Author Topic: Optical centre punch  (Read 8698 times)

Arbalest

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Optical centre punch
« on: February 17, 2013, 12:03:33 PM »
Anyone have any observations/suggestions/pictures etc before I start making one?  :)

I don't have any suitable brass (which I'd prefer to use) so the base will probably be alloy. I also plan to have just one hole in the centre of the base and store the punch in a hole in the box instead.

Offline John S

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Re: Optical centre punch
« Reply #1 on: February 17, 2013, 12:29:12 PM »
Good idea the one hole.
Knew someone who made the two hole model where the lens / punch sat in the spare hole then missed the punch with the hammer and smashed the lens into dust.

Hasten to add it wasn't me, I have a bought one hole model and usually when I make a cock up if far bigger than that  :P

Don't forget the groove in the bottom to glue an O ring into so it doesn't slide all over.
John Stevenson, Nottingham , England

Arbalest

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Re: Optical centre punch
« Reply #2 on: February 17, 2013, 01:28:07 PM »
Oh yes, the O ring! Thanks John.

Offline Tin Falcon

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Re: Optical centre punch
« Reply #3 on: February 17, 2013, 04:52:05 PM »
i made  one a couple years ago. I tried poly carbonate for the lens. Lucite works much better. my commercial  one has cork on the bottom. the one i made ai used a rubber pad.
Tin

Offline Bearcar1

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Re: Optical centre punch
« Reply #4 on: February 17, 2013, 05:27:37 PM »
This thread has me thinking about something that crossed my mind quite a while ago and that is, has anyone made one of these optical punches that incorporated a small LED in the base to better illuminate the area being scrutinized? I have never used one of these devices so do not know how much ambient light gets down into the bore but just thought that a bit more light might be beneficial. I've read the ups/downs of using different material for the clear locater piece as well. It would seem to me that a glass rod would be best suited for the job but handling glass would cll for extra safety precautions. These are just random ideas but am sure that others have had similar glimmers of questionable knowledge and perhaps they would be willing to share them with us less accomplished souls.  :slap:




BC1
Jim

Offline John S

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Re: Optical centre punch
« Reply #5 on: February 17, 2013, 06:12:08 PM »
The original ones were made by a firm in London called Dankroy and came in a jewel type padded box, well made and well presented.
they used to advertise in ME.

I bought one of these, reckon they were about 42 which was a fair bit of dosh at the time.

Few years ago I fancied getting a couple of spares and managed to track the guy down. he was a bit amazed i had found him as he's been retired a few years. Long , short was there were no spares but he did tell me he had problems producing the lens part to remain consistent and these were actually ground from perspex rod, then polished.

With the advent of CNC that curve would be easy to do. I even had a friendly physicist work out the required radius so it focused at 40mm long. Interestedly enough that distance alters depending on the material and reflection of light, glass was either half or twice [ can't remember ] the value of perspex.
John Stevenson, Nottingham , England

Arbalest

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Re: Optical centre punch
« Reply #6 on: February 17, 2013, 06:18:27 PM »
The ones we have at work have Acrylic (Perspex) rod. How much light hits the target depends on how much of the rod extends above the base I expect. There was an article in Model Engineers Workshop of how to make one.

Offline Mosey

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Re: Optical centre punch
« Reply #7 on: February 17, 2013, 06:21:20 PM »
or, you could order one from MSC for about $75.00 (that's enough) and it will be perfect.

Now made by SPI, and the plastic view piece is $35.00 alone

I have 2 (don't ask) but I paid a lot less ($35.00)  some years ago. It gets me within 1 or 2 thou. easily if my eyes can handle it.

Offline AdeV

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Re: Optical centre punch
« Reply #8 on: February 17, 2013, 09:56:16 PM »
I scored one for free*, it's a two-hole type, cork base, it has a small "o" printed at the bottom of the plastic rod, simply centre that on your X and the job's good. I take the plastic piece right out when I'm bashing the punch, purely to avoid the "oops, missed" scenario.

Ambient light should be enough so long as your workshop's well lit; mine doesn't work so well in some of the darker recesses of the shop.



*free... I had to buy a 300 lathe to get it, but I later sold the lathe without the optical doodah for 300... hence, free.
Cheers,
Ade
--
I'm just a poor old man. I have no time for law-breakers. My legs are grey. My ears are gnarled. My eyes are old and bent.

Offline Buster

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Re: Optical centre punch
« Reply #9 on: February 17, 2013, 10:28:08 PM »
21 in their sale, comes with 90 & 60 degree punches and two perspex lenses, its the two hole version with cork on the base: http://www.tilgear.info/products/5885/103038/ocp380set__optical_centre_punch/ and in a wooden box

Arbalest

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Re: Optical centre punch
« Reply #10 on: February 17, 2013, 11:13:21 PM »
Good find, and at 21 I may have bought one had it not been for nearly 7 postage!
What a rip off, and with "no image available" you don't know what you're going to get.

Offline John S

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Re: Optical centre punch
« Reply #11 on: February 17, 2013, 11:31:36 PM »
Tilgears stuff is usually bottom of the line, Silverline stuff like that
John Stevenson, Nottingham , England

Arbalest

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Re: Optical centre punch
« Reply #12 on: February 18, 2013, 07:20:40 PM »
If it's of interest, Jim found an article on making one in issue number one (summer 1990) of MEW and I've found another in issue 25. Neither of them look like the article I originally read though so maybe it was in another magazine?! Still, I have all the information I need  ;)

Offline Tin Falcon

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Re: Optical centre punch
« Reply #13 on: June 11, 2013, 11:08:07 PM »
Grizzly H5781 Optical Punch Set




Two punches 60 degree and 150 degree and two lenses cross hair and bulls eye.
US $ 36
My marks on and my home made shop made one both work well.
 Not hard to make.
Tin

Offline Mosey

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Re: Optical centre punch
« Reply #14 on: June 12, 2013, 01:01:35 AM »
Tin,
That looks like a gooder.
What is that nice wooden box peeking in the background?
Mine come in  plastic jars, which are OK.
Mosey

Offline Tennessee Whiskey

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Re: Optical centre punch
« Reply #15 on: June 12, 2013, 01:38:14 AM »
I been wanting one of these. Hey Mosey, help an old redneck out and send me one of yours till my momma's back gets straightened out :lolb:

Eric

Offline tel

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Re: Optical centre punch
« Reply #16 on: June 12, 2013, 02:34:02 AM »
Quote
I been wanting one of these.

Woffor? Y'awl can't gut catfish with it. :Lol:
The older I get, the better I was.
Lacerta es reptiles quisnam mos non exsisto accuso nusquam

Offline Pete49

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Re: Optical centre punch
« Reply #17 on: June 12, 2013, 04:52:02 AM »
For those that want to make their own this is the site I used when I made mine. I turned out ok though I made the base from steel for the weight factor. Hope this helps
http://www.gadgetbuilder.com/OpticalPunch.html
Pete
I used to have a friend.....but the rope broke and he ran away :(