Understanding Screw Pitch
Screw pitch is the distance between two matching thread points. It is usually measured crest to crest. The value may be given in millimeters or inches. Metric fasteners usually state pitch directly. Inch fasteners usually state thread density as TPI. This calculator supports both systems.
Why Pitch Matters
Pitch affects holding force, travel speed, adjustment control, and thread matching. A fine pitch gives slower movement per turn. It also gives better adjustment in many tools. A coarse pitch moves faster. It may be better for quick assembly. Wrong pitch can damage nuts, inserts, tapped holes, and machine parts.
Advanced Input Options
The calculator can work from thread count, TPI, lead, or travel. This helps when drawings are missing. You can measure several threads with calipers. Then divide the measured distance by the number of spaces or threads used. You can also rotate a screw and measure linear motion. This is useful for lead screws, vises, jacks, slides, and adjusters.
Lead and Multi-Start Threads
Pitch and lead are not always the same. On a single-start screw, lead equals pitch. On a two-start screw, lead is twice the pitch. On a three-start screw, lead is three times the pitch. Multi-start screws move more distance per turn. They are common where fast travel is needed with smooth engagement.
Practical Measurement Notes
Clean the thread before measuring. Avoid damaged crests. Measure across several threads to reduce error. Use the same unit for related diameter and length inputs. For small screws, a thread gauge gives quick confirmation. For machine screws, compare the result with standard tables before cutting, tapping, or ordering parts.