair of telescoped tapered members, which are longitu- [52] U.S.Cl ..51/l,5l/339 51 Int. cl. .3240 25/00, B24b 27/00, B24b 9/02 3:11: 3 zfrjg lfii f fi figfr f zg 1d of Search ..51 1 338 339 340 346 g Y 3 [58] me dlnally slidable along the tapered inner member by means of a hand wheel so that upon rotation of the [56] References C'ted hand wheel the outer member will be longitudinally UNITED STATES PATENTS displaced along the tapered inner member thereby expandmg the outer member due to its slotted construc- 1,452,769 4/l923 Warner .1 ..51/l tion at a calibrated amount predetermined for each 1,583,010 5/1926 Richardson complete rotation of the hand wheeL 2,694,277 11/1954 3,247,622 4/1966 l-lackman ..51 I165 R 4 Claims, Drawing Figures 4 5 r mmwra PATENTEB FEB27 1975 FIGZ FIG.4

INVENTOR ALBERT B. KEATTS ATTORNEYS EXPANDING LAP ARBOR BACKGROUND AND SUMMARY OF THE I INVENTION gauges, micrometer spindles and anvils, plug rings, 0

thread gauges, holes in jig bushings and die and punch work of fine character must provide surfaces of highly finished condition, which cannot ordinarily be obtained by conventional abrasive grinding, polishing or honing.

The high refinement and surface finish for high precision tools or similar work pieces is accomplished by metal discs, rings, sleeves or the like rotatable members whose surfaces have been charged with a fine flour-type abrasive. The basic material of the lap tool is generally made of a material soft enough to permit the abrasive substance to be pressed into the surface of the lap. So treated the tool is said to be charged."

The ideal abrasive for lapping is one which will break-down or become finer as the lapping proceeds. Two general types of abrasives are normally available for lapping, which are: natural abrasives and manufactured abrasives. The first group may include materials such as emery, corundum, rouge, oxide of chromium, oxide of tin, quartz and diamond dust, etc. Compounded abrasives, available in powder and paste forms, may be brushed orsprayed on for best results.

Obviously, precision bores or other precision surfaces on certain tools or other work pieces which have to be lapped to obtain a micro-fine finished surface, are subject to previous machining tolerances which, however small, affect the required precision dimensioning of these particular surfaces. Similarly, as the lapping operation proceeds with regard to these surfaces, the brushed or sprayed on lapping compound, as mentioned above, breaks-down and becomes finer, thus, eventually reducing the over-all dimension of the lapping tool, including the abrasive compound, as initially employed. Likewise, the surface of the work piece or precision part which is being lapped, during the lapping operation, changes its dimension as material is being removed from the surface by smoothing out the initial roughness of the surface. Consequently, lapping tools in order to be effective for the required fine finishing operation, during any one lapping operation, have to be adjusted in accordance with material removed from the surface of the work piece as well as from the abrasive compound of the lapping too]. Ordinarily, this requires periodic shut-down of the machine tool on which the lap is employed and the lap dimensions have to be rechecked and the tool or work piece accordingly reset to continue lapping operation at an increased expense of down-time and additional man-hours.

Ordinarily, the lap should be kept as tight as possible against the surface or within the hole to be lapped. Thus, if the lap is kept tight against the surface, it will correct out-of-roundness, taper, bell-mouth and bowed conditions along the surface to be finished. Likewise, the lap at all times should be kept moist, with the lapping compound or oil to prevent seizing or burnishing, but in such fashion as not to permit to collect lapping compounds near the ends of the lap which will produce a bell-mouth condition in the finished hole.

In normal application, the speed of lapping actually removes more stock faster than any grinding or honing operation, if the proper lapping compound is used and if the lap is being adjusted against the surface at frequent intervals. For example, a inch diameter lap will remove 0.0001 inch of a surface in 2 to 3 seconds with a 600 grit lapping compound. After the 2 or 3 seconds time the part is sliding on the lap and is not cutting, which means the lap must be adjusted again. If the lap is adjusted often enough and a sufficient (not excessive) supply of compound is used, holes under 74 of an inch diameter can be lapped faster than by grinding or honing and with far more accuracy and less initial investment.

Accordingly, the present invention provides an improved lapping tool which can be adjusted indefinitely between predetermined limits in a fast and accurate manner requiring no excessive shut-down of the machine tool for rechecking and resetting the lap or the tool respectively.

