Crazy But Cool - A New Small Hole Drilling Process From Mikron Tool

Holes between 1 mm and 4 mm diameter can now be drilled up to 15 times the length to diameter ratio to very high accuracy with penetration rates of up to 20 times faster than normal applied feeds following a breakthrough in small solid carbide drill technology and development of the cutting process by Mikron Tool of Agno, Switzerland.

The CrazyDrill Cool, aptly named due to its almost unbelievable performance as a twist drill, combines the latest generation carbide, Mikron developed cutting edge technology, special coatings and a progressive helix grooving. As a result, penetration of the workpiece is improved with through the tool coolant fed directly to the cutting zone which maximises chip removal and extends cutting tool life in a wide range of materials from non-ferrous to heat treated steel.

These high performance drills are available from stock between 1 mm and 4 mm diameter in increments of 0.05 mm and lengths of 6XD, 10XD and 15XD. For tools up to 2.5 mm diameter, Mikron has been able to improve coolant flow to the cutting zone by up to 300 per cent, even when applied at low pressure, by incorporating a ‘power chamber' set into the tool shank. As a result, this copious supply of cutting fluid through the tool is ideal to cool and lubricate the tool and is especially successful when difficult to machine materials have to be processed.

The Mikron developed process, uses two stages of drilling that enables maximum productivity to be obtained. Initially, a Mikron PilotDrill is used to position the hole centre and provide a ‘start bush' or guide hole in the material to a depth equal to twice the diameter of the tool. The same tool can also be used to chamfer or break the edge of the hole within cycle and also enables holes to be produced at an angle if required. As a result, it creates a very accurate start position for the main drill preventing initial wander, helps stop any deviation from the target area and prevents tool breakage as the drill starts to engage in the cut.

Important in the overall performance of CrazyDrill Cool is the considerable reduction in the cycle time. This is achieved due to its ability to drill up to 10 times the depth to diameter ratio in a single step before any peck stages have to be initiated in order to relieve the tool and break up the swarf.

In recent trials on 90 Mn CrV8 tool steel a 1.5 mm hole was produced some 22.5 mm deep. The PilotDrill initially created a start hole 3 mm deep that was followed by CrazyDrill Cool running at 10,600 revs/min and 0.10 mm/rev feed rate that enabled the material to be penetrated at 1,060 mm/min. During the cycle, which covered a drill depth of 22 mm, the tool only had to be peck fed and redrawn four times.

There are three variants of CrazyDrill Cool – a short version for holes up to six times diameter to length ratio, one of medium length for holes up to 10:1 and a long series drill which enables holes up to 15:1 to be drilled. Both coated and uncoated tools can be supplied according to materials to be machined and a regrinding service is available from Mikron for tools over 1.5 mm diameter. Special customised tool dimensions can also be supplied under Mikron's ‘Star Service' together with certification of conformance.

Source: Mikron Tool SA Agno