how is the iron blade int he tools used to dig soil fixed to the wooden stick

Iron blade is always made smaller in size to fix inwood. Iron is a metal all the metals have property to expand and contract expansion means to become larger in size and contraction means to become smaller in size expansion takes place when iron is heated and iron also become softer after being heated and then when it is fixed in word we can apply cold water to it and this will make that iron to contract and it will fix in the wood handle tightly