Optical centre punch

[olderdan]

Hi knoba
I found your optical punch design on your website before joining HMT. I copied it right away and it has been my go to marking punch ever since. I have used a HSS punch and all acrylic for the rest and made two optics, one with crosshairs and one with a bullseye (this is my favourite) I even copied the storage tin. Many thanks for the idea and everyone should make one, it never misses the mark.



Well deserved award
Regards
Olderdan

[Christophe Mineau]

Agree with olderdan, but can somone explain how to polish the acrylic lens ?

[olderdan]

Agree with olderdan, but can somone explain how to polish the acrylic lens ?

Acrylic is one of the easiest materials to polish, after removing any machining marks with 1200 grit wet & dry any metal polish (or jewellers rouge if you have any) hand worked will quickly do the job.

[Christophe Mineau]

OK thanks, I think I had bad experience in the past, maybe I was too fast on the polishing disk, will try by hand next time.
Thanks !

[Toolmaker51]

In the trade, these are known as bombsights.
My optical center punch is commercially made, it's a long time 'friend'. I have no clue about the optic radius, actual magnification or focal length, but it must be relatively high.
I'm near-sighted yet cannot use it without eyeglasses, that would make the focal length at least 18". It's not crosshairs but a .003 dot, slightly wider than a fine scribe line. It will locate centers within .002 all day.
There is no reason to suspect knoba's is any less accurate, therefore a worthwhile project.

[Okapi]

OK thanks, I think I had bad experience in the past, maybe I was too fast on the polishing disk, will try by hand next time.
Thanks !

Hi Christophe,
You can found polishing paste for watch synthetic glasses which goes for cleaning and polishing all optical sights or protecting glasses in the workshop, the result is spectacular only with a clean cloth and some human oil… ;-)