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IFI-128 is a standard developed through the procedures of Industrial Fasteners Institute. IFI-128 was first published in 1978 and reaffirmed, without technical change, in 1986 and in 2000.
Hex Coupling Nuts
Unit of Measure
1 2 

Item #

Description

Nominal Size or Basic Major Dia. of Thread

Basic (F)

Max. (G)

Basic (H)

HCN02500XXX N/A Hex Coupling Nut, 0.2500" Nominal Dia. N/A 1/4 in N/A 3/8 in N/A 0.433 in N/A 3/4 in
HCN03125XXX N/A Hex Coupling Nut, 0.3125" Nominal Dia. N/A 5/16 in N/A 1/2 in N/A 0.577 in N/A 15/16 in
HCN03750XXX N/A Hex Coupling Nut, 0.3750" Nominal Dia. N/A 3/8 in N/A 9/16 in N/A 0.650 in N/A 1-1/8 in
HCN04375XXX N/A Hex Coupling Nut, 0.4375" Nominal Dia. N/A 7/16 in N/A 11/16 in N/A 0.794 in N/A 1-5/16 in
HCN05000XXX N/A Hex Coupling Nut, 0.5000" Nominal Dia. N/A 1/2 in N/A 3/4 in N/A 0.866 in N/A 1-1/2 in
HCN05625XXX N/A Hex Coupling Nut, 0.5625" Nominal Dia. N/A 9/16 in N/A 7/8 in N/A 1.010 in N/A 1-11/16 in
HCN06250XXX N/A Hex Coupling Nut, 0.6250" Nominal Dia. N/A 5/8 in N/A 15/16 in N/A 1.083 in N/A 1-7/8 in
HCN07500XXX N/A Hex Coupling Nut, 0.7500" Nominal Dia. N/A 3/4 in N/A 1-1/8 in N/A 1.299 in N/A 2-1/4 in
HCN08750XXX N/A Hex Coupling Nut, 0.8750" Nominal Dia. N/A 7/8 in N/A 1-5/16 in N/A 1.516 in N/A 2-5/8 in
HCN10000XXX N/A Hex Coupling Nut, 1.0000" Nominal Dia. N/A 1 in N/A 1-1/2 in N/A 1.732 in N/A 3 in
HCN11250XXX N/A Hex Coupling Nut, 1.1250" Nominal Dia. N/A 1-1/8 in N/A 1-11/16 in N/A 1.949 in N/A 3-3/8 in
HCN12500XXX N/A Hex Coupling Nut, 1.2500" Nominal Dia. N/A 1-1/4 in N/A 1-7/8 in N/A 2.165 in N/A 3-3/4 in
HCN13750XXX N/A Hex Coupling Nut, 1.3750" Nominal Dia. N/A 1-3/8 in N/A 2-1/16 in N/A 2.382 in N/A 4-1/8 in
HCN15000XXX N/A Hex Coupling Nut, 1.5000" Nominal Dia. N/A 1-1/2 in N/A 2-1/4 in N/A 2.598 in N/A 4-1/2 in
HCN16250XXX N/A Hex Coupling Nut, 1.6250" Nominal Dia. N/A 1-5/8 in N/A 2-9/16 in N/A 2.959 in N/A 4-7/8 in
HCN17500XXX N/A Hex Coupling Nut, 1.7500" Nominal Dia. N/A 1-3/4 in N/A 2-3/4 in N/A 3.175 in N/A 5-1/4 in
HCN18750XXX N/A Hex Coupling Nut, 1.8750" Nominal Dia. N/A 1-7/8 in N/A 2-15/16 in N/A 3.392 in N/A 5-5/8 in
HCN20000XXX N/A Hex Coupling Nut, 2.0000" Nominal Dia. N/A 2 in N/A 3-1/8 in N/A 3.608 in N/A 6 in
HCN22500XXX N/A Hex Coupling Nut, 2.2500" Nominal Dia. N/A 2-1/4 in N/A 3-1/2 in N/A 4.041 in N/A 6-3/4 in
HCN25000XXX N/A Hex Coupling Nut, 2.5000" Nominal Dia. N/A 2-1/2 in N/A 3-7/8 in N/A 4.474 in N/A 7-1/2 in
HCN27500XXX N/A Hex Coupling Nut, 2.7500" Nominal Dia. N/A 2-3/4 in N/A 4-1/4 in N/A 4.907 in N/A 8-1/4 in
HCN30000XXX N/A Hex Coupling Nut, 3.0000" Nominal Dia. N/A 3 in N/A 4-5/8 in N/A 5.340 in N/A 9 in
HCN32500XXX N/A Hex Coupling Nut, 3.2500" Nominal Dia. N/A 3-1/4 in N/A 5 in N/A 5.773 in N/A 9-3/4 in
HCN35000XXX N/A Hex Coupling Nut, 3.5000" Nominal Dia. N/A 3-1/2 in N/A 5-3/8 in N/A 6.206 in N/A 10-1/2 in
HCN37500XXX N/A Hex Coupling Nut, 3.7500" Nominal Dia. N/A 3-3/4 in N/A 5-3/4 in N/A 6.639 in N/A 11-1/4 in
Unit of Measure
1 2