How to Measure Nuts
A nut is identified by thread first, then geometry,

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QUICK RULE
A nut is identified by thread first, then geometry,
grade and finish.
THREAD
THICKNESS
SIDE VIEW
ACROSS FLATS (wrench size)
THREAD SIZE: use a known bolt/thread checker or internal-thread gauge.
WIDTH ACROSS FLATS: determines wrench/socket size.
THICKNESS/HEIGHT: distinguishes jam, regular, heavy and specialty nut forms.
FLANGE: measure flange diameter where applicable.
GRADE MARKING: identify separately from dimensions; a nut that threads on is not
automatically strong enough.
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-17B1A4 · thefastenerapp.com/fastener-guide/measure-and-identify/how-to-measure-nuts · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.

























