Aircraft Drill Accessories

Key accessories for aircraft drilling include drill bits, countersink cage, countersink bits, drill guides, drill stops, and a de-burring bit.

Standard wire gauge drill bits are #40 (3/32”), #30 (1/8”), #21 and #10. These bits will drill the holes for most standard aircraft fasteners. It is recommended to have a full set of 60 wire gauge drill bits just to have the exact size needed for any critical holes you may need to drill. Generally 3” to 6” drill bits are standard for most drilling applications. Occasionally you may find a need for a 12” long bit in the #40 and #30 sizes for hard to access areas. On ¼-28 threaded bits for the angle drill the #40 and #30 are generally the sizes needed. You will find that spring type drill stops are great to keep from damaging your skin and parts – you won’t need to worry about the drill chuck marking the aluminum.

A countersink cage with 1,000th adjustment increments is perfect. Ball-bearing types are preferred. You will need 100-degree (aircraft standard) countersink bits with pilots that match the drill bits in #40, #30, #21 and #10 sizes. Countersink bits need to run at a high-speed in order to cut a clean neat countersink. Adjust the countersink using a piece of scrap metal and test the fastener fit to get it as flush as possible before countersinking you airplane skins.
Drill guides are needed if you have holes that need to be perfectly straight. These are generally plastic guides with a metal collet that matches the drill bit diameter. Rest the guide on your part and drill straight through.

A de-burring bit will make it easy to remove burrs from the holes (although I prefer the hand type speed de-burring tool that uses the countersink bit to de-burr. See the link above.