Drill is diamond-coated to machine composites

LMT Fette has introduced a diamond coated parabolic drill to overcome delaminating, flaking, splintering and whiskering, when drilling machine carbon fibre and carbon graphite materials.

The Onsrud division of LMT Fette has deveoped a diamond coated parabolic drill for drilling carbon fibre and carbon graphite materials.

LMT said that the drill overcomes delaminating, flaking, splintering and whiskering, caused by the highly abrasive nature of the material.

The design of the drill also reduces thrust forces and gives more manageable chip formation to improve centring and achieve faster penetration rates.

The profile of the Parabolic Flute Form Drill improves chip flow, swarf evacuation and resistance to wear and abrasion.

It uses a combination of tool geometry and the multi-layer nano-crystalline, six micron thick diamond coating to do this.

LMT (UK) in Coventry told manufacturingtalk that the drill has a 30% web thickness, when compared with conventional 12 to 15% web thickness, and so adds strength and rigidity.

Under cutting conditions the flute redistributes mass to the outer cross-sectional area of the tool's construction.

Also, the greater helix angle of 36 to 40 deg (instead of the normal 28 to 32 deg on standard drills), significant increases the shearing action of the drill's cutting action.

* Modified drill point - the drill point is a 'modified' split point with a positive rake at its apex.

LMT said it has the advantage of reducing the thrust under cut.

Centring is also improved, so penetration rates can be increased with better chip formation and evacuation from the cutting zone.

Cutting is also aided by the lower coefficient of friction (0.15 to 0.2) of the 6 micron thick, smooth diamond coating.

LMT said that cutting trials have demonstrated an ideal speed of 75m/min to maintain the best surface finish when drilling carbon fibre and carbon graphite materials.

Feed rates used are 0.075mm/rev.

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