Process re-engineering carried out by Chessington-based Mollart Engineering (www.mollart.com) at a UK automotive plant has extended tool life when drilling oil feed holes on forged steel crankshafts by over 40% — and allowed drill feed rates to be increased from 180 to 500mm/min, cutting production times dramatically.

Achieved following extensive production trials and product process approval, the improvement in gun-drilling was based on the latest Botek Typ 113-HP gun drill for producing 5.3mm-diameter holes x 100mm deep in the pins of crankshafts.

Part of the supply contract negotiated by Mollart’s tooling director Chris Barker, is the on-going provision of a re-grinding and coating service for these tools, which are used under round-the-clock production conditions.

Mr Barker said: “The change in gun-drilling technology that we have introduced has generated massive savings — plus the added security and predictability of a process with known tool life and spindle up-time. We are now working with the customer’s engineers to extend the use of these HP drills to other applications.”

The Typ 113-HP drill has a special nose grind, highly polished flutes and a kidney-shaped coolant channel that ensures maximum evacuation of chips from the cutting zone.

Moreover, these drills are suitable for use over a wide range of materials, from aluminiums to high-strength steels. The two-spindle special-purpose gun-drilling machine used for this application is being run at 4,200rev/min, and neat oil passes through the drill at a pressure of 70 bar.