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Mmm… it may be that in the first hours of polishing I made the rosin adapt too little with the consequence that the center of the mirror was in more contact than the periphery. For a couple of hours now, however, I have let the tool adapt for longer and in fact I have noticed a better distribution of friction.
Assuming this is the cause, continuing to work with a well-adapted tool should return to its place?
Another suspect could perhaps be too high an ambient temperature? I tried never to work above 26° (for example today it went up to 28.5° and therefore I didn't work) but, although the pitch is given for 26° its optimal range seems to vary from 18 to 26° according to the supplier. What do I do?
Assuming this is the cause, continuing to work with a well-adapted tool should return to its place?
and, without the need to change the type of rides
Another suspect could perhaps be too high an ambient temperature? I tried never to work above 26° (for example today it went up to 28.5° and therefore I didn't work) but, although the pitch is given for 26° its optimal range seems to vary from 18 to 26° according to the supplier. What do I do?
The temperature out of range ( for both upper and lower values ) it does not stop the pitch from working, but limits its effectiveness. In practice, the more you move away from the optimal temperature, the longer it will take to do a certain job.
If anything, the risk is that, if it gets too soft, it will not be able to maintain the correct shape for a long time and therefore we return to the problem of adaptation.Ok, but what is still not clear to me is whether TOT also needs to be worked… so far for polishing I have worked only and exclusively with the mirror above. Working only with the mirror above, however, a complete polishing of the entire surface is obtained? I've read conflicting reviews.
A well-suited and well-crafted patina does not need much maneuvering to properly polish a mirror, above or below is the same.
I agree with Max that “magic word” which always makes a substantial difference in the working relationship between a “grattavetro” and its pitch, is…. “Adaptation”.
In fact, if a soft pitch is very difficult that does not fit readily, and even if he does not, It would not damage the mirror because very reverentially deforming against the mirror ends up “lick” only very little working profitably…Another danger is instead a hard pitch, and therefore reluctant to adapt in a comprehensive manner. And if this is nevertheless still used, ends “to dig” its curvature error over the entire surface of the mirror.
Is’ true that even in this case is a grave matter, because it makes up doing a new adaptation SOME, and it goes back to the sphere, with an obvious increase of work, but he lost heavily only a few nanometers of vetro..il which however is not a drama (…because with great physical fatigue, it would take a thousand errors to correct for missing a micron thick glass).
That's why the adaptation of the pitch is useful to be verified by interposing, before compression, a polyethylene film sheet Domopak between mirror and tool, to visually check the disappearance of the translucent indicating a local adaptation failed, in favor instead of a shiny black polyethylene adhering to the pitch, sign of good adaptation.
I forgot that with regard to the mirror position above the tool or vice versa, always worth the marble canonical rule “ternaria” works :
1) racing 1 / 3D c.o.c, (but also a little more extended only in this case) Working in conjunction with the mirror above the tool, removes glass from 70% the diameter towards the center, deepening, leaving unchanged the outer surface at that 70%.2) Conversely mirror under the tool removes glass from 70% diameter towards the periphery, leaving untouched the central surface until that 70%.
3) It follows that the systematic alternation of the two positions remains “stop” the depth of the arrow (and thus the focal length of the telescope).
It Giulio, but if we talk about polishing only, changing the mirror/tool position I have never found any substantial difference, all areas are still reached by processing.
Moreover, I agree that the mirror above works the center more and vice versa, and a we limit ourselves to 1/3D runs only, however, this machining difference will not change the resulting shape, which will always be a sphere.
The only difference ( Of course I speak from what is my experience ) lies in the fact that with the mirror above a sphere is always generated’ more “closed”, ( at the nanometer level ) while with the mirror underneath the figure will tend to “open” towards a larger radius of curvature but, I repeat, always within the limits of the spherical figure.
So I guess the 70% you were talking about, is a useful simplification that serves to make the concept immediate and easy to understand. I actually think the “gradient” of processing is more continuous, with a maximum in the center ( in the MOT case ) and a minimum tending to zero at the mirror edge, which will never be null anyway.
If this were not the case, a spherical figure could not be generated from this process, the scope ,as already mentioned, it is the only curved geometric figure that allows two surfaces to be kept in constant contact, however, the move over one another.
If the two workpieces limited their action to a single portion of the surface, depressions would soon be created with respect to the other areas ( as in the case of racing at W ) in contradiction with the aforementioned property of the spherical figure for which, the races in question could never generate a ball.
