> I'm going to be using hex standoffs to stack PCBs on top of each
> other. These hex standoffs use M3 screws which I have found to use
> screws 3 mm in diameter.=20

Up, that is why they are called M3 ... ;))

But M3 also means a certain thread pitch, see web pages like
http://www.metrication.com/engineering/fastener.htm for the details.

> For drilling holes appropriate for these
> screws, I have chosen to use tungsten carbide drill bits. Should I
> select a drill bit exactly 3 mm in diameter (such as this one:
> http://cgi.ebay.ca/Tungsten-Carbide-Multipurpose-Drill-Bit-3mm-
>
/160439853750?cmd=3DViewItem&pt=3DUK_Home_Garden_PowerTools_SM&hash=3Ditem2=
55a
f5e2b6#ht_67
> 3wt_913)
> or should I select something slightly larger? The question is: will
> the screw slide through if I use a drill bit exactly 3 mm in diameter?

Our norm for drilling for an M3 is a 3.2mm hole. This allows sufficient
play to deal with pole positioning tolerance in both the PCB and what it
is being mounted on, for things to 'just screw together'.

Also I will assume you are aware that you can get the spacers with a
threaded stud on one or both ends (seem to be known as male-female or
male-male as appropriate). E.G.
http://onecall.farnell.com/ettinger/05-17-344/spacer-unc4-40x5-m3/dp/146
6788
 These are very useful when doing a PCB stack.
--=20
Scanned by iCritical.

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.