Hi Justin

On Fri, 10 Nov 2006, justinasia wrote:
> 1) On a lathe, I need to know an angle for the taper. It boils down to
> this:
> Length = 2cm
> Taper = .5mm (and some others too).
>
> So what is the formula? It seems to be a right angled triangle, with
> one length 20mm and one length .5mm, so what does that make the small
> angle? (Also the actual formula would be useful as I need it for other
> tapers too.)

If the angle is A, it sounds like the calculation you want is

tan A = 0.5 / 20
A = arctan(0.025)
A = 1.43 degrees (3 sig figs)

If A is small then tan A is an approximation of A measured
in radians. In this case

0.5/20 radians = (180/PI) * 0.5/20 degrees
= 1.43 degrees (3 sig figs)


> 2) I have to measure the internal dimentions of a tube with an
> iregular surface. So, I want to know the crossectional areas. At
> regular intervals down the length of the tube, I will take a number of

Could you do something physical? Maybe you could take a water
holding mould of sections of the tube (plasticine lined with
cling film?). Add water to the mould to around the level of the
cross-section of the mould you want to measure. Add a known
volume of water to raise the level a little. Then you have the
volume of the pipe between the two levels, and can calculate
the average cross-sectional area between those two levels

avg_cross_sect_area = volume_added / (final_level - initial_level)

Adrian.
--
Adrian Rossiter
adrian@...
Home: http://antiprism.com/adrian