Coating increases hob life by a third

Citation

(2009), "Coating increases hob life by a third", Aircraft Engineering and Aerospace Technology, Vol. 81 No. 3. https://doi.org/10.1108/aeat.2009.12781cad.009

Coating increases hob life by a third

Article Type: Materials From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 81, Issue 3

A new generation of multi-layer coating has been developed by LMT that, it claims, will enable the operating life of gear hobs, under dry cutting conditions, to be increased by up to a third over cutters that use more conventional nitride coatings (Figure 1).

The Nanosphere coating, which is under patent application and available on gear hobs from LMT (UK) of Coventry, can be applied to high-speed steel as well as carbide cutters. It not only insulates the tool like a heat shield but also reacts “elastically” to protect the hob teeth from the high thermal and mechanical stresses generated during the gear nobbing process.

The coating was developed over some 10 months by a joint team from LMT’s Fette and Boehlerit divisions, using the LMT’s in-house physical and chemical vapour deposition laboratories and production facilities.

Figure 1 A new generation Nanosphere multi-layer coating from LMT (UK) enables life of gear hobs to be increased by up to a third under dry cutting conditions

The new coating claims a distinct advantage over normal nitride coatings where, according to LMT, the arduous cutting operation can lead to the so-called “eggshell” effect where, under high temperatures, the single hard surface of the coating cracks and separates from the softer substrate of the tool. It then tends to flake back in similar vein to an eggshell which leads to a dramatic reduction in the cutting life of the tool.

LMT’s engineers describe how the 4 μm thick Nanosphere multilayer coating surrounds the tool like a “layer of rubber.” This has the effect of slowing down any thermal reaction during the gear cutting process between the materials being cut, the chip and the hob’s teeth, thus extending the time taken for the substrate to heat up. At the same time, the elasticity of the multi-layer coating enables it to move with the substrate and so overcome any influence from loss of stability in the cutter created by the process.

Details available from: LMT (UK) Limited, Tel.: +44 (0) 2476 369770, Fax: +44 (0) 2476 369771, web site: www.LMT-tools.com