With the launch of a versatile new chip-breaker, Chesterfield-based Dormer Pramet (www.dor merpramet.com) aims to increase the accuracy of indexable hole-making. Suitable for machining low-carbon and soft stainless steels, the SD (soft drilling) geometry is compatible with Dormer Pramet’s SCET and XPET drill ranges.

The SD chip-breaker has been specifically designed to provide improved stability and productivity when drilling low-strength soft and long-chipping material, where the balance of forces between the inserts becomes more difficult to maintain. The chip-breaker’s positive geometry with ‘stabiliser’ provides reliable chip evacuation, minimal vibration and low cutting forces, resulting in a quieter and more-stable machining process.

Dormer Pramet’s existing UD (universal drilling) geometry is suitable for machining most medium- and high-strength steels, while grades D8345, D8330 and D9335 provide a number of options for the company’s 800D line of 2D-5D indexable drills.

Marcel Nunes, product manager for indexable hole-making, says: “A key requirement for any indexable drilling task is accurate hole tolerance and straightness. This is best achieved when the cutting forces on the inner and outer inserts are balanced.

"However, the cutting conditions for both inserts are typically very different. The outer insert cuts smoothly at maximum speed, while the inner insert has to work closer to zero cutting speed, shearing rather than cutting and enduring higher impact forces.

"When this imbalance gets too large, the drill can be deflected off course, resulting in greater vibration and poor hole quality, unreliable chip evacuation and reduced tool life. When machining low-strength soft materials, long-chipping steel and stainless steel, the balance of forces becomes even more difficult to maintain. Our new SD chip-breaker has been specifically designed to provide better stability and productivity when drilling these materials.”

A video of these tools can be seen on Dormer Pramet’s YouTube channel (www.youtube.com dormerpramet).