# 37Â° & 45Â° Flared Fittings



## Skybolt540 (Oct 31, 2011)

The following isa letter I received several years ago from Parker Hannifin in response to an inquiry I had regarding the application and use of37Â° and 45Â° fittings. Thought others might find it of interest.

_The 45 degree flare fittings (SAE J513) were developed for the refrigeration applications in the mid thirties. Because of the low pressures involved in these applications, annealed copper tubing was predominantly used. This tube is well suited for the 45 degree flaring. Over the years, these fittings have found other low pressure applications in automotive and other industries. They are also used, currently, with thin wall annealed low carbon steel tubing._



_The 37 degree flare fittings were originally used on aircraft. At the time these were considered high pressure fittings, used with stainless steel and carbon steel tubing. The higher strength, harder, tubing of the time was difficult to flare without the tubing cracking. Therefore, a smaller flare angle was chosen ( 30 degrees initially and changed to 37 degrees later). These were then standardized as JIC and SAE J514, eventually, for the industrial use._


_Thus, we now have the 45 degree flare fittings for low pressure applications and 37 degree flare fittings for the high pressure ones._


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