CA4004-6 Industrial Back Countersink (California Aircraft Tool) delivers a precise 100° back-counterbore countersink with a 3/8" body diameter and a 3/16" pilot. Designed for back-side countersinking in restricted-access areas, it enables flush-head rivets and clean countersunk pockets on aerospace sheet metal. The 3/8" diameter and 100° angle produce the standard back-counterbore geometry used in aviation tooling, while the 3/16" pilot aligns with common hole sizes for rivet applications. This countersink is intended for use in aerospace maintenance and fabrication tasks where access from the opposite side is limited and a consistent countersink depth is required.
