Barry;
I have looked at the specs that I have and could find anything about
"implied" tolerances. I do not have a complete set of specs though.
In my experiences we have always called out a default tolerance. Usually
.XXX = .005, .XX = .1

Tom Garman
PCB Designer
330-575-1636
[log in to unmask]


-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On
Behalf Of Barry Gallegos
Sent: Thursday, June 05, 2003 10:35 AM
To: [log in to unmask]
Subject: [DC] IPC PCB Dimensioning standard

Good morning,
My Name is Barry and I have been asked to locate some information. As I
have
had great
experiences with TechNet, I thought I would Give the Designer Council a
Try.
So here goes.

I ask for some input on the following Message that I received this
morning.

We have an issue on a customer drawing, where the customer calls out
dimensioning on their data, to 3 decimal places, but do not provide a
tolerance table or tolerance indication at all. The exact method the
customer used to call-out dimensions on their drawing is: 250Mils or
530Mils
for example. The pcb shop that built these is saying that, in the
absence of
having a tolerance call-out, they default to IPC standard tolerance. The
customer service person at the pcb shop, cannot tell me which standard
he is
referring to, nor can he tell me what that default IPC standard
tolerance
might be. We do not have the 2221 IPC design standard nor do I know if
it
would cover this issue. We have issue with the dimensions of these pcbs
we
received, including hole positions.

Can you find out what the IPC default tolerance is for dimensioning of
pcbs,
in the absence of having a specific tolerance call-out?

Barry Gallegos
Western Electronics

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