RE: Re: Scratch-built CNC mill

An interesting story about a bridge in San Diego, California, was that the bridge was made in Washington; floated in sections on barges to San Diego, and raised into place. The center section was several inches too long and would not drop in because of the temperature difference Washington vrs Sourthern California. The story goes that they flooded it with sea water for a few days to cool it down, so it they could drop it into place.


-----Original Message-----
From: Ian W. Wright [SMTP:ian@...]
Sent: Thursday, August 26, 1999 11:53 AM
To: CAD_CAM_EDM_DRO@onelist.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Scratch-built CNC mill

From: "Ian W. Wright" <ian@...>

CG wrote:

> Why don't we just use glass scales??

The question really should be - why *do* people use glass scales. Close
contacts with a company which made precision measuring products taught
me that the material which machine scales are made from should match
either that of the machine itself or the material being processed. In
this way, its not necessary to take any account of changes in
temperature. That is - a steel scale on a steel machine will remain
proportional at all temperatures. If you are working hard on a large
metal part it gets hot and will consequently expand, so, logically, if
you are relying on a scale which does not expand as much or is in a
position where it is not affected by the heat of the work, the work will
finish up undersize when it cools down. opinions anyone??

Best wishes

Ian

--

Ian W. Wright LBHI
Sheffield Branch Chairman of the British Horological Institute.
Bandmaster and Euphonium player of the Hathersage Brass Band. UK.
See our homepage at:- http://www.iw63.freeserve.co.uk or
http://www.iw63.demon.co.uk/ or
http://www.GeoCities.com/Hollywood/6067/index.html

'Music is the filling of regular time intervals with harmonious
oscillations.'



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