Drawing questions

Apr 03, 2008 2 Replies
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I see these frequently on PCB figures (REF BSC TYP). Could someone kindly explain what these mean? REF = reference (to what)? I pretty sure that BSC is basic spacing between centers? TYP = ?


Also, in datasheet packaging sections, there is often a thin horizontal rectangle subdivided into (usually) 3 or 4 sections. Each rectangle usually starts w/ a symbol (for example, 1/2 circle or theta)in the first section, followed by sections w/ alphas or numberics - oftentimes accompanied by a letter in a circle. Could someone explain this or point me to an explanation as well?



Thanks, Tom


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=_NextPart_000_000D_01C895D2.D7746760 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Blip,

BSC: Basic Dimension. Theoretically exact value shown without = tolerances.

REF: Reference Dimension, usually without tolerance, for information = purposes only.

TYP: "typical" dimension.

The details you seek are all dimensioning standards encompassed in = ANSI Y14.5M, search the internet for it and you will find your answers. = However I am not sure you will find an online source, a quick search I = did only turned up books for sale, no online versions.

The rectangular boxes with symbols and figures is part of the ANSI = standard dimensioning where the figures indicate the type of = measure/tolerance (center point, perpendicular, surface flatness, = parallelism, etc., etc.), the letter usually indicates a datum to which = the measure/tolerance pertains and the numerics are typically the actual = measure and/or tolerance.

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only.

Y14.5M, search the internet for it and you will find your answers. However I am not sure you will find an online source, a quick search I did only turned up books for sale, no online versions.

dimensioning where the figures indicate the type of measure/tolerance (center point, perpendicular, surface flatness, parallelism, etc., etc.), the letter usually indicates a datum to which the measure/tolerance pertains and the numerics are typically the actual measure and/or tolerance.

Thanks for the help...

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