Thread Pitch Identifier

Understanding Thread Pitch

What is Thread Pitch?

Thread pitch is the distance between threads on a screw or bolt, measured from the crest of one thread to the crest of the next. It's a critical specification for ensuring proper fit between bolts, nuts, and threaded holes.

Metric vs Imperial Thread Pitch

Metric threads measure pitch in millimeters (the distance between threads). For example, M8 × 1.25 means an 8mm diameter bolt with 1.25mm between each thread.

Imperial threads measure in TPI (Threads Per Inch) - the number of threads in one inch of length. For example, 1/4"-20 means a 1/4 inch diameter bolt with 20 threads per inch.

Coarse vs Fine Threads

• Coarse threads (UNC/Metric Coarse): Fewer threads per inch, faster assembly, better for softer materials, less prone to cross-threading
• Fine threads (UNF/Metric Fine): More threads per inch, greater strength, better vibration resistance, used in precision applications

Common Applications

Automotive: Most automotive applications use coarse threads for ease of assembly and resistance to dirt and corrosion.

Machinery: Fine threads are common in precision machinery where adjustability and holding power are critical.

Construction: Coarse threads dominate in construction for quick assembly and better grip in softer materials like wood.

How to Measure Thread Pitch

Use a thread pitch gauge - a tool with multiple blades, each marked with different pitches. Match the blade teeth to your thread until you find a perfect fit. For metric threads, the gauge shows pitch in mm. For imperial threads, it shows TPI.

Why Thread Pitch Matters

Using the wrong thread pitch can result in:

• Stripped threads and damaged parts
• Loose connections and potential failure
• Cross-threading and misalignment
• Reduced strength and load capacity

Always verify thread pitch when replacing fasteners, especially when working with imported parts that may use different standards.