Bowling ball drill jig

Aug. 2, 1966

Μ. V. SAMMONS ETAL

3,263,531

BOWLING BALL DRILL JIG

<img file="US3263531A_D0001.tif" />

ATTORNEY.

Aug. 2, 1966

3,263,531

Μ. V. SAMMONS ETAL·

BOWLING BALL DRILL JIG

<img file="US3263531A_D0002.tif" />

Aug. 2, 1966

3,263,531

Μ. V. SAMMONS ETAL

BOWLING BALL DRILL JIG

<img file="US3263531A_D0003.tif" />

Aug. 2, 1966

Μ. V. SAMMONS ETAL

3,263,531

BOWLING BALL DRILL JIG

Filed March 20, 1964

Sheets-Sheet 4

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BY dTTOPNEY.

United States Patent Office

3,263,531

Patented August 2, 1966

3,263,531

BOWLING BALL DRILL JIG

Martin V. Sammons, and Robert D. Baker, Sioux City, Iowa, assignors, by direct and mesne assignments,, to said Sammons, Victor I. Bianchine, South Sioux City, Nebr., and Donald K. Price, Sioux City, Iowa

Filed Mar. 20, 1964, Ser. No. 353,487

Claims. (Cl. 77—62)

This invention relates to improvements in a jig apparatus for drilling the thumb and finger holes in bowling balls and is a continuation-in-part of application Serial No. 340,375 filed January 27, 1964.

With the tremendous increase in popularity of bowling in recent years, many bowlers have acquired their own personal bowling ball in which the finger holes are drilled according to their particular specifications, and such holes are often drilled and redrilled to satisfy the whims and idiosyncrasies of the individual users. There are, of course, a variety of more or less standard finger holes patterns that are provided on rental balls and according to present practices, the substantial portion of drilling the finger holes is done in professional supply shops as distinguished from the actual bowling lane establishments. This can no doubt be accounted for by the fact that the present drill jigs available weigh several hundred pounds, may cost from several hundred to several thousand dollars and require a fixed drill press so that it is economically unfeasible for each bowling lane to own such equipment.

In addition to the cost of drill equipment, the requirement for accuracy in drilling finger holes in bowling balls and the requirement for experienced personnel for operating the jigs makes it impractical for bowling lane proprietors to provide this service as mistakes can be very costly and a few mistakes can render the entire operation unprofitable. However, even with the so-called professional drilling jigs, there are certain problems and disadvantages which we have overcome with our new drill jig as will become apparent.

As is well known, all manufacturers of bowling balls mark on the ball what is known as the center point which is associated with their respective label or name and the drilling of the thumb and finger holes is in reference to such center point since the undrilled ball is heavier at this area so that the ball will be properly balanced after the holes are drilled. The axis of such holes in relation to a direct radius from the contact point of the drill on the surface of the ball is generally inclined forwardly or rearwardly and usually laterally and the exact degree of such inclination, unless of a standard pattern, will depend upon the desired thumb and finger hole positions of the particular user. It will thus be appreciated that the drill point will contact the curved surface of the ball at a tangent relative to the inclination of the hole desired and in present type jigs, experience has shown that this initial contact almost invariably results in a slight drift of the bit along the ball surface before it makes an actual penetration. Such drift, even though small, can and does affect the feel of the ball when considered in relation to all of the holes and is easily detected by experienced bowlers. Since the exact amount of such drift is not always the same on each ball or even on each hole, it cannot be accurately compensated for by varying the initial contact point and consequently extreme accuracy in the drilling of such holes by present apparatus is not generally obtained.

With these observations in mind, one of the important objects contemplated by this invention is the provision of an improved apparatus for drilling thumb and finger holes in bowling balls and more particularly such an apparatus or jig that will result in such holes being drilled with extreme accuracy because of the elimination of any drift of the drill bit relative to the surface of the ball at the initial contact therewith.

More particularly it is an object herein to provide an improved drill jig of the above class wherein the ball is 5 secured in a fixed position and the jig includes not only universally movable apparatus for locating the center point of any hole to be drilled, but also universally movable means to selectively obtain any desired plane for the axis of any hole.

