Almost 78 years after Tenable Screw was founded by a Swiss watchmaker as a manufacturer of screws, the company has become one of the UK’s largest subcontract producers of turned parts.
With three manufacturing sites in Marlborough, Coventry and its headquarters in Wimbledon, Tenable has more than 250 machine tools that include 71 coil-fed Escomatics, 26 multi-spindle machines, 56 sliding-head turning centres and four fixed-head turning centres. The machines produce millions of components every month.

Committed to an ongoing culture of quality-assured engineering, Tenable Screw invests 10% of annual turnover in the latest technology to support its live base of over 250 customers. Part of this investment strategy has seen the arrival of a Tornos MultiSwiss 6X14.
The modern face of Tenable Screw sees the company manufacture everything from connector pins and sockets through to bolts, screws and much more for the electronics, instrumentation and control, automotive, aerospace, medical, defence, transport and telecommunications sectors in quantities that range from prototypes and small batch production up to runs of more than 100,000. With London property at a premium and the 45,000 sq ft Wimbledon headquarters packed with machine tools, the philosophy behind the MultiSwiss 6X14 purchase was to add flexibility and capacity to a business with limited floor space.
Commenting upon the arrival of the Tornos MultiSwiss 6X14, Tenable Screw commercial director Nigel Schlaefli says: “We initially acquired the MultiSwiss to alleviate capacity issues on our single-spindle sliding-head machines, while having the production capacity of multiple single-spindle machines in a floor area significantly smaller than five-to-six single-spindle machines. Although we initially used the MultiSwiss as a flexible centre that was supporting our single-spindle machines, like any subcontract manufacturer that has a fluid workflow, customer base and component types, the MultiSwiss is now dedicated to producing just one component family. Despite being restricted to a single family of parts, the productivity, precision, cost reduction and floor area benefits are evident.”
Just a few months after installing the MultiSwiss 6X14, Tenable Screw won a long-term automotive contract. The family of parts comprises stainless-steel pins that require numerous external turning processes, as well as knurling, drilling and parting off. The UK contract demands 1,500,000 parts every year, a quantity equal to 30,000 parts per week. Tenable Screw trialled the automotive part on one of its sliding-head turning centres and the cycle time was 1.5 parts per minute. In stark contrast, the MultiSwiss 6X14 was capable of producing 9 parts per minute – an output equal to six sliding-head turning centres.
“We calculated that we would have needed to run six single-spindle turning centres for 24 hours a day to meet the contract capacity level,” says Schlaefli. “In comparison, the MultiSwiss 6X14 hits the same output by just running for 17-18 hours a day. This means we can run the machine during a day shift, change tools and re-stock the barfeed at the end of the shift, and then run for an extra 8-9 hours unmanned.

As with all manufacturers with relentless quality standards, Tenable Screw has a dedicated quality control department and its production adheres to ISO9001. With regard to production, Tenable applies SPC and CPK procedures to its manufacturing processes. The CNC manager responsible for more than 60 CNC machine tools at Tenable Screw, Paul Kelley, says: “If we were producing this automotive part on six machines there would inevitably be a variation in CPK values between them. Although the part has an average tolerance band of ±20 µm, the MultiSwiss easily maintains a band of less than ±10 µm, and this improves our CPK and SPC values considerably.
“What we have also found is that each spindle on the MultiSwiss works independently, unlike conventional multi-spindle or CAM-auto machines. This allows us to change the spindle speeds for each spindle and operation, which in turn considerably improves surface finishes and contributes to extended tool life compared with other production machines.”
Contributing to both quality and tool life is the hydrostatic spindle technology integrated into the Tornos MultiSwiss 6X14.
“Over an extended period of time, roller bearing technology on machine tools will generate wear and this results in diminishing component quality,” explains Kelley. “However, the hydrostatic spindle technology on the Tornos eliminates wear; this means precision and consistency will not reduce. The hydrostatic spindle also eliminates vibration in the spindle head and this enhances component quality and surface finishes.”
Referring to the tool life on the machine, Kelley says: “The MultiSwiss will run for two days without any need for tool changes. Even then, we are only changing inserts as a precautionary measure. The only tool we change on a daily basis is the knurling tool. To put this in context, we are producing 18,000 stainless steel parts before we change inserts. The MultiSwiss is achieving at least double the tool life of the single-spindle machines.”
The MultiSwiss at Tenable Screw has demonstrated how it can lower floor-space requirements and reduce power consumption, tooling and general running costs compared with five or six single-spindle machine tools offering a similar production output.

