this is the way i make them
First up the material used is 0.1mm brass sheet this isn't the norm but you will need to guage the thickness for your own needs
the bigger the hatches/door the thicker the sheet and tube/rod the thickness of the former (rod/tube) depends on the size of the original
next is to measure the hinge to be replaced
then look at the original and see what it looks like and what type your going to build (this one has a 3 position hinge similar to a door hinge)
measure the hinge and transfer it to the brass sheet and cut out the strip you'll need two strips for one hinge
fold the strip around your rod/tube and clamp firmly with pliers creating the nice round
tube
More to follow