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74 MACHINE TOOL :ATTACHMENT FOR BORING ANGULAR HOLES. The convenience of square holes and of square counter-sinks in certain classes of construction has long since directed the attention of inventors to the problem TAE Marine REVIEW it will be seen that when one side of the shank is either rolling or sliding upon one side of the square guide, the opposite edge of the shank will move straight line. This holds true for all positions of the shank except for a very small distance at the corners, and it is ea) SHOWING APPARATUS ATTACHED TO HEAD OF AN ORDINARY LATHE. of producing such holes in wood, metal, etc., at a single operation. We are now able to describe a device by means of which it is possible to bore such holes upon any ordinary lathe, milling machine, or drill press at a rate nearly equal to the speed at which ordinary round holes can be drilled with a flat or twist drill. Of course, it goes without saying that for a solid tool to bore anything more than round holes it must have something more than a 'purely rotary motion about a fixed axis, and the interest of the present appliance consists in the mechan- ism by which the proper motion is ob- tained. This. is .a special : chuck,. illustrated herewith, consisting essentially of three Parts; first, a driving "part, which 'is screwed to the spindle of the machine upon which the work is done; second, a stationary part, which may either ride upon the first part, by means of a bear- ing, or which may be fastened directly to the frame of the machine, and third, a part into which the shank of the drill is screwed and which is caused to rotate by the first part, but which is also free to move sidewise to a certain extent. This sidewise motion is limited by a guide or matrix in the second or stationary part, the exact amount and form of the mo- tion being determined by the shape of this guide and by the shape of the shank of the tool. The tool for boring square holes has a three-cornered shank, the sides being segments of circles struck from the op- posite angles or edges as centers, and the radius of all three circles being the same and equal to one side of the square guide in which the shank turns about. By reference to the diagram shown herewith found that the tool here described bores a square hole with slightly rounded corn- ers. If it is desired to bore a square hole with sharp corners, a special tool is DETAILS OF CONSTRUCTION. im a employed having a shank considerably larger than the cutting head, one of the corners of the shank being rounded in- stead of angular. The exact form of this shank has been worked out empiri-' cally and standards have been made for all the sizes of holes likely to be needed in practical work. The cutting edges of the tool are on the end, as in the case of either flat or r a a Se ae; twist drills. To do commercial work with this device, it is necessary to have as many different drills as there are sizes of holes to be bored, but the matrix or guide in the stationary part of the chuck can be adjusted to a considerable range of sizes, making only one chuck neces- sary. Where it is desirable to bore triangular, pentagonal or hexagonal holes or other forms of holes, a corresponding tool and matrix is supplied. It is found, however, that the square hole is of the most general utility. A large number of these chucks, prac- tically all of which are of the square hole type have been sold in Germany to such icnoniamaeliaciamianiereoi