Mitsubishi Materials boosts indexable insert drill performance
1 min read
Difficulties such as chip clogging on deep holes, dissimilar rates of wear on inner and outer inserts due to differing peripheral speeds, plus flexing and wear of the drill body itself have all been resolved with a new and innovative design for Mitsubishi Materials' MVX high performance indexable insert drill.
The outer insert in this type of drill naturally runs at a higher speed than the inner, leading to higher levels of wear. Consequently, the inner insert needs to have a higher level of stability and resistance to fracturing at lower speeds. This has been negated by using a CVD coated outer insert that has higher abrasion resistance, in tandem with a PVD coated inner insert that can cope better with fracturing forces and resistance to welding. This combination means improved reliability and fewer changes of insert for increased levels of productivity.
The SOMX-type inserts are interchangeable from inner to outer position, have four cutting edges and a unique wavy chipbreaker design for improved chip control. The peripheral edge also has a wiper type geometry for excellent hole wall accuracy and surface finishes. The inserts are also positioned in such a way that when cutting, they are both equally in contact with the workpiece, thereby reducing drill body flex to provide a more consistent performance.
A new CVD-coated grade MC1020 is suitable for placing on the outer cutting edge. It displays high wear and plastic deformation resistance, allowing it to be effective when used for machining steels and stainless steels.
For cast iron drilling, a different CVD grade, MC5020, is used for the outer insert. Excellent abrasion and thermal cracking resistance makes it ideal for cast and nodular cast irons.
The inner insert uses a VP15TF grade, with a PVD coating based on the well-known Miracle type. VP15TF has a broad spectrum of desirable properties such as a micro-grain substrate for strength and an excellent resistance to chip welding. These all-round properties also allow it to be used as a replacement of the outer insert when conditions become unsuitable for a CVD coated insert.
The tool body is designed with through coolant holes and an optimum sweep of the flutes that provide extra metal thickness behind the direction of the principal cutting force. This controls tool body deflection and helps to achieve reliable deep hole drilling up to 6xD. Additionally, the body surface is heat treated to prevent wear from chip evacuation. The sizes available are 17 -33 mm diameter and in L/D=2, 3, 4, 5 and up to L/D=6.
