NAS43 Sleeve Spacers

NAS43, titled "Spacer, Sleeve - Screw and Bolt," is a National Aerospace Standard published by the Aerospace Industries Association. The part is a plain tube with square ends and no flange. It slides over a fastener shank and keeps two assembled parts a set distance apart. The standard covers bolt and screw sizes from .112 inch up to 1.000 inch, with lengths set in 1/64 inch steps. The Department of Defense adopted NAS43 in December 1993, and the parts fall under federal supply class 5365.

HOW TO READ A NAS43 PART NUMBER

A NAS43 part number has four pieces: the material code, the diameter code, the length dash number, and a finish code when one is required. The material code comes right after "NAS43." DD means 2024-T aluminum alloy and HT means heat treated alloy steel. The first number is the diameter code, which matches a row in the standard's table giving the bolt size, OD and ID. Diameter -2 is inactive. The second dash number is the length in 1/64 inch. On aluminum parts, N means grey anodize and FC means chemical film. A means unfinished. Worked example: NAS43DD3-48FC is a 2024 aluminum spacer (DD) for .164 or .190 screws (diameter 3: OD .302 to .322, ID .194 to .234), 48/64 = .750 inch long, with chemical film finish (FC).

MATERIALS AND FINISHES

DD spacers are 2024-T3 aluminum tubing to AMS-WW-T-700/3 or 2024-T4 rod or wire to AMS-QQ-A-225/6, with a 62,000 psi minimum tensile strength. They come grey anodized to MIL-A-8625 Type I (code N) or with chemical film to MIL-C-5541 Class 1A, dyed blue (code FC). HT spacers are 4130 or 8630 alloy steel heat treated to 125,000 to 145,000 psi, cadmium plated to AMS-QQ-P-416 Type II Class 2 and dyed iridescent bronze. Code A parts are unfinished, and unfinished alloy steel parts get a light coat of oil. Every order ships with CofC and lot traceability.

SUPERSEDING SPECIFICATION

NAS43 is active at Revision 12, dated November 30, 2012, and has not been superseded or cancelled. Within the standard, diameter -2, low carbon steel and normalized alloy steel spacers are inactive for new design.