dowel pins & corresponding drill sizes to get a tight fit....

[HankMcSpank]

I need to use some 1.6mm stainless steel dowel pins ...these will fit into some 1.6mm holes drilled into acrylic by my cnc machine.

Problem is, at the moment is that a 1.6mm dowel pin, fits a bit too loosely into a 1.6mm hole (don't get me wrong it's actually a 'neat' fit, but I really seek a solution where I have to gently tap the dowel pin into the hole with a small hammer - at the moment I'm having to superglue the pins to hold them in place in the acrylic (!), but that's not ideal as there's little for the glue to key into & the pins can still work loose)

So what's happening here?

Is this because the 1.6mm drill is out of spec, or perhaps the drill has melted the acrylic a tad, resulting in a slightly oversized hole?

I can actually source 1.65mm pins, but then wonder would these even fit into a 1.6mm hole?!! (or is it normal to buy slightly oversize pins to overcome this problem?)