I dont use small as in 2.5mm punch pliers, for that size hole I
would use the Roper whitney tool or 1 ton fly press.
However, the problem is that the pliers you describe are most
probably badly made…
To explain why.
In any punch and die setup the punch is normally parallel and the
die is also parallel for the 1st 2 mm then it tapers away toward the
die bottom so that as the punch pushes the cut metal through the
parallel part then is free to fall away once the die is bigger than
the punched metal.
This is obviously not the case in the Lindstrom 2.5mm hand tool you
sent back. They are probably a far eastern copy of the genuine
Swedish made tool.
This punch and die principle is universal to what ever size your
punching, wether its 2.5mm hole or like me a rectangle buckle back
some 4in by 2.5in on a 10 ton fly press out of 1/10th in brass.
You will need to get a GENUINE Roper Whitney hand tool, wether your
strong enough to use it is another matter.
For one operation I welded a 1 by 1in leg on to one of my RW tools
and hold in the leg vice with extensions on the top handle to punch
through some stainless steel. After 45 yrs of hard hand work ive worn
out the catilage in my thumb joints so cant grip like I used to!