IQ Another important object contemplated herein is the provision of a drill jig as characterized which includes a novel and unique calibrating means for aligning the axis of a drill bit bushing with the center point of any hole to be drilled. In this regard, while the actual contact 15 point on the ball for the drill bit is accurately located, the calibrating means employed is related to the edge to edge distance of the respective holes and automatically compensates for the distance between the edge of the hole and the axial point thereof.

A further important object herein is the provision of a drill jig as indicated and by means of which the holes in the bowling ball may be drilled by any conventional electric hand drill preferably with a chuck of one-half inch capacity. In this regard, we have employed a single drill bit guide bushing having a fixed diameter and have provided drill bits in a variety of sizes but all with the same size shank for cooperation with the guide bushing.

Other objects inherent in this invention are to provide a drill jig of the above class that is durable in construction, 30 economical to manufacture, highly efficient for its intended use and sufficiently light in weight (approximately forty pounds more or less) so that it is easily portable and economically feasible for acquisition and use by individual bowling lanes as well as by professional bowling 35 supply establishments.

Another object of this invention is to provide, with a drill jig as characterized, a novel turret assembly for aligning and guiding a drill bit at any selected angle of inclination and without permitting the drill point to drift 40 relative to the predetermined point on the ball for penetration of such bit.

Further features of this invention reside in its adaptability for use with a finishing tool for the purpose of smoothing the surface of a filler plug placed in a previ45 ously drilled thumb or finger hole and the inclusion of a dust collecting attachment.

To attain these objects and such further objects as may appear herein, or be hereinafter pointed out, reference is made to the accompanying drawings forming a 50 part hereof, in which:

FIG. 1 is a perspective front view of a preferred embodiment of this new drill jig shown with a drill bit bushing in the top thereof and with a bowling ball in place to be drilled,

FIG. 2 is a perspective rear view of the jig shown in FIG. 1,

FIG. 3 is a cross-sectional view taken on the line 3—3 of FIG. 1 but with the jig in opened position,

FIG. 4 is a sectional view of the jig shown in FIG. 1, 60 FIG. 5 is an exploded view of the turret locking assembly taken on the line 5—5 of FIG. 4,

FIG. 6 is a schematic illustration of this jig showing its adjustment for the span between the thumb and finger holes in the bowling ball,

FIG. 7 is similar to FIG. 6 but showing the adjustment of this jig for lateral location of the holes relative to the center point on the bowling ball,

FIG. 8 is a top plan view of the calibration means shown in FIG. 2,

FIG. 9 is a perspective view, partially cut away, of the drill bushing shown in FIG. 1,

FIG. 10 is an elevational view of a drill usable with

3,363,531 ³ a conventional hand drill and adapted for use with the 'bushing shown in FIG. 9,

FIGS. 11-13 are schematic illustrations showing varied common locations of the thumb and finger holes in a bowling ball relative to the center point thereon, 5

FIG. 14 is a perspective view of the tightening knob and calibration means in FIG. 2 with portions broken away to more clearly illustrate the construction thereof,

FIG. 15 is a perspective view illustrating one of a set of different size tabs used in fixing the relative position ιθ of the guide bushing,

FIG. 16 is a perspective view of a collector device for the dust and shavings produced by the drill bit, and

FIG. 17 is a reduced fragmentary perspective view showing the collector in FIG. 16 in place on this new jig. 15

Referring to the drawings, it should be first mentioned that for the most part, all of the substantial portions of this jig 20 are preferably made of aluminum so that its overall weight will be approximately forty pounds more or less. Such lightness in weight has certain commercial 20 advantages and is preferable thereof, but it will be understood that other materials may also be used and the weight thereby increased without in any way departing from the principles hereinafter disclosed.

