High Speed Machining : Background

Possibly the first work of note on HSM was that of Salomon who ran a series of applied experiments from the period 1924 to 1931, when a German Patent was granted for this work. The Patent was founded upon a series of cutting speed curves plotted against machining temperatures for a range of materials (Fig. 214). In these tests Salomon achieved peripheral cutter speeds of 16,500 m min–1, utilising either fly-cutters – for chip morphology data, or helical milling cutters – notably when cutting aluminium. Salomon contended that the cutting temperature ‘peaked’ at a specific cutting speed, which he termed the ‘Supercritical speed’ , further, when the speed was increased still faster the temperature he noted, decreased. Moreover, either side of this ‘supercritical speed’ zone, it was suggested that ‘unworkable regimes’ occurred where the HSS cutters could not withstand the severe forces and temperatures generated. As mentioned, when the cutting speed increased beyond this ‘zone’ the temperature reduced to those expected by ‘normal data’ cutting conditions, permitting practical cutting operations to be carried out. The problem being with this early HSM work is that any theoretical rationale is not available and the experimental procedures are somewhat unclear, but Salomon can be considered the founder of ultra-high speed machining (UHSM) – taking cutting data beyond that considered in the so-called ‘Taylorequations’.

Effectively it can be established that there were four distinct periods of advancement in the field of UHSM, with the first one being from the early 1920’s to the late 1950’s, with each period during this time and thereafter, being separated by a significant event. Obviously during the first period, the work instigated by Salomon (i.e. in the 1920’s – alluded to above), was followed by the originally-commissioned United States Air Force (USAF) major research contract, being from 1958 to 1961. Previous to this contract award, little in the way of UHSM work in the preceding decades had occurred, apart from that in the States by Vaughn (1958). Vaughn, shortly became aware of the Salomon Patent, acquiring limited information on this work through the United States Consul in Berlin. Vaughn’s (Lockheed) group were also familiar with the many technical references concerning the ‘art’ of oil well tube perforation utilising perforated cutters, these ‘cutting actions’ being employed to perforate oil well casings at explosive speeds. Such background work, now meant that Vaughn had ‘set the scene’ for the second period of UHSM development.