The process is simple. Flame cut the horn to a square or octagonal pyramid and machine the taper.
Setup for machining can be done on an angle block OR a special fixture as shown.
The fixture as shown is horizontal on a lathe but could also be used vertical on a turret lathe or vertical boring mill.
This would be the preferred method for production turning large anvils.
A combination fixture could easily be used to machine four different sizes of anvil without changing the setup.
A similar setup is used for belt grinding cast or forged conical anvil horns.
This could be done on a machine tool OR a rotary weld positioner.
The belt grinder is supported at the correct angle on a swing arm and only takes seconds to do its job.
Anvil made by BurntForge
Italian style fabricated anvil with example of turned horn.
Details . . .