When Leighton Buzzard-based BD Precision Engineers was presented with a machining challenge by a long-standing customer, it became apparent that the company’s reputation for meeting all deadlines would be under serious threat.
Due to the poor tool life and quality that the existing tooling was achieving, BD Precision risked the job going over deadline and budget.
However, with the assistance of Sheffield-based WNT (UK) Ltd (
www.wnt.com), which stepped in to offer alternative tools and technical support, the company’s reputation remained intact.
Over its 40-plus years, BD Precision Engineers has grown from a two-man business providing a manual milling capacity to become a modern precision sub-contractor with the latest CNC machining, assembly and inspection capabilities. Although its customer base is diverse, BD Precision Engineers found that most of the materials it was asked to machine revolved around aluminium, stainless steel and brass.
Therefore, when the company was asked to produce a batch of components in Inconel 718, it had to rely on the advice of its then preferred tooling supplier for cutting data.
BD Precision Engineers’ manager, Jed Juster, said: “We were advised to avoid carbide tools and run a pecking cycle with 0.5mm steps using a powder metal drill. The result was a cycle time of 11min to drill four holes in each component through 8mm of material. Moreover, each drill could only achieve five holes before it either broke or had to be replaced. The pecking was simply creating a work-hardened surface.”
These drilling problems were compounded by issues relating to profile-milling and face-milling the part — both operations that were generating lots of burrs and poor surface finish, plus an overall cycle time of 43min per part. This was simply unacceptable, as was the fact that the recommended end mill was only lasting for one component.
WNT technical sales engineer Duncan Slough changed the drill from a powder metal type to WNT’s solid-carbide WTX Ti drill with through coolant; this was held in a WNT Centro P collet chuck, which offers a guaranteed run-out of less than 3µm. The cutting data suggested was 55m/min and 0.08mm/rev with no pecking. As a result, the drilling cycle time for the four holes in each part was reduced to 40sec — plus the drill achieved 200 holes and looked as good as new when it had finished.
For profiling , WNT recommended a 10mm-diameter solid-carbide HPC Ti cutter running at a feed rate of 500mm/min — a 10-fold increase on what was being achieved before. Furthermore, the HPC Ti cutter machined 26 parts before needing to be changed, compared to just four parts with the original supplier’s cutter.
The final piece in the jigsaw was to use a 63mm-diameter indexable-insert face mill using WNT’s 5240 grade inserts to finish-mill the part and eliminate all the burr and surface finish problems.