Fig. 7. Set of Boring Mill Tools
Turning Tools for the Vertical Boring Mill.—A set of turning tools for the vertical boring mill is shown in [Fig. 7]. These tools can be used for a wide variety of ordinary turning operations. When a great many duplicate parts are to be machined, special tool equipment can often be used to advantage, but as the form of this equipment depends upon the character of the work, only standard tools have been shown in this illustration. The tool shown at A is a right-hand, roughing tool, and a left-hand tool of the same type is shown at B. Tool C is an offset or bent, left-hand round nose for roughing, and D is a right-hand offset roughing tool. A straight round nose is shown at E. Tool F has a flat, broad cutting edge and is used for finishing. Left-and right-hand finishing tools of the offset type are shown at G and H, respectively. Tool I has a square end and is used for cutting grooves. Right-and left-hand parting tools are shown at J and K, and tool L is a form frequently used for rounding corners.
Fig. 8. Diagrams Illustrating Use of Different Forms of Tools
The diagrams in [Fig. 8] show, in a general way, how each of the tools illustrated in [Fig. 7] are used, and corresponding tools are marked by the same reference letters in both of these illustrations. The right-and left-hand roughing tools A and B are especially adapted for taking deep roughing cuts. One feeds away from the center of the table, or to the right (when held in the right-hand tool-block) and the other tool is ground to feed in the opposite direction. Ordinarily, when turning plain flat surfaces, the cut is started at the outside and the tool feeds toward the center, as at B, although it is sometimes more convenient to feed in the opposite direction, as at A, especially when there is a rim or other projecting part at the outside edge. The tool shown at A could also be used for turning cylindrical surfaces, by clamping it in a horizontal position across the bottom of the tool-block. The feeding movement would then be downward or at right-angles to the work table.
The offset round-nose tools C and D are for turning exterior or interior cylinder surfaces. The shank of this tool is clamped in the tool-block in a vertical position and as the bent end extends below the tool-block, it can be fed down close to a shoulder. The straight type shown at E is commonly used for turning steel or iron, and when the point is drawn out narrower, it is also used for brass, although the front is then ground without slope. Tool F is for light finishing cuts and broad feeds. The amount of feed per revolution of the work should always be less than the width of the cutting edge as otherwise ridges will be left on the turned surface. The offset tools G and H are for finishing exterior and interior cylindrical surfaces. These tools also have both vertical and horizontal cutting edges and are sometimes used for first finishing a cylindrical and then a horizontal surface, or vice versa. Tool I is adapted to such work as cutting packing-ring grooves in engine pistons, forming square or rectangular grooves, and similar work. The parting tools J and K can also be used for forming narrow grooves or for cutting off rings, etc. The sketch K ([Fig. 8]) indicates how a tool of this kind might be used for squaring a corner under a shoulder. Tool L is frequently used on boring mills for rounding the corners of flywheel rims, in order to give them a more finished appearance. It has two cutting edges so that either side can be used as when rounding the inner and outer corners of a rim.
The turning tools of a vertical boring mill are similar, in many respects, to those used in a lathe, although the shanks of the former are shorter and more stocky than those of lathe tools. The cutting edges of some of the tools also differ somewhat in form, but the principles which govern the grinding of lathe and boring mill tools are identical, and those who are not familiar with tool grinding are referred to [Chapter II], in which this subject is treated.