Общий каталог Tungaloy 2020 - 2021 - страница 1630

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Parts for ToolsTechnicalReference Finishing stock 0.1~0.2 User’s Guide - Technical Reference Fundamentals of screw threads ᭹Relationship between lead, lead angle and pitch Thread angle Pitch P (large) Thread height Pitch P (small) = lead 1. Lead is the axial distance a screw advances in one rotation. In single start screw, the lead is equal to the pitch. 2. The inclination angle of a threaded groove is called lead angle. In screws of the same diameter, the lead angle increases as the pitch increases. 3. The side face of a completed thread groove is called flank. The distance Lead angle between the crest and the root is called thread height. Flank (large) Lead angle (small) ᭹Single and multi start thread 1. The single start thread has a single groove. Two start thread or three Lead start thread has two grooves or three grooves respectively. Two start thread Pitch 2. The pitch of multi start thread is the distance of adjoining groove. 3. When viewing the section of the multi start thread, the pitch is same as that of the single start thread. The lead of the two or three start thread is twice or three times the pitch. The multi start thread is mainly used for trapezoidal threads. ᭹Tolerance class of threads Tolerance classes of screw threads are expressed as follows: cutting or rolling, are generally used. 5H- and 4h-class Metric coarse external thread: 6h, 6g Metric coarse internal threads (former JIS first class) are generally finished by thread: 5H, 6H grinding. These classes are ranked with tolerances of thread diameter, For example, M8-6g means metric coarse external thread of pitch, thread angle, etc. For fastening applications, 6H- and 6g tolerance class. 6g-class (former JIS second class) threads, manufactured by TAC threading insert ᭹Difference between full-profile and partial-profile insert Full-profile insert In the full-profile insert, the major diameter of the thread is thread as shown in Figure below, these portions must be finished by the profiled finishing edge as shown in Figure below. finished by another tool later. Therefore, about 0.1 mm of finishing stock must be left on the Full-profile insert could produce no burr and good thread by the outer surface of the workpiece before threading. In trapezoidal profiled finishing edge. threads, since slants of 15º to 30º are left on the crest of the Partial-profile insert Full-profile insert ᭹ When machining trapezoidal threads: Trapezoidal thread Thread Thread Thread height Partial-profileinsertCrest (finished Surface turnedin precedingin precedingoperation)operationFull-profileinsertCrest (finished15° ~ 30°with threadinginsert) Portion to befinished later Partial-profile insert For example Partial-profile inserts can not be used for finishing of the Designation Pitch (mm)crest, but can be applied to a wide range of pitches.TPIInsert radiusRE (mm) 16ERA60 0.5 ~ 1.5 48 ~ 16 0.06 16ERG60 1.75 ~ 3 14 ~ 8 0.22 Corner radii of inserts are fitted to the thread of the smallest pitch. ᭹Difference between external and internal use inserts In full-profile inserts for metric and unified threads, the corner radius and thread height differ from those for the external and internal use insert respectively. Therefore, the right hand insert for external use and the left hand insert for internal use are not the same tool. Since the rake angles of toolholders are -10º for external toolholders and -15º for internal toolholders, the external / internal toolholders can not be used for machining internal / external thread. In Whitworth thread, though the external thread and internal thread have the same thread form, the external and internal toolholders are incompatible because of the different rake angle. For example Designation Applicable Insert radius R Thread hight Rake angle ofinsertsRE (mm)(mm)holders 16ER20ISO External 0.25 1.52 -10° 16IL20ISO Internal 0.14 1.3 -15° L042 www.tungaloy.com