Production engineers are no longer faced with the dilemma of choosing between tapping and thread-milling when machining large threads (24-48mm), now that Bromsgrove-based Walter GB Ltd (www.walter-tools.com) has introduced its T2711 and T2712 indexable-insert thread mills; these have reaches of 2.0 and 2.5x nominal diameter respectively.

While tapping large threads is quicker than thread milling, high tool costs and ‘bird’s nest’ swarf are the traditional ‘penalties’.

However, Walter’s T2711 and T2712 thread mills are said to compete with the productivity of taps on large threads. In a test involving the production of a 70mm-deep M36 thread on a wind-turbine component, the tools reduced costs by 45% and cut machining time by a fifth.

In addition, tool life was 540 parts per cutting edge with Walter’s T2711, compared to 300 parts using a competitor tool.

Designed for use on all materials in the ISO material groups P, M, K, S and H (up to 55HRc), the tools can be used for threads with a pitch range of 1.5 to 6mm, or 18-4TPI.

These tools have multiple cutting rows and an adjustable coolant supply with selectable radial or axial coolant outlets; moreover, the inserts each have three cutting edges featuring a soft-cutting geometry and a special chip-breaker.

With duplicated cutting rows, multiple thread sections can be machined simultaneously, achieving machining times comparable to those associated with thread tapping and forming.