Режущие и зажимные инструменты Hoffmann Group 2026 - страница 255

GBP 57 Core hole drilling – important component of a thread. Core hole drilling is not just part of a thread, it also enormously influences the thread machining process and the service life of the thread-cutting tool. Taps and fluteless taps can only work reliably if certain important rules are adhered to during the preparatory work stage. Core hole diameter / Straightness length Key criteria for the core hole for thread generation to good process reliability Roundness Surface Tolerance situation Taps/fluteless taps Thread mill The tolerance band of a tap or fluteless tap is significantly narrower than the The tolerance of the thread mill has no effect on the tolerance situation of the permissible tolerance range of the finished thread. thread to be produced. The required tolerance is governed by the machine tool The tolerance is designed so that a correct thread is generated from the start. The and is generated by a circular movement of the tool. Tool wear can be tool wears in service and eventually reaches the point where the correct thread compensated by programming. profile can no longer be produced: The thread is now smaller than the lower tolerance of the “Go” gauge. The tolerance for the tap or fluteless tap could then be positioned at the upper 13 part of the internal thread area. Here there is, however, the risk of producing an oversized thread which is above the upper limit of the “No Go” gauge. Taps or fluteless taps with “X” tolerance used on materials that have no problem with oversize are positioned higher in the tolerance zone. The result is longer tool life as a result of higher wear tolerance. Schematic diagram of common metric production tolerances Permissible effective diameter tolerance range of the internal thread. Tolerance range 7GX Permitted effective diameter tolerance range of a 6GX 7G tap/fluteless tap made to DIN EN standard. ISO1 ISO2 6HX ISO3 6G 7G 4H 6H 6G 4HX 6H Permissible effective diameter tolerance range of a 4H tap/fluteless tap produced to the Factory standard. 0-line 255