Most homebuilders have experienced the struggle to properly clock AN fittings that penetrate bulkheads and the firewall. Murphy’s Law rules as we try and point 90-degree fittings properly on both sides of a penetration, yet the torque keeps coming up short. And sometimes, special situations require the use of different types of fittings on either side of the bulkhead—fittings which simply don’t exist, no matter how many times you peruse the Internet and catalogs.
Cleaveland Aircraft Tool comes to the rescue with the Howe Fitting—a bulkhead penetration that screws into either side of the firewall, tank skin, or web and allows any standard AN pipe-threaded fastener to be screwed into either side. Need a 90-degree elbow on one side and a straight fitting on the other? No problem—just screw them in. How about a beaded pipe for attaching a soft hose? Again, the pipe-thread portion will screw right on—no matter if you need it straight, 90, or even 45.
The Howe fitting was designed by California builder and machinist David Howe and is manufactured by Cleaveland. It consists of two pieces: the bulkhead penetration and the nut that screws on the other side. It leaves you with a female pipe thread on both sides that can accept whatever you have to assemble. This allows custom and convenient configurations to be used and can simplify hoses and plumbing by giving you exactly what you need—not just what the AN catalog can provide.
Cleaveland recommends mounting the Howe Fitting with a (supplied) .015-inch stainless steel washer to stiffen the firewall or bulkhead and tighten things up. They work great for all of the fluid and instrumentation penetrations necessary on a firewall or fuel tank.
The Howe fittings are available in ¼-inch NPT or 1/8-inch NPT sizes and come blue anodized, just like standard AN fittings. They are manufactured from 6061-T6 aluminum. The ¼-inch size mounts in a 7/8-inch hole, while the 1/8-inch size uses a 5/8-inch opening. Both can be used on bulkhead thicknesses from 0- to 5/16-inch.
For more information, go to www.cleavelandtool.com.
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The long end, the end that is inserted through the bulkhead, should have flats on the outside for holding while the npt Fitting is torqued/clocked.