Thread: Optical centrepunch

Originally Posted by Machtool

Even better, a centre punching hammer, with a magnifying glass built in.

http://www.starrett.com/metrology/product-detail/815

Phil.

That famous Starrett hammer costs a fortune. You can buy a good hammer and an excellent magnifying glass for far less money.

But the advantage in using an optical center punch is not jut the magnified view free of parallax error. It is the punch itself being precisely guided orthogonally to the workpiece to be marker (orthogonally means at a right angle). A slightly angled center punch means that the punch mark wanders in the opposite direction of the lean.

Think about it: how do you correct a manual punch mark that came out slightly off the scribed cross lines? You hit the punch mark again with the punch held at an angle, and repeat this until the punch lines up. Thus follows, that if the punch is not held perfectly orthogonal, the mark WILL be off center no matter how accurately the punch was aligned onto the scribed lines. Guiding the punch perfectly orthogonally is IMO by far the greatest help provided by these optical center punch devices - its by far the greatest contribution these tools provide towards more accurately placed punch marks. The cross hair lineup and the magnification are just nice extras, extras that mainly help the elderly and others with failing closeup eyesight.

Hi sacc51,
I managed to get around to making one a while back and use it way more than I thought I would.
It could be worth a read, but then, probably not
https://www.woodworkforums.com/f65/optical-centre-punch-simonl-155247

Phil

[QUOTE=cba_melbourne;1856981 (orthogonally means at a right angle)[/QUOTE]

thanks for that cba

Yep, I read your thread on these thingies. I've been meaning to make one for a while, only just now got around to it. Whilst in HK I came across a shop that sold nothing but acrylic rods, tubes, sheets, etc, so I bought a few rods and tubes, thinking next of using some of the tube for an oiler for the lathes change gears.

I want to try an LED light in the base so next time I'm near Jaycar I'll get a few different coloured LEDs and try that out.