Re: [Phys-l] Sig figs

[Jack Uretsky <jlu@hep.anl.gov>]

I meant my numbers to be exemplary, not to be taken literally.  Surely, 
even today, there are precisions which, if demanded, become prohibitively
expensive.
I spent a few weeks as a machinist while waiting to go on active duty in 
WWII, so m7 experiences date back to them and my 1941 course in machine 
drawing.
			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




On Thu, 14 Oct 2010, Michael Edmiston wrote:

> 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
>
>
> --------------------------------------------------
> 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
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