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Optical punch
raynerd:
Could someone explain what the optics are exactly, reading AndyF's post, I take it they are simply perpex tubes with a slight dome? This is an excellent idea! I`ve just come back from punching some holes and this little tool would have really helped!!
Chris
andyf:
--- Quote from: craynerd on July 20, 2010, 04:02:25 PM ---Could someone explain what the optics are exactly, reading AndyF's post, I take it they are simply perpex tubes with a slight dome? This is an excellent idea! I`ve just come back from punching some holes and this little tool would have really helped!!
Chris
--- End quote ---
That's right, Chris, though cylinders rather than tubes. Have a look here for a bit more detail:
http://www.gadgetbuilder.com/OpticalPunch.html
Andy
John Stevenson:
I have a bought one, bought it ages ago but it wasn't cheap, about £50 at the time.
It only has a single holder for the perspex rod and you swap for the punch. It all lives in it's own little padded jewellery type box
I feel safer with this one as I'm sure with the double holder type I'd smack the wrong bit with the hammer :doh:
One nice thing on mine is the fact it has an 'O' ring let into the base so it stay put on the job, simple but works well.
John S.
Tinkering_Guy:
--- Quote from: Bernd on July 20, 2010, 09:48:19 AM ---Very nice little write up on making that optical punch. :thumbup:
Thanks Tinkering_Guy. Could you did a little write up how you made that cutter for making the optical curve. :bow:
Bernd
--- End quote ---
Well, it's as was said: it's not real critical. However, if you're a perfectionist, you want to decide a) how long your optic is going to be, and b) where the focal point is going to be. It's pretty safe to work with a refractive index of 1.0 for items this small.
Look at the diagram. The focal point is 1.5mm beyond the bottom of the optic, and you want the focal point to be at 1.5". (The narrow 1" section fits into the .375 hole in the base; the base is ~ 1" deep.)
I went through this, only with a lot more math, and set my boring bar to a radius of 1.5". I faced off the end of the cutter-to-be, lined it up with 0 on the X axis of the mill, and 'bored' a half-saddle in the end of the rod. (Which was actually .375 drill rod, not boring bar stock.) Then I milled down to the midpoint of the rod.
The result was a cutter with the right curve, but with zero relief in any direction. (Not a problem, really, for working with acrylic.) Hone it up, put a stop on the cross slide of the lathe so the end of the cutter won't advance beyond the centre of the acrylic, and shave it down until you have a clean dome on the end at your 1.5" mark. (If you advance the cross slide too far, you'll get a pointed dome, which will introduce distortions out the wazoo.)
I actually set the focal point of mine to be the end of the optic, because I want the optic to actually rest on the work piece. If it doesn't touch, you'll have plenty of parallax problems with your crosshair or circle reticle.
Bernd:
Thanks much Tinkering_Guy for taking the time to post that info. Really apprciate it. :beer:
Bernd
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