G’day; Ok, so ankles are variable in diameter. Some folk suffer from
fluid retention and the diameter of my ankle, for instance changes
all the time. So if a chain is to be made for a certain person (NEVER
a girl; ALWAYS a young woman if your client is the female of the
species 
why not do the time honoured ritual with a length of soft
copper wire, wrap it around the ankle until it’s owner cries, “Stay;
enough” or words to that effect, twist the wire so it is right, then
cut it off with nippers. (the wire, not the ankle) Lay the wire on
your bench, straightened and that is the right length. You may
however want to add the odd link - but don’t tell her that. – Cheers
now,
John Burgess; @John_Burgess2 of Mapua Nelson NZ