On Wednesday, August 21, 2013 4:25:19 AM UTC-7, Mike B wrote:
This is for a searchlight application where the light source shines backwards

into the reflector which then reflects the light forwards producing a narrow

beam.


So, you make a graph of the shape you want, glue it to a bit of something stiff,
and cut the profile.
Then, mount a block of wood on a faceplate and (cutting on a wood lathe,
or a metal lathe if you are good at cleaning up sawdust) turn it to match
your template.
Put some soft metal onto the faceplate, and spin (pressure-deform the sheet
metal, with a knob-on-stick tool and lubricant) the dish.