Originally Posted by DesktopDoctorNZ
And yes I've ordered 2 x
Bitspower G1/4" Female / Female Pass-Through Fitting / Fillport.
I just don't know what size to drill. Somewhere said 16mm and somewhere said 9 and now 10... Lol help would be greatly appreciated
I'm assuming you mean this piece
Interestingly, it is listed as having a G3/8" outer thread on frozencpu's site, but Bitspowers' own site lists it as having
an M20 outer thread here
(same part No., BP-MBWP-C04).
I'm not sure if there's something I'm overlooking. In any case, the G3/8" outer thread has an outer diameter of 16.662 mm
according to this site
If it's an M20 thread, you'll probably need a 21 mm dia hole (I'm guessing it will be a fine thread, if it's a medium M20
you'll need a 22 mm hole, and if it's a coarse thread 24 mm, but it doesn't look like that on the pics).
I'd recommend waiting until you get the parts and then doing your own measurements. In any case, while 3/8" is ~9.5 mm,
a G3/8" thread is substantially larger than that. I think the thread size originally referred to the pipe's inner diameter which
would be used with a corresponding fitting. So a G3/8" fitting would have been used with a pipe of inner dia 3/8", and therefore
the fitting itself would have needed to be a tad larger. I don't think it translates like this anymore today though, it's just
how things developed historically.