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Technology 1-5
Cutting edge and selecting cutting edge geometry
By cutting edge, we understand a geometrically spec- ified edge of a cutting tool that is used for machining a material. The precise shape of the cutting edge of a cutting tool is called its “cutting edge geometry“. It is significantly responsible for the service life of a tool and determines the necessary sharpness. The manufacturing and maintenance (tool sharpening) of cutting edges is the responsibility of the diamond toolmaker.
Cutting edge geometry
Clearance angle
The clearance angle (symbol: α) on a tool cutting edge describes the angle of clearance between the tool and face being machined during chip removal. It is typical- ly important for such jobs as turning and milling and reduces friction between the two parts. The clearance angle is always selected to be just large enough for the tool to cut sufficiently freely, depending on the material. A small angle is selected in the case of hard, short-chip- ping materials, such as high-alloy steels. A large clear- ance angle, on the other hand, is chosen for soft, form- able materials such as plastics.
The clearance angle is formed by the cutting edge plane and flank and measured vertically to the main cutting edge. Together with the lip angle, it forms the cutting angle. The clearance angle, lip angle and chip angle al- ways add up to 90°.
Lip angle
he lip angle (Symbol: β) is the angle of the cutting edge of a tool when removing material by means of machin- ing. Together with the clearance angle, it forms the cut- ting angle. The clearance angle, lip angle and chip angle always add up to 90°.
Theoretically, the smallest possible lip angle, that is the “sharpest possible“ tool, is optimal for chip removal, because the cutting forces are smallest here. However, the instability of the cutting edge which then occurs, low heat dissipation, as well as the unwanted build-up of chips when machining some materials means the lip angle selected always becomes a compromise between cutting ability and the stability of the cutting edge.
The cutting angle
The cutting angle of a tool cutting edge is the angle between the cutting face and workpiece during chip
removal. The cutting angle is made up of the clearance angle and lip angle. The cutting angle and chip angle always add up to 90°.
The chip angle
The chip angle (symbol: γ) of a cutting edge influences the compression and discharge of the chips, as well as heat dissipation during
chip removal. It is de-
fined by the datum plane
and cutting face.
Positive chip angles un-
der 90 degrees allowv
the chips to slide more
smoothly over the cut-
ting wedge. Most of the
heat is dissipated with
the chips. This makes ad-
hesion of the chips onto
the cutting wedge diffi-
cult. The disadvantage
of a positive chip angle
is the production of long
chips, which can howev-
er be broken by renewed
diversion through the
chip breaker. To increase
the stability of the cutting edge when removing chips from hard materials, a smaller or even negative chip an- gle can be selected. In the case of a negative chip angle, we talk about “abrading” and in the case of a positive chip angle “cutting”.
cutting face mini cutting edge
shank
feed direction main cutting edge
major flank corner
Angle in machining
tool
chip angle
lip angle
clearance angle
work piece
cutting angle
chip space
bevel grinding
chi
cutting edge step
p
angle
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© DiaTec – Diamant technology LLC Technical modifications reserved All dimensions in mm
V 2.0
clearance angle
lip angle