T-Drill S-80, Инструкция по эксплуатации

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INSTRUCTION MANUAL
74
8.3.3. RESHARPENING OF THE DRILL BIT
¨NOTE!
¨
Resharpening of the drill bit demands a special professional skill
- a wrongly sharpened drill bit reduces the quality of the collar.
The parts of the bit: α = Clearance angle, ɣ = Chisel edge angle, 1. Cutting edge, 2. Body
clearance surface (land), 3. Rake face, 4. Flute.
The patented cutting geometry of the T-DRILL bit is designed in such a way that a perfect
pilot hole without burrs can be achieved at a low feed rate. However, this presupposes
that the cutting edge is always kept sharp.
When do we have to resharpen?
When the cutting performance of the bit declines, it does not seem to penetrate the tube
surface easily or burrs occur on the edge of the pilot hole, it is time to resharpen. (Note!
Burrs may also be a sign of insufficient lubrication). Use of a dull bit must be avoided,
because a dull bit wears out very quickly and thus its life expectancy will be relatively
short.
Where do we resharpen?
The bit is resharpened at the rake face only. The body clearance surface is never to be
sharpened, because even the slightest variation in the anding angle will radically reduce
the cutting characteristics of the bit.
For the resharpening the following equipment is needed:
- A tool grinding machine equipped with a vertically tiltable rotary table
- A fine-grained, thin grinding wheel which fits in the flute
- A straight pin which fits in the cutting-groove by means of which it is easier to set the bit
in the correct position.
The correct positioning for grinding
1. Fasten the drill shank in the clamping fixture and put the straight pin into the flute. Set
the pin parallel with the slide bars of the grinding machine carriage both vertically and
horizontally. (See figure next).