Measuring Tools/Chapter 4

Among the miscellaneous measuring tools and gages dealt with in this chapter are tools and gages for measuring and comparing tapers, adjustable gages, radius gages, gages for grinding drills, sensitive gages, tools for gaging taper threaded holes, contour gages, etc. Of course, these are offered merely as examples of what can be done in the line of measuring tools for different purposes, and, while having a distinct and direct value to the mechanic, they also have a great indirect value, because they furnish suggestions for the designing and making of tools for similar purposes.



Fig. 45 shows a tool which has proved very useful. It is a tool for measuring tapers on dowel pins, reamers, drill shanks, or anything to be tapered. Most machinists know that to find the taper of a shank they must use their calipers for one end and reset them for the other end; or else caliper two places, say, three inches apart, and if, for instance, the difference should be 1/16 inch, they must multiply this difference by four to get the taper per foot. With the tool above mentioned, all this trouble in calipering and figuring is saved. Simply place the shank or reamer to be measured between pins A, B, C, and D, and slide H and K together. Then the taper can be read at once on the graduated scale at L. The construction of the tool will be readily understood. The body or base F has a cross piece supporting the two pins A and B. On this slides piece K, which has at its right end the graduated segment. The screw G is fast to piece K, and upon it swivels the pointer E, which carries the two pins C and D. Thus these two pins can be brought into contact with a tapered piece of any diameter within the capacity of the tool, and the swivel screw G allows the pins to adjust themselves to the taper of the work and the pointer E to move to the left or right, showing instantly the taper per foot.

As the pins A and B are 1½ inch apart, which is ⅛ of a foot, and the distance from G to L is 4½ inches, which is three times longer than the distance between A and B, the graduations should be 3/64 inch apart, in order to indicate the taper per foot in eighths of an inch.



A handy taper gage is shown in Fig. 46. The blades of the gage are made of tool steel. The edge of the blade A is V-shaped, and the blade B has a V-groove to correspond. The end of B is offset so as to make the joint and allow the two blades to be in the same plane. A strong screw and nut are provided to hold the blades at any setting. The user of this gage looks under the edge of A, and is thereby enabled to tell whether the taper coincides with that set by the gage, and also where a taper piece needs touching up to make it true.



In steam injector work, accurately ground reamers of unusual tapers are commonly required, and the gage shown in Fig. 47 was designed to maintain the prevailing standard. It consists of a graduated bar, 1 inch square, with the slot F running its entire length. The stationary head A is secured in position flush with the end of the bar, and the sliding head B is fitted with a tongue which guides it in the slot. This head may be secured in any desired position by means of a knurled thumb nut. The bushings D and are made of tool steel, hardened and ground to a knife edge on the inside flush with the face. All bushings are made interchangeable as to outside diameter.

The head B is fitted with an indicating edge E which is set flush with the knife edge of the bushing. The reading indicates to 0.010 inch the distance the bushings are from each other, and the difference in their diameter being known, it is easy to compute the taper. With this gage it is possible to maintain the standard tapers perfectly correct, each reamer being marked with the reading as shown by the scale.



Fig. 48 shows an inside and an outside adjustable gage for accurate work, used in laying out drill jigs, and in setting tools on lathes, shapers, planers, and milling machines. The outside gage is shown in the side view and in the sectional end view marked Y. At X in the same figure is a sectional end view showing how the gage is constructed for inside work. The top and bottom edges are rounded, so that the diameters of holes may be easily measured.

The gage consists of a stepped block B, mounted so as to slide upon the inclined edge of the block C. There are V-ways upon the upper edge of the latter, and the block B is split and arranged to clamp over the ways by the screw shown at S. All parts of the gage are hardened and the faces of the steps marked A, are ground and finished so that at any position of the slide they are parallel to the base of the block C. The lower split portion of the block is spring-tempered to prevent breaking under the action of the screw, and also to cause it to spring open when loosened. The gage has the advantage that it can be quickly adjusted to any size within its limits, which does away with using blocks. In planing a piece to a given thickness, the gage may be set to that height with great accuracy by means of a micrometer caliper, and then the planer or shaper tool adjusted down to the gage. This method does away with the "cut-and-try" process, and will bring the finishing cut within 0.001 inch of the required size. If the piece being planed, or the opening to be measured, is larger than the extreme limit of the gage, parallels may be used. In fitting bushings into bushing holes, the adjustable gage may be moved out to fit the hole, and then, when the bushing is finished to the diameter given by the gage, as determined by a micrometer caliper, a driving fit is ensured.



