The tie down brackets come as aluminium extrusions with a hole in them. The hole needs to be tapped to accept a 3/16" screw thread, as on the forged steel tie-down rings that will eventually protrude from the underside of each wing.
Avery provided the tap, and whilst I do have a tap handle it is a flimsy and insecure-feeling bit of cheap Taiwanese crud, so I splashed out on proper T-handle. As it turned out, that was only a fiver from Amazon - so very pleased.
Into the vice goes the bracket, and the handle is turned 1/2 a turn before turning 1/4 turn back to break off the swarf, and repeat until 1" depth of the hole has a thread.
Turning back 1/4 turn is essential; I still have strong memories of breaking a tap off in the hole during school metalwork classes at age 14, because I just kept turning the tap.
Finally today I spent 20 minutes finshing off deburring the main LH wing ribs. Only another 36 more to do: 14 more for the LH ribs and then all the nose ribs!
