Advanced Turning

High-speed steel turning tools are usually a solid type tool and the cutting edge is ground on the tool itself. Compared to other turning tools made of different materials, high-speed steel turning tools have a very high toughness and are suitable for unstable machining such as low speed and interrupted machining. Low speed machining however can create a built-up edge that can lead to micro-chipping occurring on the cutting edge when the built-up edge is removed. Therefore, for low speed machining (under approximately 50m/min. for steel), an extremely tough high-speed steel tool is more effective.

 

High-speed steel tools are convenient to handle due to the ease of the initial grinding and re-grinding and because of the overall low costs involved.

Brazed carbide tool holders have a steel shank on which the cutting edge is brazed. The cutting edge is then ground according to the application. The tool holder shape is designated by JIS according to the machined part and its use.

 

For the cutting edge itself, high-speed steel or a P, M or K group cemented carbide is used dependant on the cutting speed.

 

Tool grade and cutting edge geometry are decided according to the workpiece material and geometry of the workpiece. The cutting edge is ground to form a rake angle, a clearance angle and chip breaker. Grinding of each tool requires time and a skilled operation, therefore more than 90% of tool holders currently used are an indexable insert type.

Indexable insert type tool holders have, as the name explains, cutting edges that can be replaced. The cutting edge in this case is called an insert. There are high-speed steel and cemented carbide insert grades available but cemented carbide inserts are much more widely used.

 

The main feature of indexable holders is that it’s possible to use various inserts with different properties on a single shank and to use it according to the application required. In addition, regrinding is unnecessary because the worn cutting edge can be simply replaced.

 

Considering the short preparation time needed prior to machining, regular and accurate cutting edge geometry and a reduction in the numbers of tool holders used, indexable insert type holders have overwhelming cost advantages.