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ISO 8434-1 Across‑flats dimensions

Date:Jun 15, 2019

For sizes up to and including 24 mm, tolerances for across-flats dimensions for forgings shall be−0 8 to 0,mm, and for sizes larger than 24 mm, they shall be −1

to 0 mm.


Hex tolerances across flats shall be in accordance with ISO 4759-1, product grade C. Minimum across-corner hex dimensions are 1,092 times the width across flats. The minimum side flat is 0,43 times the nominal width across flats.

Unless otherwise specified or shown, hex corners shall be chamfered 10° to 15° to a diameter equal to the width across flats, with a tolerance of −0 4 to 0,mm.


The dimensions across flats for nuts and on the bodies of the connectors.



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