A generally square hollow base is designated by the 25 numeral 22 (FIGS. 3 and 4) and is provided with a central annular opening 24 defined by the beveled edge 26 for receiving and supporting a bowling ball 28. A plurality of friction tabs 30 of any suitable material such as vinyl or plastic, and preferably not more than one- 30 sixteenth inch thick, are bonded to edge 26 in equally spaced relationship to provide a non-slip contact for ball 28 as will later appear. An annular frame 32 is adapted to overlie base 22 in spaced relationship thereto and for this purpose is hinged as at 34 to the upper end of a 35 hinge support structure 36 secured to the rear side 38 of base 22 as best seen in FIG. 2. Frame 32 is movable as shown in FIG. 3 to permit the placing of ball 28 onto base 22 and is then movable into peripheral contact with the ball 28 for securely clamping it against any relative 40 movement. For this purpose a bifurcated ear 40 on frame 32 diametrically opposite to hinge 34 is adapted to receive the rod 42 pivotally attached at its lower end 44 to the front side 46 of frame 22. The lower portion of rod 42 carries a stop collar 48 and a screwable knob 45 50 on the upper portion of rod 42 can be tightened against ear 40 to provide a suitable locking means designated generally by the numeral 52. The annular ball engaging surface of fram 32 is also provided with friction tabs 54 similar to tabs 30. Thus far described, with a ball 50 28 in jig 20 as shown, the top surface 56 of frame 32 and the top surface 58 of base 22 are parallel and horizontal and for purposes of further description, frame 32 at its hinge point 34 will be referred to as the rear thereof and the location of ear 40 as the front. 55

At oppositely disposed central points on frame 32 on the respective sides thereof intermediate the front and rear of such frame, there is pivotally and centrally mounted the respective elongated parallel support bars 60 and 62 as best seen in FIGS. 1 and 2. The respec- 60 tive corresponding ends of bars 60 and 62 are connected by the respective upwardly extending front and rear arcuate parallel rods 64 and 66 that provide a track means over the ball 28 parallel to the circumference thereof. A carriage 68 is slidably mounted on rods 64 and 66 35 for movement intermediate bars 60 and 62, and a manually operable set screw means 70 is provided to lock carriage 68 against movement from any selected position. Mounted on the top of carriage 68 is the hollow housing 72 in the form of the upper portion of a sphere which is 79 provided with the top opening 74, and it is pointed out that with the continuation of a perimeter line on housing 72 to define a complete sphere, the exact center point of such sphere would coincide with point 76 on ball 28 (FIG. 4) as will be later referred to.

Thus far described it will be understood that housing 72 can be moved toward and away from the respective front and rear ends of frame 32 by pivoting or tilting bars 60 and 62 accordingly and such housing 72 is also movable laterally on tracks 64 and 66 between bars 60 and 62. The movement of housing 72 relative to the front and rear of frame 32 by pivoting of bars 60 and 62 will be referred to as the span gauge and for this purpose a curved calibrated scale 78 (FIG. 2) is mounted to bar 60 intermediate its ends and carries readings of 0 at the scored point 80 to its highest reading of preferably 5 at point 82. There are no markings on scale 78 between point 80 and the end 84 as will be referred to later. There are sixteen calibrations between each number representing one-sixteenth inch on the ball 28 and one thirty one-thousandths of an inch on the scale. A total scale reading representing five inches on ball 28 will be satisfactory in most all circumstances but this may of course be increased if desired. An upstanding support 86 (FIG. 14) on bar 60 is provided with a spring loaded recess or clip means 88 at its upper end for cooperation with scale 78 as will later be explained in detail and tightening knobs 90 and 92 on the respective bars 60 and 62 are manually operable to lock bars 60 and 62 in any selected position. The movement of housing 72 laterally between bars 60 and 62 on tracks 64 and 66 will be referred to as the offset gauge and for this purpose the center portion of the front track 64 (FIG. 1) is calibrated with a scale 94 which carries a reading of 0-1 on each side of center. There are eight calibrations between zero and one at each side and each calibration represents one-eighth inch on the ball 28 and one fortysix-thousandth of an inch on the scale. A pointer 96, having an aperture 98, is carried by carriage 68 and is oriented relative to scale 94 for adjustment of the offset gauge as will later appear.

Housing 72 is designed to carry a turret assembly which is one of the important features of this invention and is indicated generally by the numeral 100 in FIG. 3. In assembly 100, an annular collar 102 with a flat rimlike top 104 has its underside 106 tapered or dished to be complementary with the outside curvature of housing 72 so that it can nest thereon and be universally movable relative thereto to change the inclination of the axis of its central opening 108.

