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hello for me it seems really difficult to find the glass discs also calciosodio
you should easily find in the Lombardy region is nowhere to be found, I asked 5
large glassworks but do not exceed the thickness 5mm.
at this point it seems cheaper and less frustrating to buy one newton mirror
commercial and from there.
what do you think?
hello Maurizio.
I think we just have not been lucky in finding the right glassware.
Try to find those defined indusrtiali glassworks.
In practice you have to look glassworks that make furniture for stands or bathroom if you want to find the thickness 20.Do you dare to look in because the windows of torque 310 x 20 'I found her to Asti which is a small city.
Do you want that you can not find it in Milan , doove everything “I know a little pu”
and they say “me too’ Gias e n Pu know little fregg” 
What Lombard area six?As Julius says we need a fitted glass, the problem of the glass is unable to find the sheets 19 mm, but to cut them. Until 5-6 mm cut it “by hand”, then it takes machines. Where servant to me I use the waterjet, If you can not find who makes the discs in your area please be aware that I could have them cut my glassmaker and spedirteli ( not now because the glazier is on holiday ), it sure is a lot cheaper than a commercial mirror newton
Massimo when I did cut my memory that did not use waterjet, but I have marked a little at a time and have broken the gradually forming a polygon with many sides (you should have seen what kind of shrapnel were coming out from the edge) and then have it put on a machine that has ground the entire circumference…
intricate, but it worked…
ok I try in industrial glassworks,I'm in Milan south.
thanks to Massimo proposal I keep it for good if I do not solve.
I asked various optical who engage in various capacities in the construction
of goals and I'll know the results,there would Reginato but the diameters up to 300mm
I am currently not as disponibili.così 200 or 250-
the second asked me a 400mm x 40mm thick Pyrex € 1100
euro 400 sodium calcium.
disco da 330 calciosodio in thickness 30mm € 330
it would be my intention to make a kirkham by 350mm by 20mm but I'm afraid
thick are few Maurizio, I do not know ( and I not want to know ) who made you those prices, both borosilicate for calcium-sodium, but I think they are completely out of reality…
I know of what I speak because a few months ago I was in contact with Schott for providing Supremax glass plates http://www.schott.com/supremax/english/index.html with thicknesses up to 57 mm !Look, if I remember correctly deabis long ago told us something about some discs 410/30 mm sodium-calcium for sale in 75,00 euro each ! if you back hangout link.
found it ! http://www.ebay.it/itm/110953194517
Now some advice:I've never worked diameters from 400mm x and giving good he can to buy
the blank in question which is the best strategy to follow?best work 2 glasses equal
or use a sub diameter?
thank you I would say that because you still hew and dig on the mirror a spherical cap, arrow whose depth depends on the focal length of the mirror you want to achieve.
Could you do it without leaving the “the old road” using a glass tool also often only 20mm full diameter, seen that the operation of the excavation is done by holding the mirror in his hand and pressing its center strongly against the edge of the tool that is always supported on the table, and therefore does not bend.
But we also feel that others say.I have a “woodworm” ahead, I have already expressed, and that perhaps attuerò when I start the next scratching.
It is used for roughing a flange from the half mirror diameter tubes aqueduct, says Mel Bartel here:
http://www.bbastrodesigns.com/JoyOfMirrorMaking/RoughGrinding.html
A similar tool, however, is no longer needed once finished roughing, and then at that point we have to build a tool to full diameter pears standardize the male and female curve, and then to proceed to the ripening of the surface that will precede the polishing.A Dall Kirkham telescope has the elliptical primary and secondary spherical.
So Elliptic primary (deformation coefficient between zero and -1) It is only slightly deformed with respect to the sphere (the ball has deformation coefficient B = 0), and slightly less in the parable (which has coefficient B = -1).
Then, nose I would say that the finalization of the elliptic curve should be a little less demanding of a parabolizzazione.my view is that a 40 cm can still be handled during the roughing / grinding with full tool diameter, basically we are around 10 Kg with 3 cm thick. If you have the opportunity to have two similar drives I would choose the easiest and safest route, which according to me that the tool remains at full diameter.
Even for polishing I see it still possible to use a full-diameter pitch patina, as he did for his Mirco F5, in order to complete the phase “quickly” without necessarily employ the biblical times of the sub-diameter
Unlike will be for the parabolizzazione ( that parable is not, ma “quasi”… ). If the project will focus values ( I presume ) lower than F4, I think the sub diameter will be required, the processing of the elliptical cone of the primary will not be very different from that for the parabolizzazione, the only difference ( as for the hyperbolic ) is the value of the constant tapered to reach that, in this case, It will be less than K = -1.
hello Maurizio, I also advise you to use a utensil full diameter for roughing. I my 400 I blank with a sub-diameter to 75%, But I did machine. Hand in my opinion better the full diameter…
As you also said Giulio for the tool see if you can find someone who will cut a disc from 19 mm. Do not buy two 30 mm thick, It is a sin to throw away a disc 30 mm (so hard to find now) just to use it as a tool…always polite and comprehensive I thank you for the answers they will treasure
I will keep you informed
ciao
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