Does anyone know anything about drawing tolerances?
I am interested in finding out if someone is aware or can
point me to info on "self-tolerancing". I'm not sure if this is the
correct term or not, as I can't find anything under this term on
Google.
If I specify a dimension as 10 mm, without stating a
tolerance, the self tolerance would default to �0.5 mm. For 10.0 mm, the
self tolerance is � 0.05 mm, for 10.00, it would be � 0.005 mm,
etc.
I believe the way it works, is that a number like 10 mm �
0.5 mm can be seen as 9.5 ~ 10.5 mm. When properly rounded upward, any
number between 9.5~10.5 mm would round back to 10.
For 10.00 mm � 0.005 mm, this relates to 9.995~10.005
mm. Again, any rounding of any number inbetween 9.995 and 10.005 would be
10.00.
Thus self tolerances allows for a range of numbers that
would effectively be equal to the desired dimension if rounded. I'm not
sure if this is the actual explanation used to describe this method, but it is
one I understand.
So if anyone is aware of this method and has used it,
please let me know. I tried to explain to a co-worker today that with
metric dimensions if no tolerances are given on a drawing, the number of digits
past the decimal determine the tolerance by implying self-tolerance as
explained. She never heard of it and I couldn't find any referances to
back up my explanation.
Euric