Interesting… Can you tell me an overall draw, from – until +, sufficient to test a good range of mirrors and clearly valid for what I'm working on
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I would like to understand which comparator or micrometer to use on the test bench (although for convenience I would prefer a digital comparator).
I have seen a digital comparator with excursion 24 hmm at a good price, they might be enough +12 e -12 quickly?Just a 50mm Palmer or equivalent comparator -25+25.
The draw last hm ^ 2 / R peripheral zone, is what supplies the data that circles.
(Where hm ^ 2 / R = median height h of the last Couder to the square of the mask window, divided by the radius)
The draw must obviously increases as a function of the decrease of the focal length.
Because the shorter the focal length, and therefore the deeper the “bowl” of these parable, and the greater the draft excursion to measure it.To do so a hypothetical 800F2'd need a stroke of 46.8mm
600F3 serve for a 23.4mm
400F4 serve for a 11.5mm
300f6 serve for a 6mm
300F3 serve for a 12mmIn the design of the tester please keep in mind you need to have a few millimeters more than strictly necessary, because it is a margin which makes it more comfortable positioning of the meter to be sure to hold the necesario draw within the range of excursions available comparator or micrometer is.
I used a micrometer 0-50mm Mitutoyo broke in the digital display, taking away the bow and using the single knob with its micrometric screw and clutch.
On the market stalls happen to find because in ISO certified companies 9000 the tools to be discarded slightest defect, and the defect of those digital (at least in company where I worked), It is that unfortunately are frequently to be scrapped because they fall on the ground and breaks the display, but all the rest of the mechanics remains very healthy.Thanks Massimo. Indeed with races 1 / 3D c.o.c is not given to change the sphere easily, if you do not stretch a little racing.
The Texereau in effect says to stretch them a little. But with others they wrote those rigid rules probably taking into account the insistence of the self-builder amateur astronomer, that as the drop “hole stone”, and in repeating a negative attitude he finds himself in error.
Although this should also be seen in the light of the practical fact, that a certain variation of the arrow which in the construction phase of the optics leads to a variation of the desired focal length, it is never significant (…as long as it is not a “binoscopio”).And this kind of “rigidity” of the rules indicated by the universally known manual glass scratching system, It is also one of the forces and the operational certainty that it provides to those who engages, because they are made to protect the neophyte from falling into an easy mistake.
A similar fact equally very hard put into practice, but which also constitutes a written rule parabolizzazine, It is the correction of the optics with the tool at full diameter, counting on the overpressure to be applied with the palm of the hand of a tool (which it is very rigid by its very nature), passing locally with the W strokes on the annulus to be corrected.
Of course with hard work and difficulties in applying the W running in the right position, You can obtain some results, with the knowledge that today I would be much better with the use of a tool diameter sub, learning to use it as you have explained, and to standardize the surface with a larger.Cabbage, They haven't sent me any emails like that, in addition to those of the order that would have been processed as soon as possible… Panic, I don't want them to send or refund, mostly because I'm without.
Stefano, I'm sorry for these inconveniences, I hope they get resolved, anyhow,in a normal copy shop you can have the grid file made with cad printed on tracing paper for laser printers and converted into an image or pdf at least 300 dpi. ( cost 1 euro )
If they don't have the right card, it is easily found in office stationery stores at a cost of a few cents per sheet.
Once printed, it is cut out and mounted on a slide frame, I assure you it works great, moreover, on an A4 sheet you can print at least twenty grids of different line/mm formats, just prepare the file suitable and customized to your needs.I think it depends a lot on who has processed your order and who should process my. the answer was sent to me by the Vice President of the Company.
They probably have had complaints from some foreign customer who has not received the goods, and they actually can not do zero because the delivery by regular mail costs a little but is not traceable.I thanked answering these things happening today in the world, although I was not yet happened, and I understand their concern.
(In my opinion, given the universal automation that is being shipped, the loss of mail can only happen during delivery or post delivery to two facts:
1) For because of postmen “faithless” knowing that the absence of control, regular mail to throw away on purpose to lighten fraudulently their work.
2) For astute customers who protest the failure to receive a fraudulent according to ask Free delivery….( and Italians know that may well happen).But then, given the opportunity, I took the opportunity to add a Postscript where, only to talk, come ATM “Insider” and editor of the non-commercial site ATM The Grattavetro, given the difficulty obtaining it in Europe for objects of their commercial section “mirror kit and suppliers”, venture the suggestion to find a European distributor.
I think you'll see that you'll get the crosshairs.
Well Julius, let's hope so… However I thought they needed very precise laser printers, not the office classics. I have as many of those as I want. I will try to make a test sheet while waiting for them to arrive.
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