How to Select the Right TNMG Insert Grade for Steel, Stainless Steel, and Cast Iron

when it comes to machining metal, selecting the right tnmg (triangular negative multi-edge) insert grade is crucial for achieving optimal performance and tool life. the right insert will depend on the material you are cutting, whether steel, stainless steel, or cast iron. here’s a guide to help you choose the appropriate tnmg insert grade for each material type.

1. selecting inserts for steel

for machining carbon steel and alloy steel, look for tnmg insert grades designed specifically for these materials. generally, a carbide grade with a black or grey coating is preferred, as this improves wear resistance and helps maintain edge integrity during machining operations. grade classifications such as p15 or p20 are suitable for general-purpose steel machining.

high-speed cutting and heavy machining tasks may benefit from coated carbide inserts, which can withstand elevated temperatures and extended wear. additionally, consider using a positive relief insert to reduce cutting forces and improve chip flow.

2. choosing inserts for stainless steel

stainless steel is known for its toughness and work-hardening characteristics, which can pose challenges during machining. for stainless steel, choose tnmg inserts with a fine grain structure and a high-temperature resistant coating, typically labeled with a grade like m10 or m15. these inserts are designed to handle the unique cutting forces associated with stainless steel without chipping or breaking.

furthermore, a chip breaker design can be beneficial for stainless steel. this helps control chip flow and prevents binding, allowing for smoother operations and greater tool life. always opt for a lower cutting speed and higher feed rate to minimize heat generation and improve machinability.

3. opting for inserts for cast iron

machining cast iron requires a different approach due to its brittle nature and abrasive characteristics. for this material, select tnmg inserts that are classified as grade k, such as k10 or k20, which are designed for cast iron applications. inserts made from high-carbide content with a tough substrate will excel in wear resistance and chip removal efficiency.

it is advisable to use a stronger insert with tougher cutting edges to handle the impact of cast iron machining while preventing chipping and breakage. sharp edges are preferred, as they help in reducing cutting forces and improving surface finish. a negative rake design can also be beneficial in effectively managing chip control in cast iron machining operations.

conclusion

choosing the correct tnmg insert grade is essential in maximizing efficiency and extending tool life. assess the material characteristics and match them to the appropriate insert grade: p grades for steel, m grades for stainless steel, and k grades for cast iron. keep in mind that each application may also require adjustments to tooling geometries to achieve optimal results. make informed choices based on your specific machining requirements to ensure the best possible outcomes.