Общий каталог Yamawa 2022 - 2023 - страница 1167

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Description of productsTechnical Information Classes of Internal Threads and Classes of Taps P class Pitch Basic Pitch Dia. Sizes SP JIS class 2 HT,PO class 2 HT,SP JIS class 2 PO class 2 4. Standard Class and Oversize The standard class of the tap which we have been manufacturing for general use is JIS 2nd class. This JIS 2nd class is basically de ned as the thread limit of the tap which can cut the internal thread of old JIS 2nd class. With technical innovation such as various tap classi cation, high precision tapping machines, workpiece materials and diversity of workpieces' dimension, conventional products having JIS 2nd class could not always satisfy customers’ requirement due to following situations. (1) In cutting taps, the shape of utes in uences the thrust of axial direction. We explain about oversize cutting tendency caused by the thrust force of axial direction by referring to that of Straight uted hand taps as a basic. Spiral pointed taps have little tendency of oversize cutting, but Spiral uted taps have a tendency of oversize cutting. (2) Due to the relation between pitch diameter of JIS 2nd class tap and that of GO thread plug gauge for the internal thread of old JIS 2nd class, if the cutting edge of tap wears normally, threads cut by the tap will become gauge out quickly resulting in short tool life. (3) Due to the material or shape of workpiece, the material can shrink. In these cases, it would be better to use oversized taps to compensate for shrinkage after tapping. (4) When plating is to be applied to internal threads after threading, we should use oversized taps to compensate for the thickness amount of plating. (5) Where little tendency of oversize cutting is expected, but large wear in tools is expected during tapping operation, it is better to consider using oversized taps as much as possible. From these situations, in spiral pointed taps, spiral uted taps and various types of special purpose taps, YAMAWA has adopted the P class limit system which is explained in previous pages. Depending on the type and designation of taps, YAMAWA has selected from the P class system the tap's thread limit which the tap manufacturer recommends for general tapping operation. From the reason of (1) stated above, even in the same tap designation, the recommendation for spiral pointed taps is di erent from that for spiral uted taps. Especially in the standard products of spiral pointed taps and spiral uted taps, YAMAWA has speci ed the recommendation di erently in the relation to oversize cutting tendency. Oversize taps mean the taps of which thread limits are oversize above the recommendation. This is due to the reasons (3), (4) and (5) stated above. Usually for oversize taps, YAMAWA recommends the taps which thread tolerance classes are one or two steps above the standard recommendation. As you can see in the picture drawn in previous pages, the recommendation can be used for cutting JIS (ISO) 6H internal threads. Technical-16