When High Wycombe-based Hempstead and Johnson needed to replace an ageing CNC lathe a few years ago, it chose a Gildemeister CTX 500.

When High Wycombe-based Hempstead and Johnson needed to replace an ageing CNC lathe a few years ago, it chose a Gildemeister CTX 500. It met the all important physical requirement for one-metre between centres capacity and was available with powered tooling/C-axis capabilities, while the Manual Plus control system provided a high level of local manual programming capability. 'It has proved pound for pound certainly the best machine for the job,' recalls managing director Roy Langley, 'and its performance led us to buy two further CTX 400 lathes and two Deckel Maho machining centres - a 63V and a 103V.

We've developed a good relationship with DMG, to the extent that we rarely go elsewhere for a machine tool.

The variety of work that we do means that we place a high value on the flexibility and reliability which the DMG machines provide.' Hempstead and Johnson, which is ISO 9002 registered, began as a manufacturer of jigs and fixtures but has evolved into a more general high precision subcontractor.

It produces both discrete components and basic sub-assemblies; one of its key capabilities is the manufacture of components using ceramic for which it has specialist diamond grinding facilities; around 40 per cent of output has some ceramic content.

In addition the company is the UK agent for the Benz range of taper tooling, speeders and angle heads.

It shares its premises with an associated business, Special Drills and Cutters, which produces custom-manufactured drills and reamers.

'We have a lot of expertise and a high level of skills within the company,' says Mr Langley.

'That allows us to take on a very wide variety of work.

Most of our throughput currently relates to components for pneumatic equipment, as well as defence, automotive and aerospace-related work.

Batch quantities of 20-off are typical and most jobs include a significant amount of value added.

Though we supply customers on a just-in-time or kan ban basis we tend to manufacture economic batch quantities based on our own forecast of likely customer requirements.' Hempstead and Johnson regularly deals with cast iron mild and stainless steels, titanium, light alloy, plastics and ceramics.

General turning tolerance is +/-25 microns with six microns roundness and 10 microns flatness and squareness required on turning operations.

Milling capacity is available for up to 500mm cube while turning capacity for bar up to 75mm by 1000mm is available.

Although its turning machines are installed as chucking machines, bar work can be accommodated by supporting the material in the spindle tube and using a bar puller on the turret.

'The defining job when we bought our CTX 500 was a piston rod for a pneumatic cylinder which demanded a meter between centres and facilities for cross drilling and milling.' Mr Langley recalls.

'A lot of the turning work that we do - around 50 per cent - needs second operation capability for generation of end features or flats and cross holes so the availability of powered tooling on the machines keeps our production costs competitive.

Our latest turning machine, the CTX 400 Series 2 also has this facility.

One of the things that we like about the Gildemeister machines is that they have plenty of main spindle power.

As a result they can handle a very wide range of work, combining high metal removal rates with very good accuracy.' A similar line of reasoning led to installation of the two Deckel Maho machining centres, which were bought in successive years to replace existing older CNC machines.

David Lander, works manager, explains.

'On the DMU 103V in particular there is enough space on the table for multiple sets of fixtures so we can achieve a productivity advantage on jobs requiring more than one set-up.

We also like the Heidenhain CNC controls fitted to both machines; the conversational input is well thought out while the remote controller is a very useful feature for setting up; it means that the operator can remain closer to the job throughout.' A recent job completed on the DMU 63V was machining of a prototype air manifold from a solid billet of material as opposed to the more common cast route.

Successful completion of this type of work demonstrates both the capabilities of the machine and the engineering skills of Hempstead and Jonson's setter/programmer operators.

It also illustrates the savings available to OEMs in respect of flexibility, elimination of pattern making costs, foundry charges and shortened lead times.

Both the DMU 63V and the DMU 103V have 8000 rev/min spindles and 24-tool capacity tool changers.

Hempstead and Johnson has also used them with Benz spindle speeders - which can be interchanged from the tool magazine - to achieve up to 25000 rev/min for machining ceramic.

Depending on the hardness of the ceramic material the machines are used either to complete machining of specific features or to provide accurate spot locations for manual drilling.

Mr Langley concluded.

'We've been very happy with the performance and reliability of the equipment that we've purchased from DMG.

It has certainly helped to maintain our competitiveness over a period of years by maximising the amount of machining that we can complete in each set-up.'