How to Design Threads for Manufacturing

Core Principle

Thread manufacturability depends on its type (internal/external), depth, and location. Designs should prioritize standard threads that can be created with taps and dies.

Internal Threads (Tapped Holes)

• Maximum effective thread depth: 3 times hole diameter (3xD)
• Blind holes: Leave 3-5 pitches clearance at bottom
• Allows space for incomplete threads and chip evacuation

External Threads

• Design thread relief (undercut) at thread end
• Allow for several incomplete threads
• Full thread to shoulder is difficult and expensive

Best Practices:
• Use standard coarse threads (UNC/M series) unless fine threads required
• Coarse threads are stronger, less prone to cross-threading, and faster to machine