A tightening cap 110 (FIG. 5) for securing collar 102 to housing 72 in relative positions of adjustment comprises an elongated hollow cylindrical shank 112 which is externally threaded at its lower end 114 and terminates at its upper end in a concentrically enlarged shoulder 116 which serves as a manually grippable knob. The spaced peripheral grooves 118 on knob 116 are to facilitate the manual gripping thereof. In mounting cap 110 to housing 72, the washer member 120, and nuts 122 and 124 are used as shown in FIG. 5. With collar 102 on housing 72 as described, washer 120 is placed on the top 104 thereof and the shank 112 of cap 110 is inserted downwardly into housing 72 and into threadable engagement with nut 122 which it will be noted is provided with a radius on its perimeter 126 corresponding to the radius of the inner surface of housing 72 so that it will tightly engage such housing as shank 112 is rotated clockwise in an obvious manner. Shank 112 is long enough to pass through nut 122 and the lock nut 124 is threadably attached to the lower end thereof. Only a slight loosening of cap 110 is required to permit movement of collar 102 and this may be done by grasping knob 116.

For measuring the distance of movement of the turret assembly 100, there are four sets of like calibrations or scales 128, 130, 132 and 134 in the form of respective groups of spaced arcuate lines (FIGS. 1 and 2) in which the spacing is progressively smaller from top to bottom. Scales 128 and 130 are oriented respectively relative to the front and rear of frame 32, and scales 132 and 134 are similarly arranged relative to the respective opposite

3,263,531 ⁵ sides. The distance between each line on such scales represents a distance of one inch on the ball 28. With the bottom edge 136 of collar 102 coplanar with the highest point on the top line on all four scales 128, 130, 132 and 134, the plane of the axis of bore 108 in collar 102 will correspond to a radial line to the center of ball 28 and the bottom of shank 112 will be in closely spaced relationship above the ball 28. A stud or boss 138 extends upwardly from the top rim-like surface of knob 116 for purposes which will be later referred to in more detail.

For use in the operation of jig 20, which will be described in detail, reference is made to FIGS. 9 and 10 showing respectively the drill bit bushing 140 and a representative drill bit 142. Bushing 140 includes the hollow cylindrical shank 144 topped by the flange collar 146 in the perimeter of which is an arcuate notch 148. Bushing 140 is a guide bushing for drill bits 142 for which a set is provided with various size heads 150 but which all include a standard size shank 152 to be received within the bore 154 of bushing 140 and for use with an electric hand drill (not shown). Depth gauge markings 156 may be provided on bits 142 for obvious purposes.

With reference now to FIG. 15, there is shown one of the important novel features of this invention in the form of a tab member 158 which includes a flat rectangular body 160 and a preferably cylindrical short shank 162 projecting perpendicularly from one longitudinal edge at a center point between the opposed ends 164 and 166. A set of tabs 158 are provided with this jig 20 and each one has a different precise dimension relative to the distance between edges 164 and 166 such as one-half, three-quarters or one inch and the like and thus there is a separate tab 158 corresponding exactly in size to each of the drill bits 142 so that corresponding sizes of tabs 158 and bits 142 are used together in drilling the size holes in ball 28 as will later appear. Tabs 158 are used with the span gauge by removably securing shank 162 in clip 88 so that it is oriented with gauge 78 as shown in FIG. 2 and they are used with the offset gauge by inserting shank 162 in aperture 98 of pointer 96 so as to be oriented with scale 94 as best seen in FIG. 1. The function of such tabs will be described more fully with the operation of the entire jig 20.

As an added feature of this invention, we have provided a dust or shaving collector designated generally by the numeral 168 and illustrated in FIGS. 16 and 17. Collector 168 is in the form of a scoop having a projecting bottom 170 with a concave edge 172, sides 174 and 176, and a back 178 and a top 180 which is shorter than bottom 170. Sides 174 and 176 are provided with the notch 182 for receiving track 66 when member 168 is mounted as shown in FIG. 17. In this position, bottom 170 will be closely adjacent the surface of ball 28 near the point of drilling and beneath carriage 68. A tubular fitting 184 in back 178 communicates with the interior of collector 168 and is designed to connect with a suitable hose or fitting (not shown) on any standard or conventional suction or vacuum device which will draw all shavings and dust away as they are created while the ball is being drilled.

