The parts in question are aluminium, with 226 of them produced by machining a 30 mm thick plate, leaving parts attached to the base for further operations. Key among those is the generation of three identical internal M3 fine threads to a depth of 8.0 mm.
DW Engineering was employing conventional machine tapping tools, but there were several shortcomings, as the company’s managing director, David Watt, explains: “The tapping process was quite slow, and it is also the case that the life of the available taps, at around 200 finished holes per tap, was insufficient for us to complete a full machining table load of 226 components/778 threaded holes, without need for time-consuming replacement of the tapping tools.”
In practice there were additional problems, such as unclean threads and occasional tap breakages, which required constant monitoring, making unmanned machining impossible.
Horn’s DCG three-tooth thread milling system provided the solution. Says Watt: “We tried a few alternatives before we became aware of the Horn DCG system. Initially we had reservations, based on the apparent delicacy of the tooling, its cost and our unfamiliarity of thread milling on such small features. In practice, we were quickly convinced of its worth.”
All of the company’s requirements were achieved, following introduction of the Horn DCG solution. As well as a single three-edged DCG tool able to complete multiple ‘batches’ of threads, a single batch can now be machined in six hours, marking a reduction of five hours, while quality and cleanliness levels achieved now mean scrap has been eliminated.Concludes Watt: “A further big gain is in process reliability, as it is now possible to carry out the threading process unmanned. Moreover, Horn thread milling tooling has subsequently found use on a number of other applications.”