Partway through making a rear toolpost I had finished some of the milling and next day decided to turn the holding down bolts 2 off 75 mm long 10mm dia. Before starting I thought better check I've got 10mm die, no, after searching through several drawers. Obvious choice is turning but with the abortion of the change gear set up banjo it can become a lengthy process. (I'm also in the middle of making revamped version)
As the thread type wasn't that important I'll go with 3/8 BSF. Check BSF tap draw, yes but only 3, check for 3/8 die, yes safe to go ahead. Bolts made and back to the mill to drill and tap the base. I hadn't really looked at the taps except to make sure they were the correct size. 2 nackered 1 st taps and a plug. First taper tap managed to put a chamfer at the top of drilled hole nothing more. Onto the next tap which did at least make a couple of turns, used the plug tap another 2 turns. Alternating between these two the holes were finally finished. How long did it take? I don't know my brain went numb.
Where do the RAF come in well hopefully the photo will show the tap clearly but was Air Ministry supplied in 1939.