DEEP DRILLING STRATEGY Recommendation for a length starting from 12xD (Article 010 642 010 644 ) and obligatory for a length starting from 20xD (Article 010 646 010 64

DEEP DRILLING STRATEGY Recommendation for a length starting from 12xD (Article 010 642 010 644 ) and obligatory for a length starting from 20xD (Article 010 646 010 648 010 650 ) with at least 40 bar internal cooling for a save chip removal. 1. Pilot drilling The diameter of the pilot drill needs to be 0.02 mm bigger than the chosen deep hole drill. A two flute drilling tool with 140 top angle is recommended. The depth of the pilot hole should be 1.5 up to maximum 5xD. 2. Run into the pilot hole of the deep hole drill Running in without internal cooling A rotation speed of max. 500 rpm and 25-30%of the recommended feed rate will be programmed 1 to 2 mm before the ground of the pilot hole running-in is finished. Attention For start-up of the spindle and pressure generation of internal cooling enough holding time is absolutely necessary 1...2 mm 3. Deep hole drilling Use recommended cutting data The feed rates need to be reduced by 50% in case of cross boring or at the end of the hole. 4. Moving out of the deep hole drill After the maximum drilling depth was achieved the deep hole drill needs to be moved out of the drill hole by 1-2mm (depending on diameter) possibly with a programmed retention time at a too low coolant pressure. Then the rotational speed has to be reduced down to max. 500rpm or the spindle has to be stopped Moving out of the drill hole with a programmed feed rate (but not with fast motion) 44 NORGAU Cutting tools 1