BACKGROUND OF THE INVENTION
It is customary in drilling the holes for the thumb and selected fingers in a bowling ball to first lay out and mark the location of such holes, together with the grip line to be referred to later herein. For drilling, the ball is set in a cup base which is usually provided with two adjusting screws mounted at right angles to each other for moving the base selected distances along X and Y axes. The base is mounted on the table of a drill press, the axis of the drill press spindle being the Z axis. Pitch index is read in selected fractions of an inch which the ball is moved along the X and Y axes from a position centered on the drill press axis. Complete directions for this prior drilling practice are set forth in a booklet entitled "Bowling Ball Drillers' Manual", No. 7-65 published by Ebonite Company, Division of S. W. Industries, Newton, Massachusetts.
Jigs for use in drilling bowling balls are disclosed in U.S. Pat. Nos. 3,262,339 and 3,263,631, and gauges for measuring pitch and grip span of already drilled holes are disclosed in U.S. Pat. Nos. 3,392,453 and 3,429,049.
PURPOSE OF THE INVENTION
A primary objective of the present invention is to provide a drill pitch indicator which is chucked in a drill press or other drilling mechanism, and, when applied to a bowling ball mounted on the table of the drill press or drilling mechanism, will read out the pitch of a hole to be drilled in the ball at the indicated center when a drill or bit is substituted for the indicator, the ball locked against rotative movement, and the hole drilled at the indicated center.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing objectives and advantages of the invention will be apparent from the following description and the accompanying drawings, wherein:
FIG. 1 is a perspective view of a pitch indicator embodying the invention applied to a bowling ball.
FIG. 2 is an enlarged end view of the indicator.
FIG. 3 is a side elevational view of the indicator.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring to the drawings in detail, an illustrative pitch indicator A for use in the drilling of a bowling ball comprises a stem portion 10 of circular cross-sectional shape, which may be of rod or tubing, with a pair of flanges 11 and 12 fixedly joined to the stem 10 and preferably integral therewith. The flanges 11 and 12 are parallel to each other and to the axis of the stem 10, and are spaced apart on opposite sides of the stem axis to receive a flat index plate 13 in slidable, bearing relation therebetween. The axis of the stem 10 is thus parallel to, and substantially coincident with the mid-plane of the index plate.
The edge 14 of the indicator plate 13 opposite the stem 10 is curved on a circular arc to conform substantially to the curvature of a selected size of bowling ball to be drilled, and a line 15 extending radially of the center of the curved edge 14 is marked on the face of the indicator plate, with an arrow head 17 preferably marked at its point of intersection with the curved edge 14.
A circularly curved slot 18 is provided in the index plate 13, with its center of curvature on the radial center line 15. The index plate 13 is mounted for movement in its own plane pivotally about the center of curvature of the slot 18 by a pair of rollers 19 and 20, journaled on pivot pins 21 and 22 spaced equally from the radial center line 15 in FIG. 3. The roller axes define a plane perpendicular to the stem axis and to the index plate 13, and roll easily with minimum clearance in the curved slot 18 so as to move the index plate 13 pivotally about its elected pivotal center, for example, the point of the arrow head 17 in FIG. 3.
Radial gauge lines 23 are marked at selected spaced intervals along the arcuate slot 18 in both directions from the radial center line 15, each gauge line representing relative incremental movement, for example, one-fourth inch, in a direction parallel to the plane of the index plate 13 and perpendicular to the axis of the stem 10, of the center of a bowling ball to which the curved index plate edge 14 is fitted.
"Forward" and "reverse" pitch is indicated on the gauge 23 by chucking the pitch indicator stem 10 in the chuck C of a drilling mechanism, such as a conventional drill press, and lowering the chuck C to bring the curved edge 14 coincident with a usual grip line 24, to be referred to later herein, marked on a bowling ball B mounted in a cup base 26 on the table D of the drilling machine. Desired forward or reverse pitch is attained by moving the ball in a selected direction parallel to the plane of the index plate 13 while keeping the arrow head 17 on the marked center point of a hole to be drilled in the ball until the desired forward or reverse pitch is indicated on the gauge 23.
"Forward" pitch is that wherein the thumb hole inclines toward the finger holes, or the finger holes incline toward the thumb hole, while "reverse" pitch is that wherein the holes incline in the opposite direction. Side pitch, i.e. right or left pitch relative to the spherical plane of the ball defined by the grip line, is indicated on the gauge 23 by turning the index plate 13 at right angles to the grip line, as by means of the chuck C, and moving the cup base in a selected direction parallel to the new direction of the index plate, in the same manner as described in the preceding paragraph.
