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For drilling of round bores twist drills with a roof-shaped point or with a centre point are applied. The spiral shaped cutting notches cause a fast throwing out of the shavings. The centre point supports the guideway of the driller.
An especially good guideway with simultaneously clean bore edges without torn out particles is reached by a twist drill with a staggered centre point where the external edges of the main cutting edges are in the cut first and thus support the guideway of the driller.
Figure 4 - Twist driller
1 with roof shaped point, 2 with staggered centre point
For cutting of long holes long-hole cutters (also called longitudinal drillers) with straight lengthwise cutting edges, one or two cutting notches and front cutting edges are applied. The straight lengthwise cutting edges cause the main cutting off. Because straight cutting notches are throwing out shaving worse than the spiral shaped ones deep cuttings are to be carried out with a long-hole cutter always in several steps.
Figure 5 - Long-hole cutter
1 with one cutting notch, 2 with two cutting notches
Clean the tools carefully from resin, varnish and glue after application!For cleaning use solvents only, no metallic auxiliaries are to be applied!
Keep the tool in containers to protect the cutting edges against any kind of damage!
Which tool is mainly applied for drilling of round
bores?
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What is the purpose of the centre point of the
driller?
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Which tool is applied for drilling and cutting of long
holes?
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