It is not unusual for precision sub-contract machinists to be wary of disclosing details of contracts they are involved with — either one-off ‘special’ jobs or production schedules that stretch over the long term.

Sheffield-based Cosmopolitan Engineering, which has ISO 9001 accreditation, is a case in point; it continually secures contracts that include workpieces destined for high-profile manufacturing projects for a number of ‘blue chip’ clients throughout the UK.

Cosmopolitan makes a wide range of components — from precision one-offs for marksman’s guns to steam traction engine parts and nuclear project work.

Production manager Mark Leonard says: “We simply can’t talk about most of the jobs, which is a great shame, not least because the complexity of some of the final-build projects would really show how small highly skilled engineering companies such as ours continue to play a crucial role in creating awe-inspiring engineering spectacles that are the envy of the world.”

The lack of publicity surrounding such work often disguises the fact that the seven-employee company — established for more than 30 years and supplying parts of all sizes and in all metals (including tool steels and titanium) — has a variety of CNC machines, including four from Sheffield-based TW Ward CNC Machinery (www.wardcnc.com).

These are a trio of Hyundai-Wia turning machines — an L400LMC lathe with C axis and driven tools, an SKT-300 turning centre, and an L300C two-axis lathe — plus a Hartford Omnis 1020 vertical machining centre.

Many of the components produced on these machines are one-offs or produced in small batches (up to 10). That said, one particular on-going large contract is for the volume machining of a family of axles from EN24T billets.

The axles are made in three sizes: 100mm in diameter x 290mm long; 120mm in diameter ¥ 610 mm long, and 120mm in diameter x 937 mm long. All sizes are turned to diameter; on the shortest axle, a grease nipple hole is drilled, and a 16mm-wide x 20mm-deep cross slot is machined by the SKT-300.

On the two larger sizes, which are machined on the L400LMC (this has a 2m bed, a C axis and driven tools), a screw thread is also machined. The largest axle is then transferred to the Omnis VMC, which produces a 32mm-wide x 16mm-deep keyway that is 140mm long.

The axles, which are for a prestigious engineering project in London, are supplied to the customer ready for assembly.

Mr Leonard says: “We have been dealing with Ward CNC for many years, and we have become very familiar with the ranges of machines that the company holds in stock.

“The Hartford VMC was our first machine from Ward CNC, followed by the Hyundai-Wia SKT-300, the L300C and — most recently — the L400LMC. Importantly, all the Hyundai-Wias are powerful geared-headstock machines. There is a 22kW spindle motor on the L300C, 26kW on the SKT-300 and 30kW on the L400LMC.

“We’ve noted the reliability of each machine, so each time we needed to increase our CNC machining capacity, we knew there would be no concerns on machine quality or the back-up if we returned to Ward CNC.

“We ideally like to have one operator running two machines, so commonality of Fanuc CNC systems has also been a factor in our choice of machines.”