Concluding upon the CNC control and ease-of-use characteristics of the MultiSwiss, Kelley says: “The MultiSwiss has 14 linear axes and seven C axes with up to 18 tool stations. Despite the number of axes and tool positions, the machine is significantly easier to program than single-spindle sliding-head machines. We apply G-code programming and determine the number of operations for each spindle. Combining these features with a well-lit and easy-to-access work envelope, the MultiSwiss is easier and faster to set-up than single-spindle machines.
“This ease-of-programming is certainly beneficial; but one equally important factor is the operator,” he adds. “There is a distinct lack of skilled CNC machine operators and programmers in the UK. Combining the ease-of-use characteristics with the facility to be as productive as six alternate machines, the MultiSwiss reduces the reliance and requirement for highly-skilled staff.”
For further information www.tornos.com

R&M Assembly, part of the R&M Electrical Group, has over 20 years’ experience in the assembly, modification and distribution of specialist power distribution and control systems for use in hazardous (explosive) environments.

The company supplies a diverse range of customers across the oil and gas, nuclear, rail and marine sectors, to list but a few. A major advantage of R&M Assembly is its ability to provide bespoke systems in short lead times. This brings its own challenges as the company must overcome production bottlenecks caused by some manufacturing processes. Investment in new machining capacity has not only overcome these bottlenecks, but enabled R&M Assembly to generate new business from existing and new customers.
“Our business model is a reactive one in which we have to respond quickly to demand from our suppliers and customers,” says R&M Assembly division manager Martin Goodall. “One of our main tasks, therefore, is to iron out peaks and troughs in production to deliver a managed service and, where possible, avoid any unexpected issues. The limited machining that we have to do is one of those areas, as on a major project we may have over 2000 holes to drill and tap, and we can only do that at a certain speed with our existing equipment. The option to outsource this work was considered, but the loss of control over deliveries and quality saw us look to expand our in-house capability.”
In order to justify the investment in new machining capacity, Goodall had to identify efficiencies through in-depth time and motion studies, and with limited machining experience he called on XYZ for assistance in the form of area sales manager Keith Ellis. The initial thought for Ellis was to double-up on an existing XYZ SMX 2500 bed mill as the control was familiar and easy to use. However, talking through the needs of R&M Assembly, it became clear that to achieve the necessary versatility and productivity, a machine with a tool changer and fourth-axis unit would bring greater benefits.
“If we had gone with another SMX we wouldn’t have required any training and so it would have made our life easier initially, but in conversation with Keith it became obvious that a step-up was required and the new XYZ 500 LR vertical machining centre would have a significant impact on how we do business,” explains Goodall.

R&M Assembly’s projections, based on a major customer project valued at £1m, suggested that the addition of the XYZ 500 LR would generate savings of up to six weeks in labour, or £64,000, based on which the machine would have a payback period of just 16 weeks.
“Our projections also indicated that the addition of the tool changer would allow much greater unmanned operation, freeing-up operator time every day by as much as 6.5 hours, during which they could be doing other tasks,” says Goodall.
These projected savings were enough to justify investment in the machine, however, they must then be delivered upon. By maximising the capability and capacity of the XYZ 500 LR, with its 13 kW, 8000 rpm spindle, 12-position tool carousel and 510 x 400 x 450 mm of axis travel, combined with the agility of the linear rail technology on all axes, an immediate positive impact on efficiency was seen. Typically, a batch of 200 electrical junction boxes would take 2-3 weeks to produce, with drilling and tapping multiple holes being the bottleneck. Now, by utilising the XYZ 500 LR, machining is completed in two days and the batch fully processed within a week. Machining efficiency has seen gains of up to tenfold by reinventing the processes to match the machine’s capabilities.
The benefits of investing in new machining capacity for the R&M Electrical Group go beyond simple cycle-time savings and efficiencies; the machine is being used as a sales tool to drive new business for the group and typical of this is its partnership with Hawke International, a manufacturer of cable glands and electrical enclosures.
“With investment in the XYZ machine, Hawke has recognised our commitment and is supporting us as an extension to their manufacturing capability, allowing us to gain EAC certification, which will differentiate us from our competitors – all from buying an XYZ machine tool,” says Goodall. “The investment in the machine, along with our relocation to new premises, has allowed us to review many processes and techniques. This is seen as a sign of confidence, especially for customers servicing the oil and gas sector, which is coming out of its downturn.”

