Deep holes in stainless steel

CrazyDrill Cool SST-Inox is a solid carbide drill, in the diameter range from 1 to 6 mm, developed for the machining of stainless steels, heat resistant alloys (nickel based) and chrome-cobalt alloys. After the 2016 launch of the short versions of 6 x d and 10 x d, the program includes now drilling depths of 15 x d and 20 x d. Starting spring 2018 all standard sizes will be available from stock from all of their delivery centers.

Mikron Tool was able to build on the geometry of the short version of these drills and its “chip breaking profile” at the front of the tool which creates short and bent chips. Added to this they used an enlarged flute profile in the rear section of the flute which provided massive and constant cooling and chip evacuation. However, an additional measure was required for these drill lengths: The polishing of the flutes. The extremely smooth surface of the spiral flutes represents a significant difference when drilling more than 10 x d. Hence both features together assure even force requirements when drilling deep. Therefore, a single feed stroke is sufficient to reach the full drilling depth and a dependable flushing of the chips from the flutes. And all this with high feed and speed rates.

Maximum cooling performance

An additional characteristic, necessary to machine stainless materials process safe and with high speeds, is an efficient cooling. CrazyDrill Cool SST-Inox has spiralized and in the drill integrated cooling ducts which deliver the coolant right to the drill tip. These ducts have a cross section in the form of a drop which differentiate them from the usual round cross section.

The distinct advantage of these ducts is that they deliver up to 4 times more coolant volume. To guarantee this cooling performance also in small drill diameters, the shank is equipped with an additional Power Chamber (a cavity in the shank). This high cooling performance avoids the overheating and subsequent chipping of cutting edges and build-up of material.

Short drilling cycle, long tool life

The newly designed drills are very reliable and tool life can be significantly extended, especially when machining heat resistant alloys. This means for the user that he can produce his often very valuable work-pieces with a high process reliability. An example: A manufacturer of steam valves made from stainless austenitic steel DIN 1.4301 (AISI 304) which are used in coffee machines performed with one CrazyDrill Cool SST-Inox Ø 2,75 mm a bore with a depth of 15 x d in one single feed stroke and this by achieving a tool life of over 100’000 parts. This is double what was reached before.

Tests have shown that depending on material up the three times better tool life can be reached. According to the factor time represents also a big potential for savings. First experiences show that a hole depth of 20 x d drilled in one shot with the recommended cutting parameters can take 10x less time than usual. Even our researchers were surprised that it is possible to operate with the same feeds and speeds independent whether the hole is 6 x d or 20 x d.

Guaranteeing Quality with a clear Drilling process

In order to obtain good drilling quality with these drills, it is recommended to adhere to the manufacturer guidelines. All indicated cutting data are tested in manufacturing environments. Hence for a depth of more than 6 x d a pilot drilling is necessary with CrazyDrill Coolpilot which was developed as a compliment to the CrazyDrill Cool SST-Inox. This tool has been harmonized with the deep hole drill in its dimensions and tolerances. Also, speeds and feeds should be chosen within the recommended range. With this a maximum quality of the hole is assured in regards to cylindricity, axis runout and surface quality.

Soon available

The production works presently at full capacity, enabling to create a sufficient inventory to fill orders promptly. This requires some time. Starting spring 2018 all standard sizes will be available from stock from all of their delivery centers.