Jo,  The +.005 is the amount the board manufacture drills the hole before 
plating. The +/-.003 is the FHS Tol.


                                                               Honeywell
John E. Shaub                   Industrial Automation & Control
Senior Designer                    Honeywell Inc.
Hardware Engineering       1100 Virginia Drive
(DAC) East                              Ft. Washington, Pa. 19034-3260
                                                    Tel: (215)641-4338
                                                    Fax: (215)641-4100
[log in to unmask]





> From:          [log in to unmask]
>
>      Example:  Assume finished plated through hole size of 0.034+/-0.003";
>                minimum annular ring requirement of 0.002"; and, FA = 0.014"
>
>      Therefore:  P = (0.034 + 0.005) + 0.014 + 2(0.002) = 0.057"
>
>
>      Using the information from the above example, I would answer your
>      questions as follows:
>
>      #1  Maximum finished hole size = 0.034 + 0.003 = 0.037
>
>      #2  Value to add to nominal hole size = 0.005 + 0.014 + 0.004 = 0.023

This thread is of interest to me.  We don't use a standard formula
here but I would like to try to have one.  One of my
responsibilities is to develop a "guideline" (the word "standard"
isn't allowed) on creating component footprints.  Right now I can't
justify the pad sizes we are using.  If I had a formula I could start
using that and feel beter about the numbers I come up with.

I was doing fine with Mr. Wolf's explanation until he popped in real
numbers.  He started with .034±.003".  Then he states P = (0.034 +
0.005) Where did that .005 come from?  Or was that a typo?

Anyone care to help me?  I know it's early, and it's Friday, but
surely someone has a few brains cells they can show off this morning.

TIA,
Jo

JoAnn L. Amerson
Design Librarian
Red Lion Controls, Inc.
E-mail: [log in to unmask]
Voice: (717) 767-6961 ext 6308

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