The new tool allows machine shops to produce chamfered holes in a single operation, thus reducing tool/insert cost per hole and/or machine cost per hole, while at the same time achieving extended tool life.
According to Sandvik Coromant, it is suitable for ISO P (steel) and ISO K (cast iron) materials. CoroDrill 870 is an exchangeable tip range that now offers an insert-based 45° chamfer drill as part of the Tailor Made D275 family.
In tests on an automotive wheel hub machined from P1 low alloy steel (190 HB), performed using a vertical machining centre with emulsion coolant, the new tool was used to produce 12.6 mm diameter holes with a 45° chamfer through a 14 mm thick workpiece. Up against a comparable competitor product, the CoroDrill 870 chamfer drill achieved 100% greater tool life, delivering a total drilled length of 60 m before tolerance limits were exceeded, compared with just 30 m using the competitor tool.
The CoroDrill 870 chamfer drill has one or two chamfer inserts depending on requirements. The use of two chamfer inserts produces thinner chips, and as a result is recommended for medium or high feed applications, in unstable conditions or where a large chamfer width is needed. Conversely, a single chamfer insert delivers a thicker chip and thereby gives better chip breakage in stable, low feed or small chamfer width applications. A range of insert sizes is available.
Sandvik Coromant recommends that the same feed rate be used when the chamfer insert is cutting. This is important, especially when drilling a blind hole, because a reduction in feed can result in undesirable long chips from the drilling operation.
