The fastener sleeves and grommets specified herein are intended for structural and non-structural application in aerospace structures and other military equipment. The function of the sleeves and grommets is to serve as a repair method for holes that have become damaged, elongated, or corroded, and to protect the structure in soft or brittle material. The sleeve is intended to increase the integrity of the overall joint, not the strength of the individual fastener.

Length adjustment.

Fastener sleeves and grommets that are manufactured with proper head configuration and diameter may be procured at the required length. Alternatively, sleeves may be adjusted to the correct length for each individual fastener.

Installation of sleeves and grommets.

Fastener sleeves and grommets should be installed with reasonable care to ensure that they seal properly, inhibit corrosion, and establish, preserve, or restore the structural integrity of joints in modification, repair, or in the original manufacture of aerospace or military hardware. The installation information and the processing specifications should be followed. Tools are available to facilitate and ensure proper installation of the sleeve or grommet.

General purpose and restrictions.

The fastener sleeves and grommets will be used to replace oversize shank fasteners for repair and maintenance. The sleeves and grommets will be used with standard diameter straight shank fasteners. They will be used under the same restrictions as oversize fasteners and in compliance with the specific user's repair procedures and restrictions.

Number of fasteners.

There will be no restrictions on the number of fasteners installed with sleeves or grommets when the edge distance from the center of the hole is two times the diameter and greater.

Fasteners.

The fastener or attaching element (nut or collar) will contain a counter-bore to accept the protrusion of the sleeve or grommet; or a washer will be used; or the sleeve or grommet will be flush on the backside of the stack.

Fastener restrictions.

The fastener sleeves or grommets will not be used with tapered shank fasteners or blind fasteners.

Interference. Interference (hole-to-sleeve) will be not greater than 0.003 inch where the material thickness is less than 0.5 inch. Interference will be not greater than 0.0015 inch where material thickness is greater than 0.5 inch.

Applications.

Appropriate engineering approval will be required in the following applications:

a. In fluid containers having no self-sealing feature, as in fuel, oil, or water tanks.

b. Fatigue and fracture critical locations.

c. Where the edge distance from the center of the hole is less than 1.5 diameters.

d. Where the number of discrepant holes being repaired is greater than 10-percent of the total number of holes in a pattern.

e. Where more than three adjacent holes are discrepant.