Boiler tube expander marked with a broad arrow. . Metal working tool. Consists of a metal core, tapered. Has a distinct head with two holes bored through it, one through its diameterm, one across . A detachable collar fits round this. Centre part of which rotates and has four metal washers above it, collar ends with three shaped upstanding pieces which hold three cylindrical rods. Thick washer fits on end of this and screws into the collar (no screws).