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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)

HCN40000XXX N/A Hex Coupling Nut, 4.0000" Nominal Dia. N/A 4 in N/A 6-1/8 in N/A 7.072 in N/A 12 in
HCN42500XXX N/A Hex Coupling Nut, 4.2500" Nominal Dia. N/A 4-1/4 in N/A 6-1/2 in N/A 7.506 in N/A 12-3/4 in
HCN45000XXX N/A Hex Coupling Nut, 4.5000" Nominal Dia. N/A 4-1/2 in N/A 6-7/8 in N/A 7.939 in N/A 13-1/2 in
HCN47500XXX N/A Hex Coupling Nut, 4.7500" Nominal Dia. N/A 4-3/4 in N/A 7-1/4 in N/A 8.372 in N/A 14-1/4 in
HCN50000XXX N/A Hex Coupling Nut, 5.0000" Nominal Dia. N/A 5 in N/A 7-5/8 in N/A 8.805 in N/A 15 in
HCN52500XXX N/A Hex Coupling Nut, 5.2500" Nominal Dia. N/A 5-1/4 in N/A 8 in N/A 9.238 in N/A 15-3/4 in
HCN55000XXX N/A Hex Coupling Nut, 5.5000" Nominal Dia. N/A 5-1/2 in N/A 8-3/8 in N/A 9.671 in N/A 16-1/2 in
HCN57500XXX N/A Hex Coupling Nut, 5.7500" Nominal Dia. N/A 5-3/4 in N/A 8-3/4 in N/A 10.104 in N/A 17-1/4 in
HCN60000XXX N/A Hex Coupling Nut, 6.0000" Nominal Dia. N/A 6 in N/A 9-1/8 in N/A 10.537 in N/A 18 in
Unit of Measure
1 2