Operation

With jig 20 constructed as described, it is used and operated as follows. Frame 32 is opened (FIG. 3) to permit the bowling ball 28 to be placed on base 22 with the center point 186 (FIGS. 11—13) of the ball substantially at point 76 as seen in FIG. 4. Point 186 is easily recognized by those familiar with drilling bowling balls since it will always be found associated with the manufacturer’s label or trademark on the ball and each manufacturer has his own characteristic form of marking the center point. Frame 32 is then returned to closed position (FIGS. 1 and 2), secured by lock or clamp means 52 and the lower edge 136 of . collar 102 is oriented relative to the highest point on the top scale line of cali6 brations 128, 130, 132 and 134 so that the turret assembly 100 is at zero setting.

Ball 28 at this point is ready to be drilled after proper orientation of the jig as will appear, and it is pointed out that at no time during the drilling of either the thumb hole 188 or finger holes 190 and 192 is it necessary to move or remove the ball from its locked-in position in jig 20 and consequently, the accuracy obtainable by this jig is materially greater than in other type jigs where the ball is removed or moved after each hole is drilled to permit proper measurements for the succeeding holes.

In describing the drilling operation with this jig 20, FIGS. 11-13 illustrate different common hole patterns for two finger holes and the thumb hole, and it will be understood that other patterns and a larger number of finger holes may be desired in particular cases. It will also be understood that the size of and relative position of the several holes will have been predetermined either by reference to a standard arrangement or from specifications furnished by the contemplated user of the ball according to his special preferences and that the function of jig 20 is to accurately drill the holes in compliance with such measurements.

The thumb hole 188 is first located and drilled and then the finger holes 190 and 192, and in describing the relative adjustments on jig 20, the thumb hole 188 is toward the front end 46 of base 22 at one side of point 186 and the finger holes 190 and 192 are on the opposite side of point 186 toward the rear 38 of base 22. Any inclination of any of the holes toward the center point 186 will be referred to as forward, and away from point 186 as rearward. Likewise, lateral inclination of any hole will be referred to as a right or left lateral from a reference point at the front 46 of base 22 and as viewed in FIGS. 11-13. The measurement generally between the thumb hole 188 and the finger holes 190 and 192 across the center point 186 is referred to as the span and the measurment between the finger holes is referred to as the bridge. The span may be measured from edge to edge of the holes as shown in FIGS. 11-13 or may be measured from center to center with, of course, proper allowance relative to the reference point used and as will become apparent, we use the edge to edge method. The span may, of course, vary with different users and the four inch span shown is merely illustrative. As seen in FIGS. 11 and 12 the thumb hole and finger holes are equidistant from point 16 which is known as splitting the label and in FIG. 13 most of the span is shown above point 186 which is a preferred arrangement. The relative position of the finger holes 190 and 192 as seen in FIG. 11 and 12 are a matter of choice.

With jig 20 arranged as described and with reference to the generally preferred hole pattern in FIG. 13, the appropriate tab 158 for the desired size of the thumb hole 188 is placed in clip 88 as seen in FIG. 2. Knobs 90 and 92 are loosened so that the span gauge can be moved forwardly until the tab 158 is over the area between points 80 and 84 of scale 78 and edge 164 of the tab 158 registers with the zero scale reading at the score mark or point 80. At this point, clamp 52 is unlatched so that the ball 28 can be fixed in the position it will maintain during the dilling of all of the holes and this is accomplished by manually orienting the ball while sighting through the turret assembly 100 to align the axis thereof generally slightly forwardly of point 186 so that the hole will not impinge upon the label, and in this regard it has been determined from experience that no exact measurements are necessary as long as the first hole to be drilled, being the thumb hole 188, is generally oriented as indicated. Clamp 52 is then locked. With the span gauge and ball thus oriented, knobs 90 and 92 are tightened and the axis of the turret assembly will then be on center with the axis of the hole to be drilled, and on a direct radical line to the actual center or axis of the ball since the lower shank end of the turret as

