Thread Gauges

A thread gauge is a tool for identifying the pitch and diameter of screws, bolts, or threaded holes; use it by matching the workpiece threads to the gauge teeth or markings until you find the closest fit for both pitch (threads per inch or mm) and major diameter

Use a screw pitch gauge to identify thread pitch and approximate size for selection or repair; choose thread ring (external) or plug (internal) gauges when you need a go/no-go verification of dimensional conformance to a specific nominal size and tolerance

Look for sets that cover the standards you work with—common options include Unified UNC/UNF (imperial), Metric ISO (mm pitches), and occasionally Whitworth or specialized ACME threads; size ranges typically cover small fasteners up through several inches or tens of millimeters

Most consumer and shop-grade gauges are accurate enough for identification and routine verification; durability depends on material—hardened steel offers longer life and resistance to wear than stamped or plated alloys, which may deform with heavy use

Budget sets often cost under $50 and are fine for occasional use and hobby projects, but they may have fewer sizes, lighter construction, or less precise grinding compared with higher-end hardened or calibrated gauges

Keep gauges clean and dry, wipe off oil and debris after use, store them in their original case or a protective rack, and avoid dropping or using them as pry tools; periodically check critical gauges against a calibrated standard if precise tolerances are required

Digital and optical thread measuring tools can provide faster, repeatable numeric readouts and easier documentation for production environments, but they are generally more expensive and may require calibration and power, while traditional gauges remain simple, robust, and inexpensive