The XYZ 500 LR is part of the recently introduced range of linear rail machining centres from XYZ Machine Tools. LR series machines make use of the latest developments in linear rail technology, while providing a cost-effective entry into the world of vertical machining centres, says the company. These machines provide a natural progression or complementary solution for customers moving from manual or XYZ ProtoTrak-controlled machines. The LR range is in addition to XYZ’s recently extend HD range of vertical machining centres, which continue to make use of the box slideway construction, offering greater capability and capacity when required.
For further information www.xyzmachinetools.com

In engineering, a lot of focus is centred on complex systems and assemblies. Every manufacturer has a signature approach, or systems that help to define a brand. However, from a logistics point of view, every component is of equal importance. A shortage of a single, small bolt over an entire assembly can cause a production shutdown. Optimas, a global industrial distributor and service provider of C-class components, employs fastener experts on the ground at its partner manufacturing facilities to combat this issue.

“The first step of any fastener relationship must be to gain familiarity with the customer’s operations,” states Ian Larkin, customer application engineer at Optimas. “Past experience in an industry can be important here, but leading manufacturers will enact varying approaches to achieve a finished product, so gauging specific customer requirements is important. Hence the advantage of having a fastener expert on the ground. In contrast, someone operating off site would not be able to reach the level of understanding required to accurately address specific fastener issues.
“As a fastener partner, we have to fit an ‘ideal standard’,”
he continues. “We are working with big global customers who are driven to succeed, so we have to respect current processes and enhance the component policy to the specific requirements of the manufacturer.”
The easiest way to gauge these requirements is during a line walk. An Optimas expert will travel the entire production line looking at points of use, while asking basic questions to see what can be tweaked or possibly improved. This way, the expert can meet key figures on the line, while also taking a focused approach to tackling fastener problems on the ground.
“We don’t want to tear up the customer’s rulebook, but if we can point out a cost saving or alternative option to production staff, we will do so,” says Larkin.
A good example of the benefits this strategy can provide to manufacturers is highlighted by one particular Optimas customer in the US.
“We noticed a washer was being added to a flange screw even though it wasn’t particularly necessary,” says Larkin. “These washers were identified at multiple points of use, so we posed the question to the assembly team. It turned out that during the design of the product, the head engineer had requested the inclusion of washers to improve the aesthetic of the overall product. We were able to demonstrate that the washers were unnecessary for the application, and as a result, delivered an annual cost saving of $30,000.
“You can utilise engineering expertise as part of a sales function, but it also adds value to our customers. By making sure that we don’t make presumptions, we start an open relationship with the customer in close proximity. This builds trust and lessens the impact of implementing new methodologies. By getting involved with the product and seeing how it is used, people on the ground can get a deeper insight into possible solutions.”

