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Equipment Discussions >> ATM, Optics and DIY Forum

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Nelcri
member


Reged: 12/09/11

10" tool blank
      #5647718 - 01/28/13 10:00 AM

Hi, last week i bought a pyrex 10" mirror telescope blank from united lens. Now i am looking for the tool, pyrex is expensive. Then i am looking for some tool with the appropriate thickness (ex. 1.25 inch). Where i can buy this piece of glass to use as tool ?. Thank you.

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wirenut
Pooh-Bah


Reged: 09/21/06

Loc: m'dale Pa
Re: 10" tool blank new [Re: Nelcri]
      #5647893 - 01/28/13 11:35 AM

Have you thought about making one with some ceramic tiles and dental plaster? its most likely your cheapest option.

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KerryR
Carpal Tunnel
*****

Reged: 12/05/07

Loc: SW Michigan
Re: 10" tool blank new [Re: wirenut]
      #5648002 - 01/28/13 12:18 PM

The plaster and tile tools are said to work faster than glass tools, too, owing to the channels between the tiles.

You can use plaster of paris if you seal the tool with epoxy before gluing the tiles on. Hydrostone is waterproof, as is dental plaster mentioned by wirenut above.

Check out the mirror making section on Stellafan's website for instructions on making a tile tool. I'd post a link, but it appears to be down at the moment...


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Nelcri
member


Reged: 12/09/11

Re: 10" tool blank new [Re: KerryR]
      #5648329 - 01/28/13 02:21 PM

Anyone knows the work quality can be obtained with ceramic tiles or dental plaster in comparison with a glass tool ?

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JohnH
Carpal Tunnel
****

Reged: 10/04/05

Loc: Squamish BC Moved!!!!!
Re: 10" tool blank new [Re: Nelcri]
      #5648374 - 01/28/13 02:38 PM

I have now ground three mirror with tile tools, after grinding my first with a glass tool.

I couldn't recall who quickly the tools did it so I am grinding a 10" Pyrex blank with a cast glass tool that has a series of ring channels in it.

It does grind a bit slower but cleaning the tool is much easier as grit gets caught between tiles and tool can lose it epoxy coating leaving pits that hold grit too, thus needing occasional repairs.


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ccaissie
professor emeritus


Reged: 09/13/10

Loc: Whitefield, Maine
Re: 10" tool blank new [Re: Nelcri]
      #5648590 - 01/28/13 04:11 PM Attachment (5 downloads)

I used a plaster tool with pennies epoxied on to produce a 12" f/3. Worked well.

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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: 10" tool blank new [Re: ccaissie]
      #5648648 - 01/28/13 04:35 PM

for 120 to 5micron I use either type of these tools, pennies or glass tiles. for hogging I use a diamond cup tool if I'm starting with a flat blank.



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Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: 10" tool blank new [Re: Pinbout]
      #5648674 - 01/28/13 04:47 PM

Newport sells plate glass tools. I bought one that was already generated to a particular (f/5) curve when I was working on a 14" mirror.

Newport Glass

JimC


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StarDusty
sage


Reged: 10/02/07

Loc: Parsippany, NJ
Re: 10" tool blank new [Re: Mirzam]
      #5649023 - 01/28/13 07:24 PM

If you want a tutorial for making a tile tool or pitch polishing lap a pdf version can be found here:

http://www.clearskyobserver.com/index.php/20-telescopemaking/13-mirror-making...

I have used tile tools on all my mirrors except the 4" Schiefspiengler. For that project the glass tool becomes the secondary mirror.


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Ajohn
sage
*****

Reged: 12/03/07

Re: 10" tool blank new [Re: StarDusty]
      #5650875 - 01/29/13 06:18 PM

I used an old mirror tool and covered it with a layer of plastic padding - automotive filler - and put squares of reasonable quality frost proof floor tiles on it, settled it on the mirror with a bit of pressure and left it to set. It was a pre ground mirror blank. It was ok for medium and fine grinding.

Might be worth trying if you use a diamond cup tool, steel nuts etc to hog it out 1st. My 1st blank was pyrex and I found it wore a plate glass tool away far to quickly to be anything like easy to use.

John
-


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Paul Drufva
super member


Reged: 06/26/11

Loc: Connecticut
Re: 10" tool blank new [Re: Ajohn]
      #5652064 - 01/30/13 11:09 AM

The plaster with tile or pennies, washers,or even nuts cut much faster than a full size plate glass tool. They are cheaper and save a considerable amount of time. Work quality is equal, but requires meticulous cleaning between abrasive grades. I think the plaster/ metal are superior to the tile tools, because as the tiles wear sharp edges are produced which can chip, producing scratches, so greater care is required in handeling them, metal will not do this.

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