In the case of the thumb hole, which is centered on the grip line, right or left pitch is by direct indication on the gauge 23 with the index plate 13 turned 90° to the grip line. However, in the case of the finger holes, which are separated, and ordinarily are located on opposite sides of the grip line, it is necessary to add one-half inch to the required pitch reading in the direction of the finger hole center from the grip line. This factor is well understood by those familiar with the drilling of bowling balls, but a remainder preferably is printed on the index plate as shown in FIG. 3 so there is no danger of the driller overlooking it.
It is assumed that a bowling ball B has been laid out, see FIG. 4, for standard drilling as by means of a conventional layout gauge, not shown, or other suitable means, with usual grip line 24 marking a diametrical plane of the ball through a usual dot 25 or point indicating the center of the top weight of the ball, and perpendicular to the usual serial number 27 engraved on the ball. Also, that the desired location of the thumb hole layout 28 middle finger hole layout 29 and ring finger hole layout 30, including the respective hole centers, are marked thereon.
With the ball thus laid out, the ball is placed in the cup 26a, see FIG. 1, of a suitable ball holder base 26 mounted in a stable manner for slidable movement on the table D of a drilling mechanism such as a conventional drill press. The stem 10 of the pitch indicator A is chucked co-axially in the drilling mechanism chuck C, and the chuck is lowered to bring the curved edge 14 of the index plate 13 onto the ball coincident with the grip line 24 marked thereon. While keeping the curved edge 14 coincident with the grip line 24, and the arrow head 17 on the marked center of the thumb hole layout 28, the cup base 26 is moved slidably on the table in a selected direction parallel to the plane of the index plate 13, and the ball B is moved rotatively in its cup until the gauge 23 reads the desired forward or reverse pitch for the hole to be drilled. In the assumed standard grip, this is zero forward/reverse pitch for the thumb hole.
Since a standard grip for a right-handed bowler has 1/4 inch right hand pitch, the pitch indicator A is then turned 90° about the stem axis by the means of the chuck C, and, with the arrow head 17 centered on the marked center for the thumb hole, the ball is again moved in a selected direction parallel to the plane of the new direction of the gauge plate, and rotatively in its cup around an axis perpendicular to the gauge plate until the gauge 23 reads one-fourth inch right hand pitch.
The ball B is then locked in this position on the cup base 26 by conventional clamp means 31, provided on the cup base, the pitch indicator A is replaced in the chuck C by a drill, not shown, of selected size, the drill is centered on the thumb hole center marked on the ball, and the hole is drilled to required depth, for example, 2 3/4 inches.
The hole for the middle finger is next, and, after replacing the drill in the chuck with the pitch indicator A, and the index plate 13 turned back about its stem axis to its original position, the chuck C is lowered to again position the curved edge 14 coincident with the grip line 24.
With the arrow head 17 retained laterally opposite the center of the layout 29 marked for the middle finger hole, the cup base 26 is moved slidably along the drill press table D, and the ball is moved rotatively in its socket, as explained previously herein for the thumb hole, until the gauge 23 reads three-eighth inch positive pitch. The ball is then locked in this position by the clamp means 31, since no side pitch is specified for the finger holes for a standard grip.
In the event, however, that side pitch should be desired for the finger holes, it may be provided by turning the index plate 90° about the stem axis and proceeding as explained previously herein for the thumb hole, with the exception, however, that one-half inch be added to the reading to allow for the offset of the finger hole from the grip line as mentioned previously herein, and as is customary in prior ball drilling practice.
With the ball B thus locked to the cup base 26, the pitch indicator A is replaced in the chuck C by a drill or bit, not shown, of required size, which is centered on the layout center for the middle finger hole and the hole drilled to required depth, in this case 2 3/4 inches.
Without unlocking the ball from the ball support, the drill for the middle finger hole is replaced in the chuck C by a drill of selected size for the ring finger hole. This latter drill is then centered on the layout center for the ring finger hole, and that hole is drilled to required depth, also 2 3/4 inches.
The holes are then beveled and smoothed in accordance with usual practice to complete the ball, ready for use.
The invention provides a simple, inexpensive pitch indicator which accurately indicates both forward and reverse, and right and left pitch of each hole to be drilled in a bowling ball and since the stem of the indicator comprises in effect the pointer of the gauge, and is replaced co-axially by the drill itself, each hole is drilled with the assurance that the it will have the exact forward or reverse, and right or left pitch as indicated.