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2015-10-27

Machining Stainless Steel - hints and tips

 

At Dormer Pramet we believe in sharing the knowledge gained during more than 100 years of working within the metal cutting industry.

​​​Here are a selection of useful hints and tips for machining stainless steel.

If you have a specific challenge or question not covered here, please speak to one of our technical sales engineers who will be happy to help.

Coolant & lubrication:

A generous flow of cutting fluid removes heat from the chip, helps chip breaking and at the same time, improves dimensional stability of the component.

Cutting tools with through coolant provide instant cooling at the cutting interface, which also helps chip breaking and evacuation.

When using flood coolant, always ensure a plentiful supply, as any period of coolant starvation can cause temperature fluctuations. This, in turn, can cause thermal cracking, resulting in reduced tool life.

Neat cutting oils work very well but, if using an emulsion, an eight to ten per cent concentration is recommended.

Feed rates:

Stainless steels can vary slightly between different suppliers and batches. Therefore, when choosing cutting data it's always a good idea to begin at the lower region of the manufacturer's recommendations.

High feed rates can cause heat transfer into the cutting tool, increasing tool wear.

Work hardening:

Some stainless steels are prone to work hardening during machining. This can have a negative effect on tool life and also reduce the life of subsequent tools used.

To minimize this, avoid using tools with worn edges which could accelerate tool wear and cause breakage. Make regular checks for signs of wear and change tools or inserts regularly.

Also, try to avoid any dwells or pauses in the cutting process as this will cause heat build-up and increase work hardening.

Mechanical properties:

The high strength of stainless steels combined with their high ductility makes chip breaking more difficult. This increases the risk of vibration, which can affect surface finish quality and reduce the service life of the tool or insert.

To address this, always make sure tooling and workpieces are stable and well clamped. Always keep tool overhang to a minimum, especially when drilling or internal turning.

To help reduce vibration, use sharp tools or inserts with a small nose or corner radius.

Threading:

When tapping stainless steels, tool life can be increased by pre-drilling the hole 0.1 mm larger than recommended.

This will reduce torque levels encountered during threading which, in turn, increases tool life and performance.


 
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