WNT bespoke tooling helps Bendalls Engineering complete mission critical parts

Carlisle, Cumbria-based Bendalls Engineering has an impressive track record as a manufacturer of pressure vessels and specialist steel fabrications. Machining is a relatively new dimension to the business following the acquisition by its parent the Carrs Group of Clive Walton Engineering, whose machine shop was relocated at Bendalls in 2012. Clive Walton had been a long-term customer of WNT and that relationship also transferred with WNT’s Matt Darbyshire continuing to provide sales and technical support to Bendalls.

While well known for its extensive range of standard cutting tool products, WNT also has a dedicated team designing and developing stooling for special applications. Therefore, when Bendalls Engineering won a contract to manufacture a series of venturi-type pumps that would be used to test highly radioactive, high pH, ‘liquor’ found in the nuclear industry, WNT was more than happy to become involved in meeting the requirements for this challenging work.

Key features on these pumps that needed to be machined, to high dimensional and surface finish tolerances included a series of relatively small diameter bores, with high diameter to length ratios. Machining features such as these was unknown territory for the precision engineering team at Bendalls, a situation complicated by a lack of high pressure coolant on the available CNC lathes combined with the 316 stainless steel material. “We looked through the standard tooling catalogue, but could find nothing suitable for our requirements, so we called Matt in and gave him copies of the drawings and set him the initial challenge of just giving us the confidence that WNT could design and manufacture the special tools needed,” says Stuart McCubbin, Bendalls Engineering’s Machining Engineer. “Unfazed by the project, Matt and his colleagues at WNT quickly returned with a full proposal and tool drawings that gave us the confidence to proceed.”

With multiple drills, tapered boring bars and reamers involved, and not one tool being standard, Matt made himself available for the initial complex cutting trials. Such was the difficulty of the machining that one feature took a full day to machine. Further complexity was added by the limitations of the lathe’s z-axis, which was used to its maximum to accommodate the tools that measured up to 312 mm in length (and only 15.3 mm in diameter in some cases). Due to these lengths, and the requirement for a good surface finish, the tools were manufactured from solid carbide, with WNT’s MiniCut inserts with 0.2 mm corner rads being fitted to the boring bars.

“This was a learning curve for us and there was an element of trial and error, changing insert corner rads, for example, to achieve the surface finish we wanted, but we all worked together and we achieved the results we wanted with the help of WNT’s and Matt’s involvement, which included being there at the machine throughout the initial cutting trials,” says Peter Norman, Bendalls’s Machine Shop Foreman. Part of that process included thinking outside of the box using grades, particularly drilling, that wouldn’t normally be the first choice. On some of the WNT Quattro-style drills a steel grade of carbide was the only available option, it shouldn’t have worked, but it did, thanks to the team pulling together with ideas, including taking the coolant concentration up to 12 per cent to aid lubrication.

Due to the nature of the project and its end-use, documentation of the whole process was important for both the machined parts and the final welded assembly. “When the machined parts are welded they have to maintain very tight (in welding terms) concentricity and alignment. This pushed the welding techniques to new limits,” says Ian Willacy, Precision Engineer at Bendalls. “All of the parts and assemblies had to be photographed using a £30,000 bore camera such was the importance of the tolerances and surface finish throughout the length of these long bores.”

“While our standard catalogue contains over 56,000 product lines it can’t always provide a solution to a customer’s specific requirement. Our investment in design and manufacture for special tooling such as those implemented at Bendalls Engineering is testament to the commitment that the Ceratizit Group makes to providing a cost-effective and practical solution to meeting the needs of customers. We then back up that design and manufacture with the support at the machine to ensure everything runs as smoothly as possible,” says Tony Pennington, Managing Director, Ceratizit UK & Ireland.