Edited by H. Walrond
On careful investigation the present method of measuring pinhole golds proves itself open to several objections. A process that is accurate, simple, and can be quickly completed is the ideal one, and it is claimed that the one at present in use is wanting in every one of these essential qualities.
The first objection to the present system is that the pin-hole gold card, having to enclose the arrow on three sides, cannot fit closely owing to the very slightly but still varying thickness of certain arrows (Fig. 1.); consequently, when the quadrilateral is completed and the diagonals are drawn, their point of intersection does not coincide with the centre of the arrow, as the quadrilateral is not the square circumscribed round the arrow (Fig. 2). This error in itself, everything else being correct, would be very small unless the card grossly misfitted; but it is liable to become far more serious when the second step in the process to which objection is raised takes place, viz., marking two points on the card (e and f, Fig. l),so as to enable the quadrilateral, if necessary, to be completed. It is scarcely necessary to point out the difficulty of marking these two points so that the straight line joining them shall be at right angles to the edges of the opening in the card if this opening is too wide, and the card consequently liable to slip, or too narrow, and the card therefore liable to bulge or even to split in half. In addition to the above-mentioned drawbacks, the process is most tedious; the card has to be marked in at least six places, and, should another pin-hole gold be made, has to be reversed, and is then exhausted, and, finally, for the all-important purpose of comparison, the measurements have to be transferred and diagrams constructed, necessitating the use of mathematical instruments, with inevitable multiplication and exaggeration of existing errors.
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Now for the proposed method. This is similar to that in vogue for measuring ordinary golds, when all men's arrows are assumed to be of one uniform diameter, slightly exceeding the uniform diameter of all ladies' arrows. On this particular subject more will be said later; but it will suffice for the present to state that this difference between the average diameter of arrows used by either sex is .88 mm. (.034 inches).
The apparatus consists of a light triangle or triangular frame with angles of 45°, 45°, and 90°, and each of the equal sides should measure 140 mm. (5.5 inches) from extremity to extremity. A small incision each side of which measures 4 mm. (.16 inches) is made at the junction of and at right angles to the two equal sides of the triangle. Two lines of reference are then carefully drawn on each of the equal sides at the exact points where the circumference of the gold circle meets the edges of the frame when the same is placed against an absolutely central arrow of either kind (Figs. 3 and 4). It is obvious that when the frame is placed against an absolutely central arrow of the smaller diameter, the reference marks, where the gold circle outs the equal sides, will lie a little outside the reference marks when the frame is applied to an arrow of the stouter kind. All that remains to be done in measuring a pin-hole gold after placing the frame against the arrow is to revolve it with the arrow as centre until the appropriate reference mark on either side lies exactly on the circumference of the gold circle, and the difference between the corresponding reference mark on the opposite side and the circumference of the gold circle will be the distance between the centre of the arrow and the centre of the gold (Fig. 5). The lines in each pair of reference marks should be .44 mm. (.017 inches) apart—.5 mm. (.02 inches) is near enough, The position of any pin-hole gold can be almost instantly ascertained and noted, and if a second is made, a comparison is possible on the spot exactly as in measuring an ordinary gold. The frame can be used for measuring ordinary golds, as the space between the reference marks and the incision is available—is, in fact, an ordinary gold measuring card. The frame or triangle can be constructed out of stiff but thin cardboard by cutting out a triangle of the dimensions given. The reference marks can then be measured off on either side—121.9 mm. (4.80 inches) from the apex for the stouter arrows, 122.3 mm. (4.82 inches) for the more slender. The incision must then be made so that the piece removed is a perfect square, each side measuring 4 mm. (.15 inches). Small set squares of pear wood can be purchased which will answer the purpose well, as pencil marks can be easily made and erased on this surface, and the reference marks can be cut in with a sharp knife. The only objection to these is that they are rather too thick.