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Automotive Fittings Explained

By Jason
1 year 2 months 1 day ago
IFF and IFM

These are some common terms used in the industry when discussing brake fittings. IFF - meaning “Inverted Flare Female” and IFM - meaning “Inverted Flare Male”. The diagram to the right illustrates the two most common types of fittings used in a typical Street Rod brake system. The first is the inverted double flare, used by most domestic production cars and trucks. It uses a 45* double flare to seal, which has tubing that is folded over into itself before flaring outward. On the right, is a 37* single flared line with a tube sleeve and coupler that allows you to adapt to AN fittings.

3/16-inch tubing is one of the most common sizes used in brake systems, which makes use of a 3/8-24 inverted flare nut like part number 91031820. When using 1/4-inch brake tubing, a 7/16-24 inverted flare nut is used, like part number 91031819.

AN Fittings

AN fittings, also known as Army/Navy, were originally developed as a military standard that dates back as early as World War II. A fitting listed at – 3 (dash three) refers to the inside diameter of the fitting, for instance a – 3 AN would fit a metal tube outside diameter of 3/16-inch. You will also notice that the size increments are 1/16-inch apart. All of the AN fittings that Speedway offers will feature a 37* tapered flare. The chart to the right and below will show some of the common AN sizes along with the closest national pipe thread size (NPT). Note that AN fittings and NPT fittings will not work together.

NPT

National Pipe Thread is a tapered machine thread for threaded pipes and fittings . NPT threads can be referred to as “Male pipe thread” or “Female pipe thread”. This common thread can be found on a wide variety of applications from natural gas pipes, plumbing fixtures, hydraulic lines and hoses, and even your car. We use these in the Street Rod and Racing industries for fluid fittings such as oil lines, brake lines, and coolant lines. NPT threads are tapered to create an interference fit and often use thread tape or thread sealant to form a liquid tight seal without the use of crush washers, O-rings or gaskets. NPT fitting sizing does not refer to the physical dimension of the threads. The sizing chart is in reference to the inside diameter of a schedule 40 black iron pipe. Example: a ½ NPT thread has an outside diameter of approximately .840” (at the small end of the tapered thread).

Common Fittings used on a Street Rod

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