circle cutting - not quite there yet...

I have invested in a new metal circle cutter - when I say new... I mean an ancient, really old school manual circle shear (a bit like a tin opener on steroids...) It is supposed to speed up the process of cutting copper circles ready for spinning. Currently, I cut everything by hand with a pair of snips.  However, it arrived ancient, greasy and dirty - none of which I would have minded (too much) except that it also didn't work.  These are my first attempts to cut some aluminium and some copper.  Don't be fooled by the aluminium circles - they were precut ones I bought and was practising on.  Something is wrong with the clamping mechanism - I'm hoping that it can be sorted out...