Fred the Red Shirt wrote:
Ernest Christley wrote in message m...

Fred the Red Shirt wrote:


If you have to scale something for yourself off a drawing (or within
a cad model) then my advice is to be cautious and plan for a little
hand-fitting to make it right.


I was referring more to crosscheck measurements. You ever measure
something, maybe even two or three time, and just 'see' the measurement
you expect instead of what's actually there? With CAD, you can drop a
couple of extra measuments. Seeing a second measurement wrong is more
difficult. You have to be trying to screw up the third one. I like to
pull any important measurements from three points when I can. If
they're not all in agreement then I stop to figure out what's wrong.


Again, ideally when fabricating you do not measure from the drawing and
apply the scale factor, and that is without regrad to whether you measure
with a ruler on a piece of paper or digitally within a software package.

You should use the dimensions called out on the drawing to calculate that
crosscheck measurement.

If you like, calculate it three ways and then average the answers.

;-)


Or draw it up in CAD using all the dimensions that the designer gave,
then pull a line from the two points in question. You'll get
measurement accuracy down to nano-inches in a few seconds, vs the hours
it'll take to do 3-dimensional trig through rounded curves.

Personally, I'd never drop a ruler on the plans and then attempt to
scale up by a factor of 8 or 16. The thickness of the lines are enough
to throw you way off at those scale factors.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber