In the other countries，in order to keep the beauty of iron craftwork，the welding joint is  stamped with the bayonet，however,the material of bayonet with two ways of tongue and   groove steel，this machine can coldly roll this kind of steel with 20mm *1.5mm into tongue and  groove deducted card by manually operation，after cutting short，the " ”form of pattern bender  can be used in iron craftwork .