When Target Sports bought its first Citizen B12 Type V, CNC sliding headstock lathe, it wanted to machine high quality brass dart bodies. But, so successful was the installation, saving some 10 secs on a previous 26 sec cycle, that it was quickly followed by a second machine which the company found the combined output from the pair was equivalent to that of eight single spindle cam-driven automatics. Based on the success of this venture, the company's management were inspired to diversify into production of precision turned parts in separate premises in Hertfordshire.

The company now also operates a Citizen B12 Type VI and a Citizen M12 in addition to the original pair of machines bought from NC Engineering in Watford.

'The B12 Type Vs are fitted with a backspindle capability which completely finish machines the dart bodies in a single set-up whereas bodies made on the cam autos required second operations to put in the hole for the point,' explained Target managing director Garry Plummer.

'Because of the second operation, the aggregated time for cam auto produced bodies was around 26 seconds whereas the Citizen's, are able to provide a complete job with superior finish some 10 seconds faster.

In addition, the B12s can run unmanned or with minimal attendance so direct labour costs are very low,' he explains.

Target Precision of Hoddesdon was set up in 1997, following a management buy-out of the company from its original owner.

By then, technical director Chris Thorburn had been on board for two years.

He brought with him a wide range of general turned component manufacturing experience, which has subsequently proved invaluable as the company started to diversify.

He says: 'The B12 Type V's provided us with a straightforward introduction to CNC sliding head machining so that, by the time Target Precision was established, we were fairly comfortable with the machines.

Initially we looked to fill spare capacity on these machines as dart production tends to be a seasonal business and unlike cam autos they also prove very useful as 'jobbing' machines.

They are relatively easy to set, while the ability to check and optimise programs via the electronic handwheel, means our setters are confident to get the machines running very quickly.' Target Precision operates on a minimal price structure rather than a minimum order quantity, with the added guarantee of quick turn-around.

The normal smallest batch tends to be around 1,000 parts with a considerable amount of work sourced from the electrical and electronics sectors for which typical components include connector pins and sockets.

Connector work tends to be based on small diameter bar between 2.5 mm and 4 mm covering materials such as copper alloys, beryllium copper, and some stainless steel.

Target's next purchase was the more sophisticated Citizen M12, which is more of a mill turn centre, followed by the B12 Type VI, bought at NC Engineering's 2000 Open House.

Both of these machines provide C-axis positioning for cross drilling and milling while the M12 offers much higher flexibility being able to accommodate up to 80 tools on the turret alone.

It also has the ability to overlap cutting routines, which is proving a valuable time saver on more complicated jobs.

The M-Series machines were needed to accommodate the increasingly complicated jobs being processed such as an ever higher proportion of connector pin sockets.

These parts required slotting and the drilling of vent holes while other components demanded the milling of various flats.

'Arguably we could have got away with a Citizen L-Series machine rather than the M12,' Garry Plummer confided, 'however, one of our key selling points is our ability to respond and here the M12 seemed to be the more appropriate choice to put before our customers.

In reality, the machine specification gives us capability to do virtually anything.

While there are certain parts that are quicker to process on the B12 type VI, once more complex tasks are involved, then the M12 really comes into its own,' he explains.

One military specification connector is a prime illustration.

The component required drilling, counter-boring followed by a hole drilled through the centre.

A flat had to be milled on the outside diameter and the Y-axis feed of the turret used to position for centring and drilling an off-set hole.

The part was then picked-up by the sub-spindle and parted-off, after which the back end was centre drilled and a slitting saw used for producing cruciform slots prior to a special tool finishing the tines.

'The machines are accurate, reliable and capable of very high metal removal rates,' remarked Chris Thorburn.

'On a B12 we achieve 2.5mm depth of cut at a feed rate of 0.03mm/rev while running at up to 3,000 revs/min.

Accuracy is similarly impressive; we expect to maintain 15 microns as a matter of course while hole diameters can be held to 10 microns.' Reliability has also been very good, especially considering our objective of running the machines round-the-clock wherever possible.

Garry Plummer concluded: 'When we have needed service it has been very good.

But when we check our records, the total maintenance cost for our first B12 over a five year period has been about GBP500.

This is almost negligible when compared to the machine's earnings in that time.'