Precision locating and dividing methods

by Anonymous

It had been decided that no screws should be used in attaching the buttons or disks to the work, as it was feared that the tapped holes would introduce inaccuracy by deflecting the boring-tools; therefore the following method was employed. After all the disks were fastened in place by clamps, a soft solder of low melting point was flowed about them, filling the work to the top of the rim. When the solder had cooled, the clamps were removed, the work transferred to the lathe faceplate, indicated in the usual way, and the holes bored by a “D” or “hog-nose” drill, guided by an axial hole in each disk, which had been provided for that purpose when the disks were made. It was thought that the unequal contraction of the solder and the plate in cooling might throw the holes “out of square;” however, careful measurements failed to show any appreciable lack of parallelism in test-bars inserted in the holes.

Fig. 12.Locating Holes at an Angle by use of Disks and Buttons

Fig. 13. Locating Holes by Means of Two- and
Three-Diameter Disks in Contact

Accurate Angular Measurements with Disks

For setting up a piece of work on which a surface is to be planed or milled at an exact angle to a surface already finished, disks provide an accurate means of adjustment. One method of using disks for angular work is illustrated at A in [Fig. 14]. Let us assume that the lower edge of plate shown is finished and that the upper edge is to be milled at an angle a of 32 degrees with the lower edge. If the two disks x and y are to be used for locating the work, how far apart must they be set in order to locate it at the required angle? The center-to-center distance can be determined as follows: Subtract the radius of the larger disk from the radius of the smaller disk, and divide the difference by the sine of one-half the required angle.

Fig. 14. Obtaining Accurate Angular Measurements with Disks

Example: If the required angle a is 32 degrees, the radius of the large disk, 2 inches, and the radius of the small disk, 1 inch, what is the center-to-center distance?