The lapping tool of the present invention is composed of a pair of telescoped members, each of which is tapered longitudinally. The outer tubular, tapered member is longitudinally or spirally slotted and the members are arranged for longitudinal displacement relative to each other so that, as the outer member is drawn over the inner member, the outer member is forced to expand in correspondence with the degree of taper between the members by means of its slotted condition. The slotted, tapered outer member of the present improved lapping tool is attached to an adjusting knob co-axial with the lapping tool. The adjusting knob is rotatable around the inner tapered member, so that when the adjusting knob is rotated the slotted, tapered outer member will be drawn over the tapered inner member, or vice-versa, to thereby infinitely adjust the diameter of the tapered outer member in accordance with the amount of material removed from the lapping compound adhered to the outer member of the lapping tool or respectively, from the surface of the work piece.

The arrangement of the present improved adjustably expandable lapping tool is calibrated such, that a full 360 rotation of the adjusting knob causes expansion of the slotted, tapered outer member at predetermined increments in relation to the actual :size of the individual lapping tool.

The helical or spiral slot of the outer member of the improved lapping tool, produces a uniform radial lap expansion accounting for a faster lapping action and BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate a preferred embodiment of the present invention in which:

FIG. 1 represents a longitudinal cross-section through the present improved expandable lapping tool in accordance with the present invention;

FIG. 2 is an enlarged transverse cross-section through the telescoped, tapered arbor and lap members of the present invention as seen in the direction of the arrows 2-2 in FIG. 1;

FIG. 3 is a separate perspective illustration of the present improved expandable lapping tool construction incorporating the features of the present invention; and

FIG. 4 is a fragmentary view similar to FIG. 3 of a modification.

DETAILED DESCRIPTION OF THE INVENTION With reference now to the attached drawings, FIG. 1 illustrates a lapping tool assembly, generally indicated at 10, which is constructed in accordance with the present invention and which includes a shank member or stub shaft 12 which has an intermediate reduced diameter portion 14 and a radial flange 16 substantially intermediate it ends. The inner end of the shank member 12 is externally threaded as at 18 for threading engagement within the sleeve 20 of an adjuster assembly 22.

The externally threaded portion 18 of the shank member 12 is axially providedwith a tapered bore 24 which axially inwardly terminates in a blind, threaded bore portion 26.

The tapered bore 24 in the shank member 12 is adapted to receive the tapered head portion 28 of an inner longitudinal arbor member 30 adapted for axial extension through the adjuster member 22 and outwardly thereof. The inner end of the longitudinal arbor member 30, adjacent the tapered head portion 28, is provided with an externally threaded end 34 for threading engagement within the threaded bore portion 26 of the shank member 12. Thus, when the threaded end 34 of the longitudinal inner arbor member 30 is threaded into the threaded bore portion 26, the tapered head portion 28 of the inner arbor member will be wedged into tight engagement within the tapered bore portion 24 of the shank member 12 of the lapping tool assembly.

In assembly, as seen-in FIG. 1, the shank portion 12 of the lapping tool assembly is adapted to be clamped into the spindle or head portion 11 of a lathe, drill press or similar machine tool to be securely held therein, as is known practice; the intermediate radial flange 16 abutting against the face'of the spindle or head 11, as is shown, to limit inward extension of the shank portion 12.

The inner longitudinal arbor member 30 extends into a tapered rod portion 36 which is composed of two identically tapered sections 38 and 40 connected by a shoulder portion 42. The tapered sections 38 and 40 taper in a converging direction outwardly of the adjuster assembly 22, providing a small diameter end portion 44.

The inner tapered arbor member 30 is adapted to be telescopically received with a tubular, similarly tapered, outer member or lap member 46 which is provided with an internal and external taper corresponding to the external taper of the inner arbor member 30 so as to be slidingly fitted thereon. The inner end of the external, tubular, tapered lap member 46 extends into the adjuster member 22 and is therein provided with an enlarged radial head portion 48 providing a shoulder 50 between the head portion 48 and the shank portion of the tubular external lap member.

