This is offered as a resource to address an assembly of common questions related to Inch Locknuts.  The development and evolution of Imperial Locknut specifications has opened the door to questions we will try to answer here.

IFI 100/107 is replaced by ASME 18.16.6 - 2022
Initially, locknut requirements were defined by agreement between manufacturers and end users.  The lack of a consensus standard for locknuts motivated the Industrial Fasteners Institute to work with manufacturers to develop IFI 100, published in 1967 for hex locknuts, and IFI 107 in 1969 for flange locknuts, the two were combined in 1987.  IFI 100/107 underwent several revisions over the years, most significantly in 2002 when the prevailing torque requirements were changed from 5th removal to 3rd removal.  In 2014 ASME published 18.16.6 to replace IFI 100/107 as a comprehensive locknut specification covering inch sizes of all-metal and nylon insert locknuts.

Common Q & A about Aztech Inch Locknuts and Documentation

1. Q)  Why are dimensional requirements we see on Aztech Inspection Certificates sometimes different than those on Aztech Drawings?
   A)  The dimensional requirements used on Aztech Inspection Certificates reflect the sometimes excessively generous thickness requirements of the Consensus Specification, the Aztech Drawing will reflect the tighter thickness tolerance to which the parts are manufactured (maintaining compliance with the Consensus Specification).  Upon request, the inspection certificate can reflect the Aztech Drawing limits, and will cite the drawing as the specification source.  We can’t cite a consensus standard as the dimensional requirements source without reporting the limits per that standard.
2. Q) Why are flange nut dimensions different between free-spinning flange nuts and flange locknuts?
   A) For an unknown reason, during the historical development of the specifications for the free-spinning flange nuts and flange locknuts, the dimension limits were not aligned with each other and the conflict carries on today for a limited number of sizes, (1/4”, 3/8”, and 5/8”).
3. Q) Why are the Aztech part numbers for Grade F Flange Locknuts out of sequence for sizes 1/4” through 5/8”? 
   A) Decades ago the free-spinning flange nut dimensions were used exclusively for Grade F locknuts among the Aztech customer base and we set up our numbering system to reflect this.  More recently, we have seen the market move to comply with the locknut standards for dimensions but we could not change the original part numbering sequence for existing business.
4. Q) Why do some of the Aztech web site drawings indicate compliance to ASME 18.16.6, and the Aztech Material Certification for the same part indicates compliance to IFI 100/107?
   A) Aztech Quality Assurance and Product Engineering are systematically updating web drawings and part routings to reflect the new IFI 100/107 replacement spec, ASME 18.16.6.  Until this update is completed, there may exist times where the drawings and certs for the same part point to different (but nearly identical) consensus standards.