Correct bolt measurement prevents ordering mistakes and fitment issues. Start by identifying the diameter, overall length and thread pitch of the fastener. For countersunk screws, measure the full length including the head; for hex bolts and cap screws, measure from under the head to the tip.
Use a vernier caliper or micrometer to confirm the shank diameter. Metric fasteners are measured in millimetres, while imperial fasteners may use fractions or thread series such as UNC and UNF. Thread pitch gauges help confirm the distance between threads, such as 1.0 mm, 1.25 mm or 1.5 mm.
When checking an existing sample, also verify the head type, drive type, grade and finish. A bolt that matches in diameter but has a different pitch or thread standard will not assemble correctly.
Before purchasing, note the full specification in the format Diameter × Length, followed by material or grade and the standard, for example M8 × 40 SS 304 DIN 933.
Fastener Guides
How to Measure Bolt Size and Thread Pitch
A practical guide to measuring diameter, length and thread pitch correctly before ordering industrial fasteners.
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