How to Measure Socket Head & Button Head Screws
Socket-head and button-head screws normally use the bearing surface under the head as the length datum.

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QUICK RULE
Socket-head and button-head screws normally use the
bearing surface under the head as the length datum.
SOCKET HEAD CAP
BUTTON HEAD
SOCKET HEAD LENGTH: underside of head -> end.
BUTTON HEAD LENGTH: underside/bearing surface -> end.
Measure nominal thread diameter and pitch/TPI.
Measure internal hex/drive size separately; drive size is not nominal screw size.
Flat-head socket screws are the exception: measure from top of countersunk head.
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-07899D · thefastenerapp.com/fastener-guide/measure-and-identify/how-to-measure-socket-head-and-button-head-screws · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.

