3,263,531 sembly moves in a parallel plane to the circumference of the ball. The inclination of the proposed hole either forward or rearward or lateral, if desired, or a combination of either a forward or rearward and a lateral inclination is provided by adjustment of the turret assembly 100. For a forward inclination only, collar 102 is moved so that edge 136 registers with the desired line on scale 128 and maintains zero registration with scales 132 and 134. For a rear inclination only, the registrations with scales 132 and 134 are maintained at zero and edge 136 is adjusted relative to scale 130. It will be understood, of course, that the turret cap is loosened to permit movement of collar 102 and tightened once the proper setting is made. In such movement of collar 102, as well as in other adjustments to be described, it is pointed out that because of the spherical plane of the contour of housing 72 having an axial point corresponding to point 76 on ball 28 and the conformation of collar 102 to such contour, that the axial point at the lower end of the shank 114 always remains at the same point over the designated axial point on the proposed hole at the perimeter of the ball and that any movement of collar 102 relative to scales 128, 130, 132 and 134 merely changes the inclination of the turret axis without changing the contact point of the drill bit on the ball as will later appear. For a right lateral inclination only, collar 102 is oriented relative to scale 132 with edge 136 at zero readings on scales 128 and 130 .and for a left lateral only, scale 134 is used and zero readings maintained on scales 128 and 130. It will become apparent from these possible adjustments that both a forward or rear and a lateral inclination can be calibrated simultaneously by orienting edge 136 of collar 102 with scale 132 and either 128 or 130 for example, or simultaneously using scale 134 with 128 or 130 according to the specific measurement for each scale. Having thus set the span gauge and provided for the inclination desired, if any, the thumb hole is ready to be drilled.

The guide bushing 140 may be removed to receive the shank 152 of bit 142, which is inserted therethrough from the bottom end and attached to a hand drill (not shown), and bushing 140 is then replaced in the turret assembly 100. The diameter of collar 146 (FIG. 9) is such that notch 148 can embrace stud 138 to prevent any rotary movement of the bushing. Such bushing and its cooperating turret structure permit the use of any ordinary one-half inch electric drill which is a substantial difference over other jigs of this type that require the use of a heavy drill press. The turret assembly and guide bushing will hold the drill bit directly on line and eliminate any drift of the bit on the circumference of the ball before penetration is accomplished. The weight of the drill with perhaps only a light manual pressure is adequate to accomplish the desired drilling. The depth of such holes vary from what is known as standard, semifinger tip and finger tip depths and for this purpose the calibrated depth gauge marks 156 on the dill bit 142 provide a visible guide means relative to the top edge 146 of bushing 140 for limiting the depth of penetration of the bit 142. Thus far described, in the position of tab 158 on scale 78 with the forward tab edge 164 at score line 80 and the rear tab edge 166 toward scale edge 84, the respective tab edges 164 and 166 corresponds on scale 78 exactly to the edges 164α and 166α of the thumb hole 188 as seen in FIGS. 11-13 and the axis of the tab shank 162 corresponds to the axis of the hole and represents the point of contact on the ball 28 for the bit 142.

The location of the finger holes such as 190 and 192 are all referenced on the thumb hole 188 and reference is first made to FIG. 11 and hole 190 since holes 190 and 188 are shown on the center line 194 so that no offset is necessary in this particular instance. With the thumb hole 188 located and drilled as described, knobs 90 and 92 are loosened to permit movement of the span gauge. Assuming a four inch edge to edge span for holes 188 and 190 for illustration purposes, the span gauge is moved rearwardly causing scale 78 to move relative to tab 158 and this is done until the rear edge 166 of tab 158 registers with the four inch marking on scale 78 whereby the tab edges 164 and 166 on scale 78 represent the edges 1646 and 1666 on hole 190 and the axis of tab shank 162 will correspond to axis of hole 190. This will provide an exact four inch span between edge 166α of hole 188 and edge 1646 of hole 190 with the axial points automatically located and requiring no additional calculation or adjustment. Accordingly, each, finger hole to be drilled can be easily located by reference to the position of scale 78 and tab 158 for the drilling of the thumb hole.

