Study on High-Speed Roughing Methods of Large Size Screw Thread of High Speed Steel Material

摘要

The most popular tools for generating the gears are hobs, whose materials are the High Speed Steel (HSS) in the many case. Because the HSS contains such the rare components as W, Mo, Co and V, the material cost is expensive. A sequence for manufacturing the hobs consists of (1) hob-thread roughing, (2) flute milling (3) normalizing the body, (4) backing-off hob thread, (5) quenching and tempering and (6) grinding. Thus the sequence is very complicated and the machinability of HSS also is very poor due to the alloy elements above mentioned. Therefore the manufacture cost is higher too. In this paper the cost-down methods are developed in rough threading the large-sized hobs and the availability of these methods are checked by exprimenting with two typical end mills on the backing-off lathe. In order to decrease the rough machining times, the above operations (1) and (4) among the above operations are simultaneously worked on the backing-off lathe. Thus, in case of module 20 hob, the rough threading and backing time 33 hours required in the ordinary way can be shortened up to 24 hours. Through these results, it is cleared that the threading in backing with the tapered surfy end mill is hopeful for decreasing the manufacture prices.