Another customer application engineer at Optimas, Gerry Abraham, adds: “A key aspect of integrating with a manufacturer’s operations is responsiveness. Such businesses work to exacting timeframes in all aspects of their work, whether full scale production or prototyping a new product. Fastener suppliers who simply supply components can leave manufacturers with the impression that if a component problem arises, they alone must solve the issue. Optimas aims to differentiate itself by working together with purchasing, design and engineering teams to aid problem solving.
Abraham says that one project comes to mind, which was in relation to design engineering activity for a new diesel engine. A bolted joint for the turbo mounting was backing off during testing. As a result, the turbo itself was coming loose, producing excessive noise in operation. The manufacturer approached Optimas for a solution.
“We connected the customer with a number of suppliers to help rethink the situation. The customer trialled three or four recommended locking-type fasteners to replace the problem part, before selecting a preferred option. Ultimately, we wanted to give the customer choice and a chance to improve performance, so they could be confident in the part going forward.”
Another key element in providing an integrated approach is cross-departmental communication, as engineering program manager Chris Sterner, points out: “By starting this dialogue from the beginning, efficiency and response is improved. In addition, close contact means that specific fastener solutions can be enacted across multiple projects. Open dialogue regarding each other’s projects allows wider implementation of identified solutions, instead of starting from scratch every time a potential problem arises. By standardising solutions, you also deliver cost and efficiency benefits.”
Consistent presence is clearly important for these customers. Optimas tries to breed familiarity by being present at design reviews, which is a lot more beneficial to the manufacturer than simply being on the end of a phone. It also allows Optimas to share solutions, as each fastener problem solved allows the company to convince these varied groups within a business that it can be trusted to deliver.
“Providing guidance on fasteners affects the activities of the purchasing, design, engineering and assembly teams – so being able to balance the requirements of each of these groups is paramount,” says Sterner. “Regular face-to-face contact is the optimum method, helping to build relationships between teams and delivering a fast response. Ultimately, a fastener expert must communicate across each department to achieve the perfect balance.”
Becoming a fully integrated fastener expert means taking the emphasis on component knowledge away from the manufacturer. Manufacturers therefore are not required to brush up on standard parts, availability, material standards or overall usage – enabling time to be spent on other areas of the business.
“One story really fits this philosophy,” says Sterner. “An Optimas expert was asked to demonstrate some fasteners that were mentioned during a customer meeting. As he didn’t have these samples readily available at the meeting, he took pictures of the fasteners that were installed on his own car. He even took out a number of fasteners from the vehicle so he could share samples with the customer and demonstrate their usage. While quite an extreme approach, it was certainly effective in demonstrating the solution to the customer.

“The capabilities of the service also go a long way,” he continues. “Our access to failure mode analysis and full technical studies means we can provide exact answers to tackle fastener application issues. If we don’t have an answer ready for the customer immediately, this capability means we can react as fast as possible with a high technical proficiency. If it’s a unique problem, as fastener experts we can also learn from similar experiences, so the benefits of shared knowledge are also available.”
Fasteners are the only assets on a production line that are used uniformly, but with engineering typically focusing on landmark innovations, the emphasis upon them can be diminished. As a fastener expert, challenging this preconception is all part of the job.
“Fasteners may be the most inexpensive components that a manufacturer utilises on a production line, but they are one of the most critical,” concludes Sterner. “A lack of fasteners will shut down production just as much as complicated components, so we must demonstrate to our customers that the expertise we deliver can provide reliable service, no matter the challenge.”
For further information https://global.optimas.com

Two more twin-pallet, horizontal machining centres (HMCs) from Heller have been installed at the Booth Drive, Wellingborough factory of Mahle Powertrain, an independent company specialising in the design, development, test and manufacture of combustion engines. A four-axis Heller H2000 has joined two identical models in an eight-machine production line dedicated to manufacturing cylinder blocks, while a larger five-axis FP6000 has been added to expand the capabilities of a flexible machining cell.

At the end of 2016, Mahle’s project manager Geoff Brown, production engineer Bob Price and others decided that the decade-old line producing aluminium engine blocks for a major British OEM needed to be upgraded. The line comprises six HMCs each performing separate operations plus two bore-honing machines positioned at the end. All HMCs were originally supplied by a Japanese manufacturer, but in early 2017 the first two machines in the line were replaced with UK-built Heller H2000s.
“We were already familiar with Heller machines, as we operated 21 of them very successfully for more than a decade at our facility in nearby Ryle Drive,” explains Brown. “They were used for manufacturing cylinder heads and blocks for a British off-road machinery manufacturer, although that contract has now ended and the machines have been sold. I also had experience of working with Heller horizontal machining centres at another engine manufacturer that operated more than 20 of them in a transfer line.
“We sent some V8 cylinder blocks to Heller’s Redditch technical centre, where they carried out Op 10 and Op 20 trials on an H2000, which is ideally sized for the work,” he continues. “Op 20 was particularly successful as, with the addition of new fixtures, it overcame a problem we were having in machining a side port in the new cylinder block model currently in production.”
As a result of the successful trials, the first two machines in the production line at Booth Drive were replaced with Hellers, and the benefits were immediately noticeable.

