Drilling Through a PCB

Thread Starter


Joined Apr 16, 2018
I am new to this forum and I have a small question. I am planning to build a project in which PCBs are used as structural elements (not too much pressure is put on them so that’s fine) but I am wondering if drilling an M3 hole in the board where there are no traces could work to run through some bolts to attach another part of the project. Would drilling snap the board or break the bit or for such a large but should it work fine.
Thanks a lot for all of your help,


Joined Mar 30, 2015
Welcome to AAC!

Can't say for certain without knowing the board material or thickness.

If you have enough material around where the hole will be drilled, there should be no problem with the board snapping. I've drilled CEM-1 PCB and used #6 (about the same diameter as M3) hardware to attach to boards for school science projects and didn't experience any breakage.

Breaking drill bits should also not be an issue; especially if you use a drill press.


Joined Jun 4, 2014
If this is normal PCB material (FR2 or FR4, 1.6mm thick) then drilling a 3mm hole would not cause any problem. A normal HS steel bit will do the job but if the board is fibreglass then it won't drill too many holes before becoming blunt as fibreglass wrecks tools. Carbide tools are used if many holes are needed.


Joined Aug 7, 2008
'Not sure what a M3 hole is but a hole of any diameter could be drilled with right bit. Pilot hole
successive larger bits, tapered reamer, etc.

Thread Starter


Joined Apr 16, 2018
Thanks all for your help. I will be sure to take in all of your suggestions when attempting to drill in the future.
M3 is 3mm.
M3 is a screw size

The importance overlooked is class of fit. Usually there is close and standard fit. The screw hole is bigger.
Here's a chart: https://littlemachineshop.com/images/gallery/PDF/TapDrillSizes.pdf

For those of us being really picky, M3 a range of diameters which is nominally 3mm. See: http://mdmetric.com/tech/M-thead 600.htm

I drew so many screws in high school drafting.


Fiberglass dulls tools quickly. Fiberglass is very abrasive to motor brushes. Drill with a vacuum cleaner nozzle nearby if you can.

Holes in sheet anything made with a conventional drill bit tend to turn out triangular.