Usenet Nutter wrote:
On Sat, 27 Feb 2010 11:47:14 -0000, "Grumps"
wrote:

Hi

I have a need to screw into some sheets of acrylic. I have some 1/2" #6
screws. I believe this is 3.5mm in metric speak. But is that the hole size I
have to drill?
Ta.


Dunno what the right answer is but make sure you choose carefully
otherwise you'll get the dreaded "Spider Web" result

test on scrap.

acrylic is quite decent to tap. so a drill slightly bigger than the
inner shank, but smaller than the exterior thread diameter, is indicated.