EMO 2019 / Mikron Tool Drilling in one stroke

Editor: Steffen Donath

Small, deep and fast, these are the characteristics of the Crazy Drill Cool SST-Inox. With a special cooling design, the drill aims to take on tough challenges.

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Short chips are a significant factor to drill in one single stroke.
Short chips are a significant factor to drill in one single stroke.
(Source: Mikron Tool)

Small, deep and fast, these are the characteristics of the small drill Crazy Drill Cool SST-Inox. Due to internal coolant ducts, improved geometry and special coating, the machining of stainless steels, nickel based super alloys and Crco-alloys has become simpler and process stable, according to Mikron Tool. This goes also for small diameters as well as deep bores.

The range includes through coolant drills in six different working lengths: up to 6 x d, to 10 x d, to 15 x d, to 20 x d, to 30 x d and to 40 x d. In addition, there is a short i.e. pilot drill for a max bore depth of 3 x d. Up to a bore depth of 20 x d these tools are available from dia. 0.039” (1 mm), the longest one from .078” (2 mm). The entire range goes to a max diameter of .236” (6 mm).

Because drills with spiralised coolant ducts are available already; also in the small diameter ranges. However, many get into trouble with tough-elastic materials or with the poor heat conductivity of super alloys. Here the cooling through “classic” round ducts is even with high pressure insufficient. A premature edge chipping, packing of chips, buildup of the flutes prevents a process stable drilling. Exactly this is important for industries which produce from valuable material even more valuable finished parts. Markus Schnyder, head of Mikron Tool International and one of the initiators of the new tool, knows all about the problematic: “For many years our customers reached the limit when drilling stainless steel. The process was not stable and too slow; thus, machining became extremely expensive.”

The coolant ducts have the largest possible diameter and are drop shaped. These ducts are located in an area with little stress and therefore the stability of the tools is not jeopardised. Comparing to the conventional round diameter, these ducts afford a 4-time higher coolant flow. At diameters under .118” (3 mm) a power chamber in the shaft reduces the length of the ducts and provides higher coolant pressure.

The advantage of the efficient supply of coolant to the drill tip, increases tool life because an overheating of the cutting edges is avoided right from the beginning. Combined with the innovative tip geometry, the cooling helps greatly to break and flush out the chips from the flutes. All these characteristics make it possible to work with higher cutting parameters (speed and feed) and to drill in one single stroke.