Wooden handle, idea for file, BBQ skewer handle.
Made from wood with a metal collar (Collar retains the wood in the end of the handle and helps prevent the wood from splitting when tongue is driven into the end). 

5pc-pack Wooden handle 6mm center hole 130mm length, suitable for 8".10" files, the biggest OD is 30mm

5pc-pack Wooden handle 8mm center hole 130mm, suitable for 12", 14" files, the biggest OD is 31mm