I attempted to make a MagSafe 2 to MagSafe 1 converter. It might be easier to just grind a MagSafe 2 plug, make it narrow enough to fit into a MagSafe 1 inlet receptacle.
Later addition: it is not worth making a MagSafe 2 to MagSafe 1 converter. It is not as useful as a MagSafe 1 to MagSafe 2 converter. If you decide to file or grind your own, then be careful: if you work too quickly, then your plastic might melt.