The enlarged head portion 48 of the external lap member 46 is supported within a bushing, needle bearing or the like 52, radially press fitted within the adjuster assembly 22. As seen in FIG. 1, the needle bearing 52 is of substantially identical axial extension as the enlarged head portion 48 and the needle bearing 52, together with the enlarged head portion 48, are held in clamped relationship within the body portion of the adjuster member 22 by means of a pair of opposite thrust bearings 54 and 56 respectively. The outer thrust bearing 54 is maintained against axial movement between the ends of the needle bearing 52 and the shoulder 50 and an internal radial flange 58 extending internally of the adjuster member 22. The enlarged head portion 48, thrust bearings 54 and 56 and needle bearing 52, are clamped in axially retaining relationship within the adjuster member 22 by means of a lock nut 60, threaded into the threaded sleeve portion 20 of the adjuster member tightly against the inner thrust bearing 56, as shown.

The body portion 21 of the adjuster member 22, outwardly of the internal radial flange 58, is provided with an axial recess 62, the bottom of which is formed by the flange 58. Recess 62 is adapted to receive a seal assembly 64 for sealing engagement circumferentially around the external surface of the outer tubular lap member 46, which is adapted for longitudinal sliding movement therethrough, as will be described hereafter.

With particular reference to FIG. 3, the larger portion of the tapered outer tubular lap member 46 is longitudinally slotted, as indicated at 66, along a plurality of radially equally spaced locations (in this instance four) to thereby permit flexible, circumferential, radial outward expansion of the tubular outer member 46 upon relative longitudinal movement of the shank 36 of the arbor member 30 therethrough, as will be explained in the following.

As described, the adjuster member 22 is rotatable around the threaded shank portion 18 due to the threaded engagement of its sleeve 20 therewith and is provided with an external hand wheel or knob 68, integrally formed with the body portion of the adjuster member 22.

The slotted tubular and tapered outer member 46 is adapted to be provided with a lapping compound powder of a material suitable for any particular lapping operation in correspondence with the respective hardness of the work piece being lapped. Most commonly used lapping abrasive compounds or powders are, for instance, aluminum oxide for the use on soft metals; silicon carbide, suitable for lapping of hardened metals which, however, due to their scratch characteristic, are restricted to such parts as gears, large valve bodies, etc., and boron-carbides for lapping of extreme hard metals such as tungsten and tantulum carbides and other lapping jobs which previously required the use of diamond tools.

Commonly, the lapping compound or powder is applied to the slotted tubular outer member 46 by means of a brush or the like, whereby portions of the compound is made to flow into the slots 66, providing additionally a convenient storage space for the lapping compound. The metal of which the slotted tubular outer member 46 is being made, is usually an annealed iron and in any case is softer than the material being lapped. After the slotted outer lap member 46 has been thoroughly coated with the respective lapping compound, the initial operation will be to reciprocate the part to be lapped several times back and forth over the lap before the lap is expanded in tight engagement against the surface of the part. This assures that the compound will be distributed evenly and the compound will impregnate the lap surface, i.e., slotted outer member 46, whereafter the lap is expanded in a tight engagement against the surface of the part to be lapped.

The lap assembly as illustrated, for example, is adapted to precision lap bores in a particular work piece. Initially, the lap must be expanded tight into the hole to be lapped and, thereafter, the lap must be periodically radially expanded in small increments in correspondence to the amount of material being removed from the work surface and the lapping compound adhering to the surface of the outer lap member.

This is accomplished by the improved feature of the adjuster assembly 22 which permits radial expansion of the slotted lap member 46 in small increments. The outer surface of the hand wheel or knob 68 will be knurled or otherwise roughened to facilitate manual rotation of the adjuster assembly 22. Thus, as the ad juster assembly 22 is rotated on the threads 18 of the holding shank 12 of the lap assembly 10, the slotted tubular outer lap member 46 is drawn inwardly, that is, to the spindle ll of the machine tool over the tapered surface of the inner arbor member 30. This is accomplished by means of abutment of the outer thrust bearing 54 against the shoulder 50 of the head portion 48 of the outer lap member 46, which is disposed in the adjuster assembly 22 within the needle bearing 52. Thus, as the slotted tubular outer lap member 46 is drawn over the tapered inner arbor 30, the slots 66 of the outer lap member permit radial expansion of the outer lap member at infinite predetermined increments. In a particular example, for instance, the radial expansion of the slotted tubular outer lap member 46 is indexed at 0.005 of an inch for each complete 360 rotation of the adjuster assembly 22. The limit of the adjustment is reached when the outer end 44 of the tapered inner arbor 30 is flush with the small end of the tubular outer lap member 46.

