# How to rig up a projector



## SBWHART (Jul 16, 2010)

The tool room I use to work in many years ago specialized in making form punches that had a series of blending radiuses, to check the forms of these punches we used Batey projectors:- what you did was mount the punch in front of a powerful magnifier with strong light shining through, this went through a series of prisms and an enlarge image of the form was projected onto a screen you could check the form against an enlarged drawing.

OK thats the background.

My problem I want to make a small form tool with a accurate 1mm rad the tool as supplied looks good with the Mk 1 eye ball with a magnifying glass not so good you can see a series of flats, but there is no way of knowing just how close it is to a 1mm rad.

With a Maglite, a magnifying glass some bricks and bits of wood, you can set up your own projector.

Like this







The maglite is at the bottom of the pic on some bricks and chunks of wood, The form tool is fastened to the angle plate with a spring clamp, the magnifying glass is clamped to a Vee block.






This is the screen just a bit of printer paper held onto a steel plate with a magnet.

You have to fiddle about a bit to get the best position for all the bits my screen is about 1 M in front of the magnifyer, you also have to twist things around a bit and move them up a down to get the sharpest image once you've done that just leave everything where they are.

When you got a sharp image with something of a known size just simply measure the image to check the magnification, for my set up I was getting a six times magnification.

My 1mm rad is now a 6mm rad through the projector, so all I had to do is draw a 12mm dia circle on my screen.







Her it is with the lights on.






And the lights off







You can now judge how the rad fits the screen drawing and make fine adjustment as required.

I've know got the image of hundreds of Guys around the world, disappearing into darkend workshops and their wifes wondering what the hell they are up to.

    

Stew


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## Kermit (Jul 16, 2010)

I use one at work almost daily. They are called optical comparators. 

The going rate for used ones is in the multiple thousands and for new ones, tens of thousands of dollars.
Even small ones are ridiculously expensive. It's nice to know creating one for shop use can be done so simply...
AND cheaply. 

Great post,
Kermit


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