Single Point Lathe Tool

In a single point cutting tool, there will be a point contact between the cutting tool and the workpiece. Obviously the cutting tool should be provided with the clearances on the top. Underside and the side face. The cutting portion of the tool is formed by a face, cutting edge, flank, nose and base. 

The face is the top of the tool and is the surface over which the chip glides over it and passes away from the workpiece. 

The cutting edge is the part of the tool that does the actual cutting of the metal. 

The flank is the tapered surface directed below the cutting edge. 

The nose is the tip of the tool bit formed by the side and the end edges. 

The base is the bottom surface of the tool.

The functions of the different cutting tool angles are as follows:

1. Relief or clearance angles are ground on both the end and side faces of a tool to prevent it from rubbing on the workpiece.

2. Slide relief is the angle ground directly below the cutting edge on the flank of the tool.

3. End relief is the angle grounded from the nose of the tool.

4. Relief angles are necessary to enable only the cutting edge to touch workpiece.

5. Rake angles are ground on a tool to provide a smooth flow of the chip over the tool bit so as to move it away from the workpiece.

6. Side rake angle is ground on the tool faces away from the cutting edge. Side rake influences the angle at which the chip leaves the workpiece. A lathe tool generally uses side and back rakes. A general purpose lathe tool has a 14 degree side rake.

7. Back rake is ground on the face of the tool. Back rake angle influences the angle at which the chip leaves the nose of the tool. Generally 8 to 10 degree back rake is provided. 

8. End and side cutting edge angles are ground on a tool so that it can be mounted in the correct position for various machining operations.

9. End cutting edge angle usually 20 to 30 degree allows the cutting tool to machine close to the workpiece during turning operations.

10. Side cutting edge angle, approximately 15 degree, allows the flank of the tool to approach the workpiece first, thus reducing the initial shock of the cut to the tip point. This angle spreads the material over a greater distance on the cutting edge, thereby thinning out the chip.

11. Nose radius is the rounded tip on the point of the tool. The nose radius has tow functions to prevent the sharp fragile tip from breaking during use, and to provide a smoother finish on the workpiece during machining operations. A nose radius of 0.8 mm works well with most of the operations.