Re: Positional tolerance question


"Anthony" <tonytn36sp@xxxxxxxxxxx> wrote in message
news:Xns96A6C3DEC8F93acziparle3sp835@xxxxxxxxxxxxxx
...
> Kirk Gordon <kg1@xxxxxxxxxxxxxxx> wrote in
>
news:1123002811.31714f291a4bd812334bb2108bdeba61@te
ranews:
>
>
> > On the other hand, I've never heard of a
tolerance that was
> > proportional to the size of the workpiece,
except in special cases
> > like flatness, for which tolerances are often
expressed in thousandths
> > per inch. Some casting and forming operations
also have standard
> > tolerances based on the size, cross-section
area, etc., of the
> > material. But for machined features, and
especially for something as
> > simple and straightforward as a hole location,
I think the very idea
> > of proportionality is far-fetched, and likely
to cause a boatload of
> > trouble.
>
> Actually Kirk, our QC standards do call for
proportional tolerancing for
> non-explicitly toleranced dimensions per ISO
2768. BUT, this is clearly
> defined on EVERY print.
>
> ISO 2768:
> Length: (MM)
> From To Tolerance
> 0.5 6 +/- 0.1
> 6 30 +/- 0.2
> 30 120 +/- 0.3
> 120 400 +/- 0.5
> 400 1000 +/- 0.8
> 1000 2000 +/- 1.2
>
> Angle: (°)
> From To Tolerance
> 0 10 +/- 1°
> 10 50 +/- 30'
> 50 120 +/- 20'
> 120 400 +/- 10'
>
> Radius/Chamfer
> From To Tolerance
> 0.5 3 +/- 0.2
> 3 6 +/- 0.5
> 6 30 +/- 1
> 30 120 +/- 2
> 120 400 +/- 4
>

I have seen things like that too. Especially with
hole sizes. Over an inch had a bigger tolerance.
and then sometimes they throw in that M with a
circle around it.


.

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