Two piece firewall shield, 1/2-Inch hole and 3/4-Inch dimple for grommet.
Two piece shields for use over cables or wires with large end-fittings or existing installations. Single piece for use where the cable or wire may pass through the hole. Flat shields designed for use on wooden or composite firewalls using a fire resistant sealant to prevent leaks. Both types of shield available in flat or with dimple to accommodate rubber grommets up to outside diameter. Actual hole size in 2 piece shields is slightly larger than indicated to prevent chafing cable. Ream pilot hole in single piece shields oversize for the size grommet used. Use grommets that fit tightly around the cable or wire to insure a good seal. Shields may be installed with screws, bolts and plate nuts or rivet nuts. Install cable and grommet in firewall. Locate the shield to insure that it is centered on the cable - then drill attach holes in firewall. Shields predrilled with 5/32” mounting holes. If more than one cable passes through grommet fire resistant sealant must be applied to grommet.
**Caution: Any holes drilled in the firewall are potential source of carbon monoxide in the cockpit. Extreme caution must be exercised when installing firewall shields in your aircraft. They do not provide the nec essary seal around cables or wires to prevent carbon monoxide, smoke or fire from entering the cockpit. The shields are designed only to protect the sealing material (grommets/gaskets) from excessive heat.
I used these on both sides of the firewall, and they covered the grommet perfectly. I like the split design which allowed me manipulate the wires and final position of the grommet while still having one half of the shield in place.
These are stainless steel fire shields.
2-1/4" from center to center.
These are commonly sold with AN931-5-12 which would give you a 5/16 hole.