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>> No, but it's a typical value with some tolerance. On our drawings we
>> always have stuff that is labelled like 16.68 +/- 0.20 mm, if they made
>> all the parts with an average of 16.66 mm then some of them wouldn't fit
>> together properly.
>
> As I understand it, the stuff you make is somewhat smaller than a
> building. ;-)
Exactly the same principles though.
Imagine you have a rise of 3050mm that you want to meet with 10 steps, and
you can make each step with a tolerance of +/- 50 mm.
You might specify each step as 305 +/ 50 mm, which will give you a total
height of 3050 +/- 50 mm. Using your argument though, you would say the 305
is pointless and you may as well just say 300. That would make every
staircase 5cm out on average!
In buildings I would imagine that lots of distances add up, and if you don't
at least aim to make each one correct, then at some point something is not
going to fit.
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> scott wrote:
>>>> That's because people who build the stairs works with that order
>>>> of tolerance (mm).
>>>
>>> So... what the hell do you do if you build some stairs, and the
>>> sement sinks by 0.4 mm while drying? (A perfectly likely outcome.)
>>> Then each step might be 0.4 mm out...! No noes! o_O
>>
>> Who secures stairs in place by resting them on unset concrete? :-S
>
> I was thinking more that the *stairs* are made of concrete...
Concrete stairs are usually build in a workshop, poured into
a plywood form, upside-down (so the walking surface is at
the bottom of the form, giving a mostly perfect look and
dimensioning to the visible parts).
Fabien.
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Fa3ien wrote:
>> I was thinking more that the *stairs* are made of concrete...
>
> Concrete stairs are usually build in a workshop, poured into
> a plywood form, upside-down (so the walking surface is at
> the bottom of the form, giving a mostly perfect look and
> dimensioning to the visible parts).
Really? I assumed they made them on-site. (And that that was the
principle advantage of making stairs out of such an otherwise
unattractive material when numerious better alternatives exist.)
Oh well, you learn something every day. ;-)
(Did you know, Boron is what makes silly putty so weird?)
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scott wrote:
> You might specify each step as 305 +/ 50 mm, which will give you a total
> height of 3050 +/- 50 mm.
Did you mean 305 +/- 5mm?
--
Darren New / San Diego, CA, USA (PST)
Remember the good old days, when we
used to complain about cryptography
being export-restricted?
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>> You might specify each step as 305 +/ 50 mm, which will give you a total
>> height of 3050 +/- 50 mm.
>
> Did you mean 305 +/- 5mm?
Oops yes, actually no, thinking a little more about it the correct one would
be 305 +/- 15.8. (tolerances like this are normal distributions, not
uniform...)
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