Interpretation ID: nht92-7.11

DATE: May 8, 1992

FROM: Paul Jackson Rice -- Chief Counsel, NHTSA

TO: J.W. Lawrence -- Volvo GM Heavy Truck Corporation

TITLE: None

ATTACHMT: Attached to letter dated 10/25/91 from J.W. Lawrence to NHTSA Administrator (OCC 6634)

TEXT:

This responds to your letter of October 25, 1991 requesting information on whether metric sizes and threads for attachment bolts would be considered "equivalent hardware for the requirements of S4.1(f) of Standard No. 209, Seat Belt Assemblies. In general, it is permissible to use metric hardware for the installation of safety belts. However, as explained below, it is unclear whether the metric fastener M12, as described in your follow-up letter of December 13, 1991, is equivalent to the attachment hardware specified in Standard No. 209.

The Department of Transportation is implementing the policy of using metric dimensions, in addition to American Standard dimensions, in our regulations. Currently, FMVSS No. 209 "Seat Belt Assemblies," requires the safety belt anchorage bolt to be

"7/16-20 UNF-2A or 1/2-13 UNC-2A attachment bolts or equivalent hardware" (S4.1.(f)).

The SIZE of the bolt specified in your letter is equivalent to the safety belt anchorage bolt specified in Standard No. 209. Since the M12 nut is approximately halfway between a 7/16 and a 1/2 inch bolt, it is clear that the size would fulfill the requirement of the standard. However, it is not clear from the information provided, whether the class of thread fit of the metric bolt is comparable to the requirements of the standard. The standard does specify a Class 2 bolt. A Class 2 thread provides clearance under all conditions and allows external threads to be plated with no resultant assembly difficulties. This is the most common commercial grade fit. Therefore, if the bolt thread fit is equivalent, we would consider this metric bolt to be equivalent hardware to the bolt specified in Standard No. 209.

I hope you find this information helpful. If you have any other questions, please contact Mary Versailles of my staff at this address or by phone at (202) 366-2992.