b'The requirements vary greatly based on the size of the plane,the load and stress of a mating section and the manufacturer.Fastened for Flight Whatever the method, a backing bar or similar type of supportusually placed on the inside of an aircraftoften is needed to keep aircraft skin from deflecting Several methodologies exist, but the most preva- during drilling. In other instances, two or more sections lent is the use of a power drill and spring-loaded mi- of material may need to be disassembled, cleaned, de-crostop, also known as a microcage, said Linn Win, se- burred and then reassembled before rivet installation. nior business development manager at OSG USA Inc.,Compared with chamfering a hole in a machined part, Irving, Texas. The cutting tool itself is typically a pi- countersinking fasteners on an aircraft fuselage is com-loted 100 or 130 countersink with a threaded shankplex work.that screws into the microstop. You set it to the desiredThese operations are made even more complex depth, place the tools pilot into a pre-drilled hole, en- by the fact that aircraft-makers use a wide range of gage the drill motor and then push down to produce the countersink.He described a few methods that are more pro- about the author ductive.Oneistouseasemi-automateddrill- Kip Hanson is a contributing writer for ingunit,whichcandrillandcountersinkinasin- CTE. Contact him at 520-548-7328 or gle-shot operation. Also, robotic and fully [email protected] not only accurately countersink a hole but in-stall a rivet, commonly known as drill and fill.Countersinking.indd 29 4/16/20 4:58 PM'