While reading about machine-lubrication equipment I came across information about a banjo bolt, also known as a banjo fitting, which was new to me. I’ve included a photo below that illustrates the two main components–the banjo bolt and the inlet ring, plus two washers. Apparently automobile brakes use banjo bolts to connect brake-fluid lines to brake cylinders. I don’t rebuild car brakes, so I never discovered this somewhat-common component.
In a design, a washer goes onto the bolt, followed by an inlet ring, followed by a second washer. The inlet ring has a concave space around the inside perimeter, so the inlet hole need not align with the hole into the center of the bolt. Tightening the bolt provides a path for fluid to flow into the barbed inlet into a hole in the side of the bolt and then down through a hole concentric with the bolt’s axis. The flow seems easy to follow.
Courtesy of True Asset Renewables.
I wonder, though, why go to all the trouble to use a banjo bolt when a compression fitting such as the one shown below would do the job?
Courtesy of Swagelok.
Perhaps engineers and mechanics don’t like the the possibility of over-compressing this type of fitting, but it seems much simpler to me. A banjo bolt, however, provides more flexibility during alignment because you can position the inlet ring at any angle. An angled compression fitting screws into mating equipment and takes on a fixed position. Or, the tubing must connect perpendicular to the equipment.
I welcome thoughts on banjo bolts or fittings vs. compression fittings and the pluses and minuses of each. –Jon Titus
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