i was thinking to try with an arbor press.
~
In praticular i would like to know if a 1 tonn press would be enough.
I haven't tried it, but my gut feeling tells me 1000 kg on a metal letter stamp isn't going to make a dent.~
In praticular i would like to know if a 1 tonn press would be enough.
i'm using a 0.5kg hammer
Get a bigger hammer 
Hit it with 1 kg.I Googled a bit: different sites have different numbers, but it looks like the force of a hammer hit on steel can be 10 tonnes.