18 Machinery Market +44 (0)20 8460 4224 17 February 2011

Safe and secure set-upsManufacturer of work-holding solutions establishes a reputation for turn-key specials

I t is not unusual for ThameEngineering Co Ltd to receive an urgent call from

someone who has not givenwork-holding sufficient priorityand is now confronted by amajor problem.

With a history dating back to 1946 and nowtrading as Thame Workholding, the Aylesbury-based company (Tel: 01844 208050 —www.thameworkholding.com) says it has the experience and the products to solve virtually any work-holding challenge. Itmanufactures the world’s largest and mostdiverse range of soft jaws for machinechucks and vices, plus it offers a widechoice of other work-holding products and systems. It also has a long-establishedreputation for the design and manufactureof complete turn-key ‘specials’.

Technical director David Handleysays: “Not every request for help is alast-minute panic call. People do come tous saying ‘I have this machining capability,and I need to machine this component;what is the best way to do this?’ We mayeven be asked to recommend a more suit-able machine tool. Being asked for advice— and it will be impartial advice, becausewe do not favour any particular machine tool

manufacturer or supplier — means we have an early opportunity to influence machining decisions. This enables us to offer the most efficient and cost-effective work-holding solution.”

One example of how this approach hasworked in practice is Thame’s ‘magic chuck’,which was designed specifically for twin-opposed spindle turning machines dedicated to the machining of plastic inserts for prosthetichip replacements. The ‘magic’ nickname is cour-

tesy of a US-based medical-products companythat had been struggling to machine a double-axis profile to the necessary degree of accuracyand surface finish.

Additional axis

Thame’s answer to this particular challengewas a vacuum chuck (mounted in the secondspindle) that can be tilted as it revolves, therebyproviding the second axis and allowing the use

Thame’s ‘magic chuck’ for machining prosthetic inserts

As well as work-holding equipment,Thame markets automation systems

HEAD ONE, COLLET CHUCK

of single-point tooling to machine the specifiedsurface finish. The sequence begins with feedingthe bar stock through a collet chuck to a stopand then machining external features that in-clude a convex profile.

The opposing vacuum chuck is then advancedto a synchronised position where its concaveprofile mates with the pre-machined externalfeatures; vacuum pressure is applied and part-ing-off takes place. The second spindle head allows for the turning and milling of all featuresthat can be accessed on the zero axis, before thepivot mechanism is activated. Milling and turn-ing of all accessible features on the tilted axisthen takes place. When machining, deburringand part number engraving have all been com-pleted, the vacuum is released and low air pres-sure ejects the component into the parts catcher.

‘Magic chuck’

Initially designed to tilt to 15deg and subse-quently to 20deg, Thame has now designed a‘magic chuck’ — currently at the pre-productionstage — that will tilt through any angle. Thislevel of complexity explains why the companyspreads its expertise across such a wide range of products, with commodity items such as softjaws providing a financial counterbalance to theuncertainties involved in the design, develop-ment and production of prototypes and specials.

Mr Handley says: “With a standard product,you can be sure — based on past experience —that it will do exactly what it is supposed to doand that there is a regular and on-going demand;but with ‘specials’, the demand is variable, andwe can never be absolutely sure that it will workuntil we try it out.

That is one very good reason for having an in-house manufacturing capability; and becausewe have been running a night shift for the past20 years, if we do encounter a problem with a ‘special’, we can usually modify the designovernight and, in effect, get the time back — if not necessarily the additional cost!”

Thame’s origins lie in tool making, and it was while working for the nearby Morris Motorsplant that the company began supplying softjaws. From there it was a short step to supply-ing soft jaws designed specifically for thechucks fitted to the Colchester, Harrison andHerbert manual lathes that dominated UK andoverseas markets at that time. Moreover, despiteglobal competition, Thame continues to exportaround 30% of its manufacturing output.

Sales director Maurice Day says: “Work-holding is our forte, and our customers deal directly with qualified engineers who can givethem advice on the best possible work-holdingoption. That said, we have to be prepared todemonstrate that our solution will do the job.”

The ISO 9001-accredited 10,000ft2 factory is kept busy machining a wide range of com-ponents, from chuck and vice jaws to modular fixturing systems for co-ordinate measuring machines, special chucks and fixtures, and‘cubes’ for vertical and horizontal machiningcentres. The clamping of workpieces may bemechanical, hydraulic, pneumatic or vacuum to suit the application. Thame can even supply‘ice chucks’ to hold components that are tooporous, small or irregularly shaped to be secured in any other way.

“We are constantly modifying our designs and improving our manufacturing processes,”says Mr Handley, “and we are in the fortunateposition of being able to test our designs in aworking environment. Specials are usually allocated to the six vertical machining centresequipped with the Lang zero-point system — for which we are the UK distributor — becauseset-ups are quick, flexible and better suited toone-offs and small batch runs. However, theworkshop also houses six horizontal machiningcentres, along with other machine tools.”

Thame does factor certain innovative work-holding products, such as the Lang clampingsystem, which is based on patented ‘form closure technology’. This requires just 3mm of clamping depth on a square or rectangular

workpiece to provide maximum holding powerat minimum clamping force. The advantages ofthis method of fixturing include material savingsdue to minimal wastage; fast set-up; and unre-stricted access for five-face machining, therebyfacilitating the use of short cutting tools.

A specific pattern of indentations is stampedinto two opposite sides of a workpiece, and thestamped workpiece can then be positioned (and,if required, re-positioned to an accuracy of +/-0.02 mm) in a Makro Grip centre vice, the jawsof which have a matching pattern of holdingteeth. The Makro Grip vice is equipped withprecision clamping studs for precise zero-pointlocation on a 27 mm-deep Quick Point pallet.

Automation

As well as being a stand-alone clampingprocess used on three- and five-axis milling ma-chines, this process can be automated using thegravity-powered Lang modular automation sys-tem, which puts automatic pallet loading and un-loading within reach of everyone using a verticalor horizontal machining centre. Pallets are trans-ferred via an integral vertical elevator into aspace-saving Eco Tower magazine that can store up to 120 Quick Point pallets.

Stored pallets slide down the Eco Tower’s spiral chute under gravity and are transferred(as required) to the designated machine tool byan Eco Feed handling unit. The low pneumaticdrive forces involved impose a minimum re-quirement in terms of housing, enclosure orother form of man/machine safety barrier. Thismeans there are fewer restrictions on the opera-tor’s freedom to access the working area aroundthe machine tool, while running on a single-phase electrical supply and a 6-bar air supplymakes installation fast and simple.

In conclusion, Mr Handley says: “Every daybrings new challenges, and these are a constantreminder that work-holding is every bit as im-portant as selecting the right machine tool andcutting tools.”

Safe and secure set-ups

20 Machinery Market +44 (0)20 8460 4224 17 February 2011

One of Thame’s special features