Diamond and boron nitride tools - joke Technology GmbH - #6

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303 3 �¨ �¨ �¨ Tel. +49 (0) 22 04 / 8 39-0 • Fax +49 (0) 22 04 / 8 39-61 • info@joke.de 3. Diamond and boron nitride tools Diamant- und CBN Special tools Embedding depth of grits The embedding depth is one of the essential elements to be observed during tool manufacture and has a direct effect on the properties and service life of the tool. Depending on the application, the embedding depth must be designed differently in order to achieve both optimum finish (required surface quality) and guarantee optimum economy during tool use (long service life). Tool design An optimum coating is a basic prerequisite for tool quality. In order to guarantee this, a number of different factors should be taken into account as early as the tool design stage: 1. Sharp edges and points in the coating area are unfavourable and should preferably be avoided. The corner radius of sharp-edged tools will be at least 1.5 x grit size. This yields for example: Required grit size 126 micron 126 x 1.5 = 0.19 mm 0.19 mm indicates the required minimum radius in this case. 2. Narrow penetrations, such as grooves, slots and deep profiles are very difficult or almost impossible to coat, since the irradiation of the galvanic process corresponds to an approximate 90° angle. Reliable results are obtained by divided tools. Favourable chip flow Particularly tools for plastic and rubber machining should have a good chip flow because of the large volume of chippings that accumulate in order to prevent overheating and clogging of the tools. Segmented coatings, bores, slots or grooves assist the chip flow and simultaneously achieve a cooling effect. In the case of larger, cylindrical tools, a spirally applied sectional coating yields a uniform cut without chatter. An additional, beneficial effect – the costs for coating and recoating are reduced. In order to reduce the coating surfaces, the tool is preferably to be provided with V-shaped grooves, e.g. with a thread cutting chisel. Depending on the wall thickness of the carrier, 0.2 – 1.5 mm. Mminimum radius R 0.19 mm inadvisable �¨ good max. galvanic irradiation depth �¨ not advisable divided = good 90 °