CHESTER Craftsman, Инструкция по эксплуатации

Страница: 15 / 53

Plan Profile of Tool
The plan shape of the tool is often dictated by the shape of the work, but it also has an effect on the tool
life and the cutting process. Figure 6 shows two tools, one where a square edge is desired and the other
where the steps in the work end with a chamfer or angle. The diagram shows that, for the same depth of
cut, the angled tool has a much greater length of cutting edge in contact with the work and thus the load
per unit length of the edge is reduced. The angle at which the edge approaches the work should in theory
be as large as possible, but if too large, chatter may occur. This angle, known as the Plan Approach
Angle, should therefore be as large as possible without causing chatter.
Figure 6. Plan Approach Angle
The trailing edge of the tool is ground backwards to give clearance and prevent rubbing and a good
general guide is to grind the trailing edge at 90° to the cutting edge. Thus the Trail Angle or Relief Angle
will depend upon the approach angle.
A small nose radius on the tool improves the cutting and reduces tool wear. If a sharp point is used it
gives poor finish and wears rapidly.
Chester UK Craftsman Lathe
14