“The cycle time for each of the first two operations is one-third faster on the new machines: eight minutes instead of the previous 12,” says Price. “Impressively, the 33% time reductions have been achieved despite including some sections of the Op 40 cycle into Op 10, and parts of Op 30 into Op 20.”
The raised productivity is largely down to the rigidity of the H2000s, the higher speed (16,000 rpm) spindles with HSK63A interface and programmable through-coolant up to 70 bar, all of which support faster cutting feed rates. Rapid traverse is quicker than before, and further time savings derive from integral hydraulics for automatically clamping the engine blocks, along with air detect for checking that the component is seated correctly. A probe in the tool magazine for identifying broken cutters further reduces time by removing that function from the cycles.
Brown points out that all these features are fitted as a matter of course to the Hellers, whereas many other machine manufacturers class them as extras, increasing both cost and delivery lead-time. The offer of generously equipped, standard machines, with the enhanced back-up that their manufacture in the UK promised, was a significant factor in Mahle’s choice of the H2000s. So also was the efficient swarf management, essential to removing large amounts of aluminium chips efficiently from the machining area and avoiding hours of costly machine stoppage.
No-scan/no-run safety software is run through the Siemens control to prevent a component from being machined unless its barcode has been scanned. Linked into Mahle’s new SAP ERP system, which became operational at the start of 2018, the data provides traceability to ensure stock accuracy.

Capex approval to replace the third HMC was given by the Mahle board in mid-2017, and another Heller H2000 was ordered. Built in Redditch and commissioned at the beginning of this year, it took over Op 30 from its predecessor during February 2018. Again, the previous 12-minute cycle has been cut to eight minutes, despite taking some of the load from Op 50. When the fourth H2000 assumes responsibility for Op 40, it will carry out some of the Op 60 cutting scheme in addition to delivering a more efficient Op 40 routine. By then, the TAKT time for the whole line will be 10 minutes. Performing Ops 50 and 60 on Hellers in the future will lower it further to eight minutes.
Another ongoing project at the Booth Drive facility is the reorganisation of the shop floor so that all six HMCs and the two bore-honing machines are in a straight line, as at present some zig-zagging is involved. This configuration will allow two operators to be deployed on other work, one from Ops 50 and 60, and one from the honing section, helping to amortise the capex more quickly. The overhead gantry is being extended and reconfigured so that the existing Dalmec equipment can be retained for handling the 45 kg aluminium blocks in and out of the machines.
A further notable advantage of the rearrangement will be to slash work-in-progress to two or three components, whereas at present there are sometimes as many as 100 queuing on the shop floor. The beneficial consequences will include major savings in tied-up capital, reduced double handling, minimal risk of damage and less space occupied on the shop floor.
The line currently operates 24 hours a day, five days a week, saving overtime compared with when it ran 24/7 due to a previously longer TAKT time. Tight tolerances are held, including 50 to 70 µm on true position of some features and 10 to 12 µm on holes up to 16 mm diameter. Prior to honing, each cylinder bore and crank bore is pre-machined to 28 µm roundness, 0.15 mm true position and 50 µm squareness.
In another development elsewhere in the factory, at the start of this year a Heller FP6000 five-axis HMC built in Germany was added to a pre-existing flexible machining line that already comprised a vertical machining centre and three HMCs of a different make; all five-axis models. During a recent open day at the Wellingborough factory, it was explained that the line has been relaunched as a facility for the manufacture of heads and blocks, as well as a wide range of other prismatic parts, from one-offs to runs of up to 20,000, for customers in any industry.
For further information www.heller.biz

As the inventor of the hydrodynamic bearing more than 100 years ago, Michell Bearings has spent the last century constantly developing its product range to meet the ever-changing needs of the company’s global customer base. The use of the latest production technology, decades of in-depth experience and the application of stringent quality systems, has resulted in the South Shields-based company gaining an impressive reputation in bearing design and manufacture for both the industrial and marine engineering sectors.

