Cutting processes involve using hard materials to cut soft materials, and pressure-resistant materials to cut brittle materials. Metal materials, depending on their grade, are classified as hard or soft, and as tough or brittle. Metal cutting tools are made of very hard steel.
High-Speed Cutting Tools and Low-Speed Cutting Tools
Metal cutting tools are broadly classified into high-speed cutting tools and low-speed cutting tools. Generally, low-speed cutting tools are used manually, while high-speed cutting tools are used on machine tools. Low-speed cutting tools include carbon tool steel and alloy tool steel, while high-speed cutting tools include high-speed steel, ceramic tools, and cemented carbide. Low-speed cutting tools typically include: files, chisels, hand saw blades, taps, dies, broaches, etc. High-speed cutting tools typically include: twist drills, various turning tools, milling cutters, boring tools, planing tools, broaches, machine taps, etc.
Hot Hardness of Cutting Tools
A significant difference in performance between high-speed and low-speed cutting tools lies in their hot hardness. Low-speed cutting tools have poor hot hardness, generally below 200℃; high-speed cutting tools have excellent hot hardness, generally above 600℃. Hot hardness refers to the property of maintaining high hardness at high temperatures. Friction generates heat, and frictional heat is generated during high-speed cutting of workpieces. The higher the relative speed, the higher the frictional heat generated. High-speed cutting tools still have high hardness under the high temperature generated by intense friction and can continue machining. High-speed machine tools use high-speed cutting tools, while low-speed cutting tools lose their hardness at high temperatures and can only perform cutting work in lower temperature environments.
Differences in the Use of High-Speed Steel and Carbide
Both high-speed steel tools and carbide tools are high-speed cutting tools, but there are significant differences in their use:
High-speed steel: Hard and tough, maintaining high hardness below 600℃.
Carbide: Hard and brittle, pressure-resistant and wear-resistant, maintaining high hardness below 1000℃.
In practical use, the following points should be noted:
1) High-speed steel tools, due to their good toughness, can be used for cutting at very low speeds, while carbide tools must be used at high speeds; the cutting speed cannot be low, otherwise the cutting edge will chip.
2) During cutting, the cutting fluid for high-speed steel tools can be added continuously or intermittently; however, the cooling for carbide tools must be continuous, added from start to finish, and not added halfway through, otherwise the tool will crack due to sudden heating and cooling.
3) Because carbide tools are pressure-resistant and wear-resistant, they are suitable for cutting hard and brittle cast iron workpieces in actual cutting.
4) When sharpening tools, high-speed steel tools can be continuously ground on a grinding wheel; however, carbide tools cannot be continuously ground on a grinding wheel, otherwise chipping will occur.
Rake Angle and Wedge Angle
The rake angle of a tool is variable, depending on the material of the workpiece. The rake angle controls the sharpness of the tool, while the wedge angle controls the strength of the tool. For any mechanical cutting process, the various angles that the cutting tool is ground are all aimed at minimizing cutting forces and maximizing tool life.
Post time: Nov-27-2025