Over the years, many of our customers have come to us because they were regularly breaking taps. One case involved a shop owner who was machining a critical part for a radar component.
Made of TiAl 64V titanium, the part required 683 blind holes. Because of the tapping operation, his customer had to allow a tap deviance of .040″ in depth to allow for the thread clearance. This meant that the holes had to go from a depth of .150″ to .190″.The 2-56UN thread’s major diameter was .086″, and the drill diameter .070″. Repeatability was nearly impossible on his CNC equipment, and he literally came in every Saturday to tap the holes by hand. When he started talking with us, he was breaking his taps after only 20 holes — an extraordinarily short tool life.
By re-examining his technology, and switching to thread milling, he was able to accomplish the threading of 683 holes with a single thread-mill on his CNC equipment. Despite the number of passes, the wear factor between the first and the last holes could only be measured in tenths, and the customer was able to get the thread detail back to its original .150″ full thread depth. Perhaps just as important, his Saturdays are now “tap-free.”