Simple internal and external broaching tools are schematically described in DIN 1415. The tooth section mostly comprises rough, finish and spare section being particularly different in rise per tooth. The cutting edge geometry has an important influence on the broaching result.
Broaching tool life
Tool life is also depending on a lot of influencing factors. When using component materials suitable for cutting, high quality machines and fixtures, proper designed broaching tools, and suitable coolant, the tool life between re-sharpening corresponds to 80 up to 250 meters and more. The definition of tool life end is based on experience, considering low tool and re-sharpening cost as well as the compliance with surface and dimension accuracy. Tool wear is depending on the following factors:
Component: material, structure, hardness, surface condition
Tool: cutting material, hardness, toughness, cutting edge geometry, grinding quality, number of broached parts
Machine: cutting speed, coolant, vibrations
Cutting speeds for broaching are generally below 30 m/min. In this range the cutting temperatures arrive at 200°C up to 600°C. Therefore, high speed steels (HSS) are mainly used for broaching tools. Using coated HSS or carbide as cutting material the capacity of broaching can be improved. Cutting speeds up to 120 m/min have been already realised. However, high cutting speeds require high drive power to accelerate and slowing broaching tools and broaching ram, so that equipment cost is increasing above average.
Mineral oils as coolant are used for lubrication and cooling in the contact zone area as well as for chip removal. Further development in the coating technology combining hard material coatings and lubricant soft material coatings may reduce the use of coolant and, in case of suitable component material quality, provide dry broaching without the use of any coolant.