Thus, the present invention provides an improved, highly effective expansion means for a lapping tool which does not require a prolonged shut-down and repositioning of the tool or work piece for adjustment of the lapping tool within the bore which is to be lapped. The expandable adjustment of the lapping tool by means of the present improved constructionis accomplished in a matter of minutes without disassembling the work piece or the lapping tool from the machine tool.

The provision of a rotatably adjustable member attached to the inner end of the slotted outer lap member permits the slotted outer lap member to be drawn over the tapered inner arbor for radial expansion of the outer lap member at predetermined increments by merely turning the adjuster member in the desired direction.

As an alternate embodiment, instead of the longitudinal slots 66 in the tubular outer lap member 46, the member 46 can be provided with a continuous spiral slot 66 having a suitable helix angle. In this instance, the slotted outer lap member when drawn over the tapered inner arbor, uncoils like a spring, due to the spiral slot arrangement, and equally along the entire length of the taper of the inner arbor, the expansion being at the same rate along the entire taper length, assuring complete roundness of the outer lap member in any adjustably expanded position.

Although the present invention has been shown and described by means of a preferred embodiment, it will be obvious that various modifications in the arrangement and structural details may be asserted to without departing from the spirit and essential characteristics of the invention as defined by the scope of the appended claims.

lclaim:

1. In combination with a machine tool having a driven spindle and a lapping tool secured to said spindle for driving engagement therewith; said lapping tool having a threaded shank adapted for clamping engage ment within said spindle; an inner arbor axially secured within said shank having a longitudinally tapered portion extending axially from said shank; a tubular lap member mounted over the tapered portion of said inner arbor; said lap member having a tapered configuration corresponding to said arbor; said lap member being adapted for sliding movement along said arbor; adjusting means operably connected between said lap member and said shank including thread means to permit rotation and thus axial movement of said adjusting means along said shank; said lap member being slotted longitudinally so that upon rotation of said adjusting means and consequent axial movement thereof along said shank, said lap member will be drawn over said inner arbor to thereby cause radial outward expansion of said lap member; said thread means comprising an internally threaded sleeve threaded upon said shank; said sleeve surrounding said inner arbor; said tubular lap member having an enlarged head inwardly of said sleeve; and means inwardly of said sleeve to radially and axially confine said enlarged head within said adjusting means; said means to confine said enlarged head comprising a pair of thrust bearings adjacent opposite ends of said enlarged head; said sleeve having an internal radial flange for axial abuttment of one of said thrust bearings; and a lock nut threaded into said sleeve for tightening the other of said thrust bearings against the outer end of said enlarged head.

2. In the machine tool of claim 1, and a radial bearing within said sleeve disposed around said enlarged head to facilitate rotation of said adjusting means therearound.

3. In the machine tool of claim 2, there being a counter-bore at the outer end of said sleeve; and a seal in said counter-bore for engagement around said lap member.

4. In the machine tool of claim 1, said adjusting means having a radial flange for manual rotation of said adjusting means.

Claims

1. In combination with a machine tool having a driven spindle and a lapping tool secured to said spindle for driving engagement therewith; said lapping tool having a threaded shank adapted for clamping engagement within said spindle; an inner arbor axially secured within said shank having a longitudinally tapered portion extending axially from said shank; a tubular lap member mounted over the tapered portion of said inner arbor; said lap member having a tapered configuration corresponding to said arbor; said lap member being adapted for sliding movement along said arbor; adjusting means operably connected between said lap member and said shank including thread means to permit rotation and thus axial movement of said adjusting means along said shank; said lap member being slotted longitudinally so that upon rotation of said adjusting means and consequent axial movement thereof along said shank, said lap member will be drawn over said inner arbor to thereby cause radial outward expansion of said lap member; said thread means comprising an internally threaded sleeve threaded upon said shank; said sleeve surrounding said inner arbor; said tubular lap member having an enlarged head inwardly of said sleeve; and means inwardly of said sleeve to radially and axially confine said enlarged head within said adjusting means; said means to confine said enlarged head comprising a pair of thrust bearings adjacent opposite ends of said enlarged head; said sleeve having an internal radial flange for axial abuttment of one of said thrust bearings; and a lock nut threaded into said sleeve for tightening the otheR of said thrust bearings against the outer end of said enlarged head.