Tap seat grinding tool. Spring holds cutter in contact with the tap seating. Cutter with serrated underside, screws on to cutter-holder.
M7 thread. Taper ensures a correct fit on the head of the tape.
Cutter-holder no.1 : internally and externally threaded tapered cone.
Cutter-holder no.2: triple cone: for servicing of bath, basin, kitchen and bib taps.