Fig. 49 shows a radius gage which has proved to be very handy for all such work as rounding corners or grinding tools to a given radius. The blades are of thin steel, and are fastened together at the end by a rivet, thus forming a tool similar to the familiar screw pitch gage. The right-hand corner of each blade is rounded off to the given radius, while the left-hand corner is cut away to the same radius, thus providing an instrument to be used for either convex or concave surfaces. The radius to which each blade is shaped is plainly stamped upon the side.



Fig. 50 shows a gage for use in grinding drills, which has been found very handy and accurate. This gage enables either a large or small drill to lie solidly in the groove provided for it on top of the gage, and the lips can then be tested for their truth in width, or angle, much easier and quicker than with the gages in common use without the groove. There is a line, to set the blade B by, on the stock at an angle of 59 degrees at the top of the graduated blade, and the user can easily make other lines, if needed for special work. The blade is clamped in position by the knurled nut N at the back, and can be thus adjusted to any angle. The stock A is cut away where the blade is pivoted on, so that one side of the blade comes directly in line with the middle of the groove.



The tool shown in Fig. 51 is used for gaging taper threaded holes in boilers when fitting studs. It is a simple, though very useful and economical tool, and it will doubtless be appreciated by those having much work of this kind to do. The hole in which the stud is to be fitted is calipered by filling the threads of the plug with chalk, and then screwing the plug in the hole. When the plug is removed the chalk will show exactly the largest diameter of the hole.





Figs. 52, 53 and 54 illustrate a special tool which will be found of great value in certain classes of work. The need of some such device becomes apparent when patterns and core boxes are required to be accurately checked with the drawings of brass specialties, in particular. The tool is applied to the work, and the wires pressed down onto the contour by using the side of a lead pencil. Of course, patterns parted on the center could have their halves laid directly on the drawing without using the contour gage, but some patterns are cored and inseparable. Such a tool proves a relentless check upon the patternmaker, who, by making the patterns larger than necessary, can cause a considerable loss in a business where thousands of casts are made yearly from the same patterns. As a ready and universal templet it is very useful.





A reliable way for testing the pitch of a lead-screw, at any position of its length, is to procure a micrometer screw and barrel complete, such as can be purchased from any of the manufacturers of accurate measuring instruments, and bore out a holder so that the axis of the micrometer screw will be parallel to the holder when the screw is in place, as shown in Fig. 55. With the lathe geared for any selected pitch, the nut engaged with the lead-screw, and all backlash of screw, gears, etc., properly taken up, clamp the micrometer holder to the lathe bed, as shown in Fig. 56, so that the body of the holder is parallel to the carriage. Adjust the micrometer to one inch when the point of the screw bears against the carriage and with a surface gage scribe a line on the outer edge of the faceplate. Now rotate the lathe spindle any number of full revolutions that are required to cause the carriage to travel over the portion of the lead-screw that is being tested, bringing the line on the faceplate to the surface gage point. If the distance traveled by the carriage is not greater than one inch, the micrometer will indicate the error directly. For lengths of carriage travel greater than one inch, an end measuring rod, set to the number of even inches required, can be used between the micrometer point and lathe carriage. The error in the lead-screw is then easily determined by the adjustment that may be required to make a contact for the measuring points between the carriage and the micrometer screw. The pitch can be tested at as many points as are considered necessary by using end measuring rods, of lengths selected, set to good vernier calipers. The style of holder shown can, with the micrometer screw, be used for numerous other shop tests, and as the screw is only held by friction caused by the clamping screw, it can easily be removed and placed in any form of holder that is found necessary.





Fig. 57 shows a very simple, but at the same time, a very ingenious tool for measuring angles. Strictly speaking, the tool is not intended for measuring angles, but rather for comparing angles of the same size. The illustration shows so plainly both the construction and the application of the tool, that an explanation would seem superfluous. It will be noticed that any angle conceivable can be obtained in an instant, and the tool can be clamped at this angle by means of screws passing through the joints between the straight and curved parts of which the tool consists. Linear measurements can also be taken conveniently, one of the straight arms of the tool being graduated. As both of the arms which constitute the actual angle comparator are in the same plane, it is all the easier to make accurate comparisons. This tool is of German design, and is manufactured by Carl Mahr, Esslingen a. N.



In Fig. 58 is shown a sensitive gage for inspecting small bevel gears. The special case shown to which the gage is applied in the engraving is a small brass miter gear finished on a screw machine, in which case some of the holes through the gears were not concentric with the beveled face of the gears, causing the gears to bind when running together in pairs. The gage shown is quite inexpensive, but it indicates the slightest inaccuracy.