local reg_coil = function(name, mat)
    local coil_id = terumet.id('item_coil_'..mat)
    minetest.register_craftitem( coil_id, {
        description = name,
        inventory_image = terumet.tex(coil_id)
    })
    local ingot_id = terumet.id('ingot_'..mat)
    minetest.register_craft{ output=coil_id .. ' 3',
        recipe = {
            {ingot_id},
            {ingot_id},
            {ingot_id},
        }
    }
end

reg_coil('Pure Terumetal Coil', 'raw')
reg_coil('Terucopper Coil', 'tcop')
reg_coil('Terugold Coil', 'tgol')