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Hi everyone, My name is Henry and I write from Carpi (MO)
I also have been infected by this “disease”, is from July I'm scratching a glass disc 26 cm in diameter for 2 cm thick following the advice valuable traits from Astrotecnico tutorial (I thank you very much for the immense work done) and by documenting everything that you can find on the net, than what I read on an old encyclopedia.
I have a small problem that I do not know how to solve…
It is already twice that after some made with dried 1000 appear scratches that force me back to 500, I can not tell if everything is due by 1000 contaminated or if I'm wrong at some stage.
Now I miss some dried with the grain 800 and I do not know how to proceed…go directly to pitch and cerium oxide? settling in 1000?
What do you recommend?
I forgot to write that the intent was to get an F5 but given the inexperience I quit too early to dig through the 80. Currently, the radius of the sphere is about 2733 mm that if not mistaken corresponds to F 5,46 (measurements made with the method of the light reflected on a cardboard). Since this is my first experience as a scratcher is fine with me, ammattirò less in parabolizzare…I hope.
Thanks in advance and really compliments for the excellent idea in making this site…was missing!!!!!!Henry Hello and welcome among us, I moved your message in a new thread for ease of reading and the answers with no overlap with others already open discussions.
How beautiful, another colleague Grattavetro !
Enrico, personally when I hear of lines that appear when working with abrasive for me is always thinking about the same thing: chamfer of the edge to be finished !
Try to view the board with an eyepiece, if you see jagged mo’ of “cliff” it is easy that the micro-flakes from detaching during the passage by the abrasive product and that they are the cause of the problem.This generates lines and in some cases real furrows that appear without warning or particular clue that will reveal the cause.
When it comes to lines we should always try to determine with the utmost certainty what the cause, as proceeding with the processing could unknowingly try to solve the problem by means of the repeated application of his own due.
I'll explain: if the cause is in the chamfer not finished properly, insist with the processing to delete rows can get the opposite effect just because the flakes detach thanks to past with abrasives.
It happened to me that the more I tried to delete and I appeared until I have lost quite a bit’ of time in finishing the chamfer, after which they are no longer extras.
There's an excellent article on the subject Deabis:https://www.grattavetro.it/smussare-specchio-ed-utensile/
Eye that contrary to what one would think, more abrasives are fine is more easy that the scales come off.
Of course, the causes may be other, but this is definitely check with scrupulousness ! p.s. about the focal I too was party to make a F4 and found myself in a parabolizzare F3.8
, it also happens in the best families…hello Henry, welcome
In addition to what you advised Massimo, If I were you I'd do it a thorough cleaning of the workplace. In particular, if the lines are always the same size: maybe you have traces of larger grains in the workplace, the sponge you use to clean, etc
ps: I also left too early in the chordal and now I find myself a f6 (and certainly I will not go focal with finer grits….)Henry Hello and welcome on my part
I agree with the suggestions of massimar and Deabis. I add that a common mistake is to not abound with the chamfer when you have not yet in use abrasive grits purposes, ie the type 220.
In other words, when at that point is realized by a chamfer 3mm is much easier than with what is comfortably arrivals at the end of processing, without having to redo with the consequent risk of rupture of the flakes “deaf” (in the sense of “penisole” Remaining glass hanging by a single fragile stalk who decides to break into finer grits, when it will do the most damage).In the case instead that we should redo the chamfer when already are in vogue fine grains, it is better to pass him smoothing it with a whetstone end reducing the roughness left by the coarse cote.
One other thing that comes to mind is the suggestion is to separate the two disks during the dried, always scroll, But raising the last moment, without going to involve in it the chamfer.
And the more “tricks” They are all here
Hi guys,
First of all, thanks for the warm welcome!
therefore, to be honest I understand that you have not given due importance to the bevel edge…
The practice was, fake the dried with the 800, make a puree with the abrasive dough on the edge of the mirror is that the tool, but certainly not until obtaining a chamfer of a millimeter, moreover, the dough that I am using is quite consumed such as to generate a rounded flange, rather than beveled.
Mistakenly I always thought was enough, as with other troubles, 800 including, I never had problems of that type (that is why we have been led to think that even 1000 it was contaminated!)
Well, the first thing I will get me in a new cote beautiful equal to blunt the edge “textbook” then I'm going to go over with a finer dough.
