Fastener Substitution NAS 1008
Fastener Substitution NAS 1008
(OP)
We are looking to replace fastener NAS1008 1/2"-20, CRES, A-286 (UNS S66286) per AMS 5731, 140,000 PSI Min. These are used in wetted military marine environment, where galling, cross threading and fouling is a problem. We would consider a material substitution in the similar strength, and corrosion resistance (Inconel 686, ect). We are looking for a specification or recommendation for 1/2"-13 coarse thread fasteners.





RE: Fastener Substitution NAS 1008
Why are you changing these if it is a military application and the screws are specified?
RE: Fastener Substitution NAS 1008
RE: Fastener Substitution NAS 1008
A couple of questions for you...
1) Do you absolutely have to use a standard military/aerospace fastener like NAS, etc. or can it be a custom manufactured part?
2) Quantity needed?
3) When you say "fouling from salt", does this include actual corrosion (red rust, etc.) during use? Are the fasteners disassembled and reassembled often?
4) What are the mating internal thread details (material, coating, etc.)?
In general, changing from fine to coarse thread will improve the galling and cross-threading situation. Are you using any type of lubricant during assembly? This is an absolute must for stainless steels and nickel alloys, especially if you are trying to generate high clamp forces by using high assembly torque.
RE: Fastener Substitution NAS 1008
Each assembly uses 1000 of this fastener. Fasteners are typically removed every few years. They go through an aluminum extrusion, providing a clamp up. I have seen salt and aluminum byproducts on the threads. They are installed dry torque to 600 in-lb.
RE: Fastener Substitution NAS 1008
RE: Fastener Substitution NAS 1008
RE: Fastener Substitution NAS 1008
Ended up with specifications:
ASME Specification ASME B18.2.1
ASTM Specification ASTM A453 Grade 660