Re: DIY probing

Hi Ian,

Slide projector? "uses lenses"? Sounds like collimated light. Fits in,
you don't want the light waves diverging. I didn't realize the
"shadowgraph" was a commercial product to document/dimension parts as
small as watch parts.

Back on the probe, why do they use emeralds (or some other synthetic
jewel) for the contacts? I can see it for watch type movements, but
just to "lightly touch" a surface?

Gotta go with the probe, more fun!

Alan KM6VV


Ian Wright wrote:

>
> Hi Chris,
>
> The shadow technique isn't 100% but I use a commercial shadowgraph machine
> for my watch making on small parts and it is good enough for that. One of
> the problems I have using it on small round parts is that the light 'hugs'
> the curve and diffuses a bit to give a slightly blurred edge but I can't see
> that being a problem for you. At least if you get the actual curve of the
> horn you will be able to adjust things with check measurements. The good
> things about this method are that its simple, you get a permanent paper
> record which you can re-measure any time, and it doesn't scratch the metal
> by bumping metal probles into it - totally non-contact. My commercial
> shadowgraph doesn't have a point source of light, by the way, it uses lenses
> to try to get even illumination over the whole work surface. That is why I
> suggested a 35mm slide projector (without slides!) as that is about the best
> concentrated light source I have found for big areas.
>
> Ian
> --
> Ian W. Wright
> Sheffield UK
> www.iw63.freeserve.co.uk