Re: [Phys-l] Sig figs

[Michael Edmiston <edmiston@bluffton.edu>]

I don't know where your machinists came from, but here is what my experience 
is, and I have worked with many machinists at many different places,

If you ask for 1.011" you will get 1.011".

If you ask for 1.0" you will get 1.000".

Same price.

Any competent machinist will do this automatically.  It was a piece of cake 
for them even before optical encoders.  Even if you only have ruled collars 
on your feed screws (that is, no optical readout of the position of the 
milling machine table or the lathe cutter) any machinist would automatically 
use techniques to eliminate errors from backlash, etc.  Also, they wouldn't 
use lesser machinery to make the lower tolerance piece because they wouldn't 
have any "lesser machinery."


Michael D. Edmiston, Ph.D.
Professor of Chemistry and Physics
Chair, Division of Natural and Applied Sciences
Bluffton University
1 University Drive
Bluffton, OH 45817

419.358.3270 (office)
edmiston@bluffton.edu


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From: "Jack Uretsky" <jlu@hep.anl.gov>
Sent: Thursday, October 14, 2010 12:40 PM
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Subject: Re: [Phys-l] Sig figs

> Hi all-
>  I don't know about chemistry, but I learned as an engineer that
> the difference between telling a machinist that the dimension you want
> is 1.011", as opposed to 1.0", may be a big part of your annual budget.
>  Regards
>  Jack
> "Trust me.  I have a lot of experience at this."
>  General Custer's unremembered message to his men,
>  just before leading them into the Little Big Horn Valley