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The quality of the holes and the performance depend on the sharpness of the cutting edges and on the state of the boring tools and boring appliances.
Knife, three-square or square files with fine cut are used for sharpening. Correct sharpening of the boring tools requires utmost care, a lot of experience and exact knowledge of the mode of action of the individual types of bore bits.
The brad point, draw-in thread, pre-cutters and cutting edges are sharpened.
The sharpening process involves the following operations:
- Brad points without draw-in thread are uniformly filed from all sides so as to remain in the centre of the axis of rotation of the bit.- Draw-in threads are carefully filed by means of a knife file while the bit is rotating. No steps must be produced.
- Pre-cutters are sharpened on the inside only and against the direction of rotation of the bit.
- The cutting edge is sharpened so that the edge angles are not changed.
- All filed areas are stoned with an oil stone until no filing marks are left. This considerably increases the life of the boring tools.
What tools are used for sharpening of boring tools?
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Why must pre-cutters not be sharpened on the outside?
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On completion of boring, resin and dirt deposits are to be removed by means of hot water, petroleum or thinner. A thin film of acid-free grease will protect the boring tools against corrosion.
The bore bits are to be stored so as not to touch each other.
Three possible ways of storing are:
- The bits are stored in lying position in a box with several compartments.
Figure 6 Box with compartments for
storing bits
- The bits are suspended on a wooden suspension stand by means of the square tangs.
Figure 7 Bit suspension device
- The bits are stored in a wooden block with holes with the bits standing in upright position and their points pointing upwards.
Figure 8 Bit stand
Why must the bits not touch each other during storage?
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