Thread is torn or galled

?Likely causes

• Welding to the tapOne maker^[1][2][3]
• Insufficient sharpness, or rake angle unsuited to the workpiece materialOne maker^[3][2][1]
• Poor chip evacuation or cloggingAgreed by 2+ makers^[1][2][3][4]
• Poor feed (lead) or axis runoutOne maker^[1]
• Tap drill hole is work hardened, tilted, or too smallOne maker^[1][2]
• Variation in workpiece material, hardness, or structureOne maker^[1]

✓Fixes

Cutting conditions

• In a synchronized feed setup, evacuate chips with step machiningOne maker^[3]
• Reduce the cutting speedOne maker^[1][2]

Tool

• Use a sharp tap suited to the workpiece material (e.g. for aluminum)One maker^[3][1][2]
• Use a surface-treated tap such as TiNOne maker^[1][2]
• For horizontal machining, use a low-helix spiral tap to prevent chips from wrapping around itOne maker^[4]

Setup

• Make the tap drill hole larger, and prevent tilt and work hardening of the holeOne maker^[1][2]

Coolant

• Increase the cutting fluid concentration and supply enough (also review the type, replacement timing, and contamination by other oils)One maker^[3][1][2]

▦Notes by material

• Aluminum castings (AC4CT6, etc.): Tearing is caused by one of insufficient sharpness, poor chip evacuation, or insufficient lubrication. Choose the countermeasure according to the cause^[3]

↔Related problems