# Optical Centre Punch



## th62

I made this optical centre punch a while back, thought someone might bve interested. 

The base is a piece of 40mm S/S.   I bored the base 11mm for the lens, cut grooves on the side to accomodate O rings for a secure grip, dished the bottom to around 12mm then drilled a 5mm hole horizontally from the side into the dish to accomodate a 5mm LED.   The whole thing was then mirror polished including the bore and the dish.   The polished bore ensures a nice sliding fit for the lens keeping scratching to a minimum, the dish for better light refraction.

The lens I made from a piece of 12 mm acrylic rod which was turned down to 11 mm on the lower section, Then top and bottom of the rod were polished.   I then scribed couple of rings at the top and cross hairs at the bottom.   

The light consists of a switched AA battery box with a 5mm LED soldered to the end of the flying leads.  

I also made two other light sources:  

The first is powered by a 240/12v power supply.   The positive lead was interrupted and a 470 ohm resistor soldered in place, heat shrink applied to the join and the plug at the end cut off and an LED soldered in it's place with a short piece of physio rubber shrunk over the top.

The second source is a small USB cable with the micro plug removed and a 5mm LED with 100 ohm resistor soldered in it's place and again a short piece of physio rubber applied over the top.   This one can be powered by phone charger, tablet, power bank or any other 5 volt source.

Excellent for centre punching accurately, easy to make and a good toy to play with.


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## Ulma Doctor

very nice work!


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## EmilioG

Nice.  I have a Skidmore but wish it had a non skid pad for punching non ferrous metals. The magnet works
well though for steel.  I'd buy one if it could be used with brass w/o slipping.  Nice work.


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## thomas s

Nice work thanks for posting.


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