On 06/08/2010 14:36, RussellMc wrote:
>>> 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?
>> You need what is called a "clearance" hole, which for M3 is 3.2mm.
>> In practice a 3mm hole will likely work since a 3mm drill bit guided by
>> hand will most always cut slightly larger than 3mm, but you need to
>> consider the tolerance stack up of the holes in all the parts you are
>> screwing together.
> The following is a "very naughty" thing to do and of course real
> people [tm] would never do such things.
> Can be useful when you don't have the right drill though.
Standard "cheap" box of bits has 2.5, 3, 3.5, 4mm etc.
As do most non-specialist shops.
That's why I recommend 3.5mm for M3 unless you are expert and have=20
professional gear in which case you would not ask what size to use.



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