191 Каталог KYOCERA 2016 Твердосплавный вращающийся режущий инструмент ENG Стр.189

Catalog KYOCERA 2016 Solid carbide cutting tools Стр. 189 0191 ENG Lab2u

TAPS ENGINEERING DATA (continued) TERMS definitions DEFINITION OF TERMS APPLYING TO TAPS (cont.) PITCH DIAMETER On a straight thread, the pitch diameter is the diameter of the imaginary co-axial cylinder...the surface of which would pass through the thread profiles at such points as to make the width of the groove equal to one-half of the basic pitch. On a perfect thread this occurs at the point where the widths of the thread and groove are equal. On a taper thread, the pitch diameter at a given position on the thread axis is the diameter of the pitch cone at that position. RAKE The angular relationship of the straight cutting face of a tooth with respect to a radial line through the crest of the tooth at the cutting edge. Positive rake means that the crest of the cutting face is angularly ahead of the balance of the cutting face of the tooth. Negative rake means that the crest of the cutting face is angularly behind the balance of the cutting face of the tooth. Zero rake means that the cutting face is directly on a radial line. RELIEF (or Thread Relief) The removal of metal from behind the cutting edge to provide clearance and reduce friction between the part being threaded and the threaded land. ROOT The bottom surface joining the sides of two adjacent threads, and is identical with or immediately adjacent to the cylinder or cone from which the thread projects. SPIRAL FLUTE A flute with uniform axial lead in a spiral path around the axis of a tap. SPIRAL POINT The angular fluting in the cutting face of the land at the chamfered end; formed at an angle with respect to the tap axis of opposite hand to that of rotation. Its length is usually greater than the chamfer length and its angle with respect to the tap axis is usually made great enough to direct the chips ahead of the taps cutting action. STRAIGHT FLUTE A flute that forms a cutting edge lying in an axial plane. TOLERANCE In producing a tap to given specifications, tolerance is: (a.) the total permissible variation of a size; (b.) the difference between the limits of size. CHAMFERS FOR THREAD CUTTING TAPS The tap chamfer is the tapering of the threads to distribute cutting action over several teeth. The type of hole to be tapped has much to do with the chamfer style of that tap that’s best suited. Some holes go all the way through; some, while not through-holes, are relatively deep; some are quite shallow (a little deeper than diameter). Each of these three kinds of holes -through, deep-bottoming blind, and shallow bottoming - has a tap chamfer best suited to threading requirements. TAPER TAPS This style, with a 7-10 thread chamfer, has the longest chamfer of the three to distribute action over the maximum number of teeth; and the taper also acts as a guide in starting the cutting action in the hole. Taper style taps start the thread square with the workpiece. Taper taps are commonly used in through holes and in materials where a tapered guide is necessary. PLUG TAPS This style, with a 3-5 thread chamfer, is most widely used in through holes and where there is sufficient room at the bottom in blind holes. SEMI (or Modified) BOTTOMING TAPS This style, with a 2 to 2.5 thread chamfer, should be used whenever possible in difficult material applications in blind holes, when threads are not required to the bottom of the hole. ,-AAAAAAAAAAAAAAAAAAAAJ BOTTOMING TAPS This style, designed with a 1 to 2 thread chamfer, is made with just enough chamfer for starting in the hole; as the name implies, it is designed to thread blind holes to the bottom. NOTE: Taper, plug and bottoming taps as a set, in a given size (for example: 1/4-20 NC) are identical as to size, length and vital measurements; the difference is in the chamfered threaded portion at the point. As a rule, such taps when used by and are furnished in sets of three of a given size... namely, taper, plug and bottoming (and should be used in that order). Kyocera 189