threading WALTER PROTOTYP Application information UNJ thread form Inch screw threads UNJ profile Controlled root radius with increased minor diam

threading WALTER PROTOTYP Application information UNJ thread form Inch screw threads UNJ profile. Controlled root radius with increased minor diameter. The UNJ thread standard (ASME B1.15) defines a system of threads for highly stressed applications requiring fatigue strength. It was derived from a military specification (MIL-S-8879) originally published in December 1965. MIL-S-8879 was primarily thought of and used for aerospace fastener and threaded component applications. Due to the increase in both its use and types'of applications, the AmericanSociety of Mechanical Engineers developed and published ASME b1.15 in 1995. Form UNJ screw threads are of the same form as Unified Screw Threads to ASME/ANSI B1.1 except External threads The root has a maximum and minimum prescribed continuous radius, and is not merely rounded due to tool wear. Internal threads The minor diameter is increased to accommodate the maximum root radius of the external thread. There is no radius requirement for either the crest or the root of the internal thread. Please see pages D 465 D 466 for proper "J" thread tap drill size. Use of Unified Tooling. Many of the UNJ thread form characteristics are the same as for UN threads. Therefore, some of the tooling used to produced one form can be used to produce the other. External UNJ threads must be produced with a prescribed root radius therefore, standard unified screw thread (UN) tooling may not be used. Internal UNJ threads are not required to have a root radius therefore, ground-thread taps designed to produce unified screw threads of the proper class of fit may be used. The letter "J" need not to be marked on the tap. The larger product minor diameter of the UNJ internal thread requires the use of a larger tap drill than is used when producing unified screw threads. For those manufacturers that require a radius, PROTOTYP offers a UNJC and a UNJF tap with the radius see page D 198 for UNJC and page D 223 for UNJF. Designation UNJ product threads are identified by the letter "J" in the thread symbol, and a thread class symbol including an "A" for external threads or a "B" for internal threads. D 447 Technical information