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Coolants in CNC (Computer Numerical Control) machining centers often perform under demanding conditions involving high speeds, hard metals and close tolerances. Without their special abilities to provide lubricity, maintain viscosity, and transfer heat, CNC machining might not be where it is today.

Huffman Corporation (Clover, South Carolina) is a manufacturer of multiaxis CNC grinders. These machines are designed and built primarily for cutting tool manufacturing rather than the regrind market.

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Huffman machines are serving as workhorses in the aerospace, cutting tool, and medical device industries. These CNC grinders work to produce turbine engine parts including blades and vanes and other components for both land and aero turbines. For the cutting tool industry they cover the gamut from end mills, inserts, spade drills and other tools where a fine surface finish is required. The machines are also used to manufacture medical devices such as joint replacement parts and implants, and for reamers and drills used in these operations.

"While we will work with whatever the customer specifies in a coolant, we will typically use and recommend Henkel Surface Technologies' (Madison Heights, Michigan) Circlene FG 20 coolant," says Daniel T. Gerstner, Huffman's manager, new process development.

"Over the years, we have tested many coolants and based on those tests we determined that Circlene performed the best," says Thad Baird, Huffman's vice president, operations. "As a result we have been using the coolant since the late '70s. When we submit quotations to our customers, we also include a recommendation for the Circlene products."

"(Circlene is) an extremely heavy duty grinding oil that possesses the capability for grinding some of the hardest metals and thread application," says Mr. Gerstner. "The chemical ingredients of this coolant, because of its polar nature, allow the grinding wheel to hold its form for better wheel life."

"If the customer doesn't specify a coolant, we match up similar speed rates and materials and then make our recommendations based on that data. We always prefer using the coolant that is used during the development stage, and that has been Circlene," he adds.

"We study the workpiece material, considering lubricity, and the heat removal required. If the coolant lubricity is right we know it will allow the machine to grind with less heat being generated," says Mr. Baird.

Both Circlene FG 20 and FG 20 AMO (antimist oil) enhance grinding wheel performance for closer tolerances and elimination of grinding checks. They are medium viscosity oils, light colored and compounded for stock removal with a minimum wheel dressing. Typical properties for these coolants are:

• Viscosity @ 100 F 200SUS
• Flash point F 410 F min.
• Pour point F +5
• Color Amber
• Pounds per gallon 7.5

The Circlene line of products is also available in a variety of viscosity grades to satisfy different process needs.

"Stan Huffman, founder of our company, originally came up with the idea to grind ball nose end mills, and we took off from there. The company holds patents for developing an eight axis tool cutter with CNC control, and we shipped our first machine in 1977," Mr. Baird explains. "At present, we produce 40 to 45 machines annually. A standard grinder can be shipped from order receipt to customer acceptance in approximately 14 to 16 weeks. However, special machines can take up to one year to produce."

Huffman Corporation made a tried and tested coolant its product of choice, is recommending it to its customers, and has incorporated it into its own system for CNC grinding machine production.