When drilling finger holes as seen in FIGS. 12 and 13 which are offset from the center line 194, the offset gauge must be adjusted as follows. First, an appropriate size tab 158 for the finger hole diameter is selected and shank 162 thereof is inserted in pointer 96 through hole 98 and oriented longitudinally with scale 94 as seen in FIG. 1. The set screw 70 is then loosened so that carriage 68 may be moved left or right for the respective holes 190 and 192. Assuming a quarter-inch spacing or bridge between holes 190 and 192 and with reference to hole 192 for example, the carriage 68 is moved to the right until tab edge 164 (being the left edge in FIG. 1) registers with the one-eighth inch calibration to the right of the zero scale point and thus edges 164 and 166 of tab 158 on the scale 94 will represent edges 164c and 166c on hole 192. For hole 190, the carriage 68 is moved to the left with tab edge 166 registering with the one-eighth scale marking to the left of center. Thus in locating an offset finger hole, only a one-half bridge distance measurement must be referenced for accurately locating the axis of the hole and simultaneously aligning the turret assembly 100 therewith. Any forward, rear, or lateral adjustments desired may then be provided by adjustment of the turret assembly as described for the thumb hole and the holes drilled with the electric hand drill as indicated. The use of the collector, FIGS. 16 and 17, as described is of course optional but is a most efficient and convenient attachment.

The turret assembly of this jig has particular value in drilling the finger holes since the bridge between such holes is normally only one-quarter inch and if two such closely adjacent holes are drilled on a perpendicular axis to the perimeter of the ball at the point of contact, it will be appreciated that the lower extremities of such holes would converge and break through. This is a frequent occurrence in present drilling apparatus and can be eliminated entirely by jig 20 since once the axial point of the finger holes 190 and 192 has been determined by the offset gauge, the axis of the turret assembly is inclined to left for hole 190 and to the right for hole 192 so that the axes of such holes can be parallel to each other or otherwise oriented so they will not break through at the bottom. This will, of course, necessitate the drill bit entering the ball at a tangent relative to the perimeter where the drift of the bit, as described, generally occurs but which has been eliminated by the jig herein disclosed.

This jig 20 when constructed as described may also be used with conventional plug cutter tools. In this regard, as is well known, holes in bowling balls are frequently plugged so new holes can be drilled in perhaps a different pattern or in different degrees of inclination. Such plugging is accomplished by providing a parapet around the hole at the surface and filling the hole with a fluid mixture that will harden according to well-known methods. The resulting plug thus projects slightly from the hole and must be out or smoothed to be coplanar with the outer ball surface. A rotating cutter wheel is generally used and care must be taken to cut the plug accurately so as to gouge or indent the ball as the tool is moved back and forth across the plug. Accordingly, by tightening the turret assembly at all zero reading, forward, rear and lateral, and by loosening the tightening members for both the span and offset gauges, the cutter tool, with

3,263,531 an appropriate depth gauge, may be inserted into the turret assembly through bushing 140 and then rocked forwardly, rearwardly and laterally in its grinding or cutting action against the plug. In this respect, it will be appreciated that such tool will always move parallel to the perimeter of the ball for a uniform cutting action and the depth gauge will prevent further cutting at the required point when the plug is flush with the surface of the ball.

It will be appreciated from the foregoing that jig 20 affords many advantages over the heavy, cumbersome and relatively expensive jigs now available for drilling bowling balls. This jig, because of its relatively light weight and economical cost, may be profitably acquired by individual bowling lane establishments and its adaptability to the use of an ordinary electric hand drill instead of a heavy expensive drill press is a marked departure from and improvement over present methods of bowling ball drilling. Likewise, the fact that the ball is not moved once frame 32 is tightened and the relative simplicity of setting the span and offset gauges by use of tabs 158 and inclination of the hole axes makes the requirement for trained personnel unnecessary.

It is thus submitted that the invention shown and described is aptly suited to achieve the purposes intended and is characterized by a combination of highly useful and mutually cooperating elements that combine their respective and proportionate functions in accomplishing the objects sought to be obtained.

It will be understood that the phraseology employed herein is for the purpose of description and not for limitation and that modifications and changes in the construction and arrangement of this invention can be made within the scope of what is claimed, without departing from the spirit and purpose thereof. It is thus intended to cover by the claims, any modified forms of structure or mechanical equivalents which may be reasonably included within their scope.