It seems probably quite a few have considered the question. Back in the
'good
old days', holes were spec'd as ... 1/4 drill thru..... Nowadays, it is
more likely to be
spec'd as .... .25 thru... with a corresponding part of the drawing labeled
"tolerances"
specifying how much deviation (tolerance) is allowed as to two, three, four
place decimal
numbers. The same tolerance block would perhaps carry the notation "unless
otherwise
specified, tolerances must meet xxxxxx, whether it be mil spec's, or the
company's own spec's.

I once had the occasion to check on "parts out of tolerance". The drill
press operator
showed me in black & white, "drill #30 thru". And of course he had correct
drill, but it was
so badly worn, it was drilling way undersize.... But, according to print,
he was not at fault.

As you well know, the first place any machinist looks on a drawing is the
tolerance block,
or for any other applicable spec's. A lot of drawings even carry notation
of "generally
accepted good machine shop practice".

Good luck!
"Harold & Susan Vordos" wrote in message
...

"Robin S." wrote in message
...

"Harold & Susan Vordos" wrote in message
...

Gak?

Yeah. What's a "standard" tolerance for a hole?

At work, we do DIN, ISO, Canadian, American and automotive OEM standards.
I've never heard of a standard hole tolerance (when not stated).

Regards,

Robin


Gotcha!

That's what I meant, sort of round about. My experience in the missile
industry taught me that one was not free to stab a hole in any part and
call
it good. While holes often had a specific tolerance, there were times
when
they did not. In that case, QC reverted to specific standards, in my case
to MIL specs. My point in posting what I did was that it's a good idea
to
double drill holes *because* one is likely not free to end up with holes,
size be damned. You just told me the same thing, only supplying the
references to which you must work. Do you wonder how many have ever
considered that holes must be held to a specification?

Harold