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 the hard jaws, cleaning the serrated interface, bolting on the soft jaws, inserting the boring ring and skimming the jaws.

This all takes time, during which the spindle is not turning.

Salisbury-based 1st Machine Tool Accessories (www.1stmta.com), a supplier of work-holding equipment, says that a quick-change chuck can eliminate most of this wasted time, cutting the delay between the end of op 1 and the beginning of op 2 by as much as 90%.

Instead of wasting 20min, changeover typically takes just 2min.

The 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. This solution also ensures that run-out is kept within 10µm of the original TIR (total indicator reading).

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.

This is based on the use of a 254mm Kitagawa QJ10 three-jaw, large-through-hole power chuck with five sets of standard metric quick-change jaws plus soft jaws, which all costs £6,124.

It replaced a Kitagawa BB 210 large-bore chuck, priced at £2,177 with five sets of jaws, with which the comparison is
made.

The average time saved when exchanging the QJR chuck instead of the BB chuck is 15min. Based on three set-ups per day and an estimated machining cost of £60 per hr, the daily cost saving for the three changeovers is £45.

The difference in purchase price between the two chucks is £3,947.

Calculated on a £45 saving per day, the time required to break even is slightly less than 88 days, and 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 work-holding is essential for cost-effective turning and can enhance a lathe’s performance, whereas poor retention of a workpiece can reduce output and quality — and compromise safety.