As the efficiency, reliability and longevity of any bearing depends largely on the quality of the methods used in its manufacture, Michell Bearings employs a wide range of CNC machine tools and advanced production aids.
The recent installation of a Hermle C60 UMT five-axis CNC machining centre prompted Chris Kemp, Michell Bearings’ manufacturing engineering manager to contact Tony Lewis of Thame Workholding with the intention of exploring ideas that would enable the company’s new acquisition to maximise its potential.
“As a designer and manufacturer of self-contained white-metal bearings and PTFE-faced hydrodynamic bearings, our products can be found in a range of challenging applications throughout the world,” states Kemp. “We have a long history of manufacturing bearings that withstand the test of time, and have products installed with 35 of the world’s navies on more than 300 vessels. Meticulous production and inspection methods ensure the quality of our bearings and help safeguard the global standing of the company.
“In accordance with our ongoing quest to enhance the company’s capabilities and further increase production efficiencies, we recently purchased a Hermle C60 UMT five-axis CNC machining centre with a capacity of 1200 x 1300 x 900 mm in the X, Y and Z axes. Our new machine tool allows the dynamic processing of workpieces up to 2000 kg in weight.”
With the aim of achieving the highest possible yield and looking to guarantee that the machine consistently met the demanding standards of precision at Michell Bearings, Kemp recently contacted Tony Lewis of Thame Workholding.

“After studying our new machine’s specification and capabilities, while also considering our objectives, we concluded that a work-holding arrangement, incorporating Thame Workholding’s Lang QuickPoint system and Samchully jaw boxes, would be ideal for our needs,” says Kemp. “By working together, Tony and I developed a system incorporating Thame Workholding’s products that has considerably reduced our new machine tool’s set-up and job change-over times, while greatly increasing its production availability. In addition to boosting efficiency, our new work-holding system’s ability to securely grip workpieces helps us to guarantee that the required levels of accuracy and surface finish are achieved on
a consistent basis.”
The work-holding arrangement conceived by Lewis and Kemp consists of several circular ‘slave’ plates that can be set-up offline. These slave plates have Lang QuickPoint studs attached to their bases and a series of QuickPoint plates that remain loaded on the machine table. The slave plates also feature T-slots that allow Samchully jaw boxes to be moved into position, tightened on to the workpiece, then centralised ready for machine loading.
On completion of a machining routine, the slave plate holding the finished part can be removed by crane, after which the next slave plate holding the new workpiece can be lowered into position. Upon quickly securing the new slave plate to the machine’s table, the next machining operation can begin.
The Hermle CNC machining centre’s spindle is able to move clear of the table, a useful capability that ensures the working area is completely unrestricted and accessible. As a result, completely unhindered crane loading is possible from directly above the machine table’s centreline.
According to Thame, the Lang QuickPoint system provides precise and repeatable mounting of fixtures and other elements on to machine tables, indexers, cubes, rotary tables and mill-turn machine tools. QuickPoint’s height of only 27 mm makes it the lowest profile zero-point-system currently available, says the company. Manual clamping is achieved with just one tightening screw (hydraulic or pneumatic clamping is also possible). The use of this simple and sturdy system allows a maximum pull-down force of 6000 kg.

“The QuickPoint location system is based on four wedge bolts in the pallet that engage with four grooved locating bolts screwed to the vice or fixture,” explains Lewis. “The highly repeatable nature of QuickPoint guarantees that Michelle Bearings’ slave plates can be loaded with workpieces off-machine, then quickly and precisely attached to the Hermle machining centre’s table. Now, rather than wasting valuable time setting-up a workpiece when the machine is idle, then performing machining operations as subsequent activities, these processes are capable of being completed concurrently within the machine’s cycle time. Deploying this strategy can help deliver outstanding machining efficiencies.”

For further information:
www.thameworkholding.com
www.michellbearings.com