Drill America Cobalt Aircraft Extension Drills Are Similar To High-Speed Steel, But With More Cobalt For Improved Performance When Cutting Harder Metals Such As Stainless Steel Or Nickel Alloys Gold Oxide Is A Thinner Oxide Surface Treatment Than Black Oxide Typically Used To Identify Cobalt Steel Tools Performance Is Similar To Uncoated Tools Drill America Aircraft Extension Drills Are Manufactured To National Aerospace Standard 907 The 135A Split Point Is Self-Centering And Reduces Thrust Sizes Smaller Than 116 In Have The 118A Standard Point Drill America Aircraft Extension Drills Are Available In 6 In And 12 In Overall Lengths When Extra Reach Is Required