Diamond coated parabolic drill breakthrough for composite machining

Citation

(2008), "Diamond coated parabolic drill breakthrough for composite machining", Aircraft Engineering and Aerospace Technology, Vol. 80 No. 5. https://doi.org/10.1108/aeat.2008.12780ead.017

Diamond coated parabolic drill breakthrough for composite machining

Article Type: Equipment and software From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 80, Issue 5

A diamond-coated parabolic drill has been developed by the Onsrud division of LMT Fette suitable for drilling both carbon fibre and carbon graphite materials. The new drill reportedly overcomes typical problems associated with delaminating, flaking, splintering and whiskering, caused by the highly abrasive nature of the material. The design of the drill is said to also reduce thrust forces, gives more manageable chip formation, improved centring and faster penetration rates.

Available through LMT (UK) of Coventry, the profile of the Parabolic Flute Form Drill improves chip flow, swarf evacuation and resistance to wear and abrasion through a combination of tool geometry and the multi-layer nano-crystalline, six micron thick diamond coating.

The drill has a 30 per cent web thickness, as against conventional 12-15 per cent, adding both strength and rigidity. Under cutting conditions the flute redistributes mass to the outer cross-sectional area of the tool’s construction and due to the greater helix angle of 36 to 40°, instead of the normal 28 to 32° as standard tools, a significant increase in the shearing action of the cut is achieved.

The drill point is a “modified” split point with a positive rake at its apex that has the advantage of reducing the thrust under cut. According to LMT centring is also improved, penetration rates can be increased with better chip formation and evacuation from the cutting zone aided by the lower coefficient of friction (0.15-0.2) of the 6 μm smooth diamond coating.

Cutting trials are reported to have demonstrated an ideal speed of 75 m/min to maintain the best surface finish on both carbon fibre and carbon graphite materials with feed rates of 0.075 mm/rev applied.

Details available from: LMT (UK) Limited, Tel: 02476369770, Fax: 02476369771, web site: www.LMT-tools.com