Lot Essay
The screw taps conform to no recognisable standard, but similar threads have been encountered in metal musical instruments, particularly banjos and flutes.
Details
A Holtzapffel universal cutting frame (as Vol V fig 135) -- 9/16in. x 3/8in. shank; a horizontal cutting frame --¾in. square shank; and a set of ten handled screw taps from .086in. x 36 TPI to .210in. x 26 TPI, in ebonised beefwood handles. (12)