How to Measure a Hex Bolt or Hex Cap Screw
Hex-head bolt and cap-screw length is normally the distance from the bearing surface under the head to the
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Hex-head bolt and cap-screw length is normally the
distance from the bearing surface under the head to the
end.
ACROSS FLATS
LENGTH
DIAMETER
LENGTH: underside/bearing surface of head -> end of fastener.
DIAMETER: nominal major diameter of the threaded shank.
THREAD: identify TPI for inch or pitch in mm for metric.
HEAD: measure width across flats for wrench/socket fit; do not use wrench size as the
nominal bolt diameter.
CALL OUT: diameter-thread x length, product/head style, grade/class, material/finish.
IDENTIFICATION ORDER
Product -> diameter -> thread -> length -> head/drive -> grade/material -> finish -> governing specification
REFERENCE ONLY. Verify the current ASME/SAE/ASTM/ISO/OEM standard and manufacturer data. Do not use as the sole basis for critical fastener selection or installation.
Fastener Guide reference FG-44F4A2 · thefastenerapp.com/fastener-guide/measure-and-identify/how-to-measure-a-hex-bolt-or-hex-cap-screw · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
