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Knowing the tools, their shapes, kinds and application is necessary for an economic working.
The kind of tool to be applied in each case is determined by the shape of the workpieces to be machined.
If much material has to be removed, start working with the straight tool. If the demands stipulated for the surface quality are high, use the finishing tool.
So for each job the corresponding tool must be used.
The slotting tools are similar to the turning tools and have various shapes.
The slotting tools are differentiated in general by their shank form, position of the primary cutting edge, cutting edge form and application.
Figure 8 - Classification of tools
according to shank form
(1) straight tool
(2) bent tool
(3) swan-necked tool
(4) offset tool
Figure 9 - Classification of tools
according to tool tip position
(1) left-hand tool
(2) right-hand tool
Figure 10 - Classification of tools
according to tool tip shape
(1) broad-nose tool
(2) pointed tool
Figure 11 - Classification of tools
according to the application
(1) shoulder tool
(2) parting-off tool
(3) grooving tool
(4) hook tool
(5) forming tool
How to distinguish between left-hand and right-hand
tools?
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The slotting tools are standardized with regard to their shape and dimension. Generally applicable international agreements exist also as far as the specification of the angles and faces and the designation of the various kinds of tools are concerned
Tool angles
Only when the cutting edges are properly ground, economic working with the tools is possible. This requires to know the different angles at the tool tip.
The shape of the cutting edge of the tool is determined by the following angles:
a = angle of clearance
b = wedge angle
g = rake angle
d = cutting angle (a + b)
Figure 12 - Tool angles
1 - angle of clearance a
2 - wedge angle b
3 - rake angle g
- The wedge angle lies between tool flank and tool face. Its size is determined by the strength of the material to be machined. Hard material requires a large wedge angle, e.g. steel b = 60° - 75°. Soft material requires a small wedge angle, e.g. aluminium: b = 40°.
- The angle of clearance is determined by the tool flank and the horizontal line to the workpiece. On principle, the angle of clearance is chosen to be only as large as necessary so that the tool does not excessively rub against the workpiece and does not get stuck during the return stroke (recommended value 4° - 6°).
- The rake angle is formed between the tool face and the vertical line set up in the contact point on the tangent. In general, the rake angle should be kept large to allow an easy cutting of chips. However, the size of the rake angle is limited by the size of the wedge angle which depends on the material.
- The cutting angle is formed by the angle of clearance and the wedge angle together (a+ b = g).
Special features of the tools
Shank and tool point can be of the same material and form a unity (solid steel).
The shank is often made of mild steel in order to save valuable cutting-tool material (high-speed steel) or because the properties of other cutting-tool materials (hard metals, ceramic cutting-tool materials, diamonds) require this.
The cutting part can either be butt welded, soldered or welded on as tool tip or clamped firmly in place.
Explain the terms "tool face" and "tool
flank"!
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