Reducing job set-up times is key to saving money when machining, particularly if the work repeats regularly. Switching from the hard jaws needed for a first operation (op 1) to soft jaws for a second operation (op 2) requires removing them, cleaning the serrated interface, bolting on the soft jaws, inserting the boring ring and skimming the jaws. All of these tasks take time, during which the spindle is not turning and production is at a standstill.
Instead, 1st MTA’s quick-change process relies on three soft jaws (machined for securing a specific component) remaining attached to their respective base jaw counterparts. Sets of these assemblies can be tightened and released quickly using a manual key, allowing them to slide in and out of a chuck with minimal delay. The solution also ensures that runout is kept within 10 micron of the original TIR.
As an illustration of the possible monetary savings, 1st MTA has prepared a cost comparison that shows return on investment in a very short time. The comparison is based on the use of a Kitagawa QJR chuck, which is available in four sizes (7, 8, 10 and 12”) and uses the same jaws as standard chucks in the range. Moreover, the interface matches those of other manufacturers, while the bore is identical to that of the large bore chucks in Kitagawa’s BB range.
1st MTA’s hypothetical illustration is based on the use of a QJR10, a 254 mm quick change, three-jaw, through-hole power chuck with five sets of standard metric quick-change jaws plus soft jaws, which costs £6,124. This chuck interchanges directly with a Kitagawa BB 210 large bore chuck, priced at £2,177, featuring of jaws, with which the comparison is made.
The average time saved when exchanging the QJR chuck instead of the BB chuck is 15 minutes. Based on three set-ups per day and an estimated machining cost of £60 per hour, the daily cost saving for the three changeovers is £45. The difference in purchase price between the two chucks is £3,947. At £45 saving per day, the time required to break even is slightly less than 88 days. On this basis, the total saving by the end of the first year is £12,478, after which the annual saving is £16,425.
Apart from the significant financial advantage, 1st MTA points out that secure, high-quality workholding is an essential facet of cost-effective turning and can enhance a lathe's performance, whereas poor retention of a workpiece can reduce output, lower quality and compromise safety.
