Never use an ________ flaring tool which produces a flare of 45 degrees.

Using an automotive type flaring tool that produces a flare of 45 degrees is discouraged because most fluid lines used in hydraulic and pneumatic systems require a specific flare angle for proper sealing and performance. Typical standards for flaring in these applications call for a 37-degree flare, particularly with AN (Army-Navy) fittings. A 45-degree flare can lead to leaks or improper fittings, which can compromise the integrity of the fluid system.

Automotive flaring tools are often designed with the 45-degree flare for applications like fuel and brake lines in vehicles, making them unsuitable for industrial or hydraulic applications that demand a more precise fit and superior sealing capabilities. Therefore, avoiding the use of an automotive type flaring tool is crucial to ensure safety and functionality in fluid systems.