As for the job I've always done the manic cleaning surgical level enough to be taken “for a ride” from my wife, distilled water, always new sponges between one grain and the other, cleaning of the bench with a pressure washer, etc.. From this point of view I would say to be pretty quiet, But since we all know what happened “quiet” I'll try to pay more attention at that juncture, because there is always room to do better…
Unfortunately the “scratching” proceeds a little slow because of work.
I will not be tempted to overdo it in order to finish quickly, I prefer to take some more time to try to do things as they should…
Thank you so much for the advice!hello EnricoR. I agree with your intent to hone down dough again and with fine grained.
The rounded edge of itself would not be a bad, but it is the cote consumed already used on a mirror to fine abrasives, concentrating your strength in the sun in contact with the glass areas, then scratching in an asymmetrical way and with greater strength on smaller surfaces, which tend to create a slightly wavy edge and more predisposed to splinters “deaf” produced by the same cote.
Co everything, do not think you've done something wrong, because each works in his own way and draws teachings.
Please try again with 1000, and then if the problem occurs again, views your excellent cleaning, it is possible that it may have been the culprit.But even then you could just leave her be and insist with 800 to remove the existing rows, from which grain to pass directly to the pitch and cerium oxide.
I say this because I for example I always used as the last grain 800, and so far I have never used the 1000. Of course the price for sure to have worked a few more hours with pitch.
So much so that, in my case, for example, (have info that I read from my “diary / journal of grattavetro), after 800 which leaves its frosted surface, working in the laundry room under a ceiling neon, After about three hours of cerium and past 1/3 c.o.c. I saw his sharp image “mirrored on the mirror periphery ..(The center always puts more time to polish…ma “eye”, it takes longer to make even the craters disappear!)I agree with Giulio, I also prefer not push beyond 800, had tried previously the aluminum oxide in place of 1000, but I was not satisfied, a bit’ Gymnastics for further polishing stage ( from my very personal and unreliable estimates believe a 20% more time ) It is not a high price to pay…
Enrico, do well not be in a hurry ( deabis must be thinking that I said is not credible
) a good work you should live and lived with his times, also because it is almost always only a prelude to the next.A My curiosity: why did you decide for a 260 mm ? you already have a specific project for the structural part with which integrate the optics ?
p.s. at least, and to you only it happens for debridement, in my case my wife takes me for a ride regardless
Hi everyone!
I managed to find a whetstone same as you see in the video deabis and this weekend I'll try to finish properly trim, however I am seriously considering the fact that they go directly to the polishing once completed the pass with 800…we seeThe reason why I chose a diameter of 260mm is one, in such a network I found that sold the two discs (both 20mm thick) at a good price, glass well seasoned calciosodico, according to her she bought them a 15in years ago with’ intention to implement the optical, moreover he had one more D.260mm to 30mm thick sold a few days before my phone call, I arrived late, patience…
My intention was to create a 300mm, but in my part I could not find a glazier able to get me a similar cut, at least at an acceptable price and in line with qello I read on various forums…For the project an idea of the maximum I, but nothing definitive, for now I plop calculated by the cell sizing 9 floating point (Following the tutorial Giulio), and designed with some particular cad.
For the dimensioning I found very useful this guide
I still have many doubts and prefer to deal with the hand like that I proceed with the project in order not to create confusion…(There assilerò properly)
By the time the’ # 1 goal is to complete polishing (that in itself will be a’ titanic)maybe finding myself with a well finished optics…maybeI realize now that it did not appear the link guide, try again:
http://www.astrofilirozzano.it/Documenti/Articoli/Lez.Dobson.pdfHi everyone!….For the project an idea of the maximum I, but nothing definitive, for now I plop calculated by the cell sizing 9 floating point (Following the tutorial Giulio), and designed with some particular cad.
A tutorial which you refer?
hello Henry, the guide that you posted is an excellent guide.
I also used to take me several ideas for my project…
I in my experience I have always used the grain 1000 and I have always enjoyed it, then as already they suggested you also Giulio Massimo and no one forbids you to go through polishing by 800, but since you already have in the house 1000 I sfrutterei (otherwise it is if I let it get especially delivered)…Giulio I was referring to this:
http://www.trekportal.it/coelestis/showthread.php?t=51602&page=9
Maybe it would be nice and useful to bring “here”… for me it was vital (I think for many others) Mirco I must say that you're making me retrace my steps…
Is’ who I am terrified to hear that type noise again “ZZZZZZZZZZZZZ….” jarring and sudden in the middle of the sweet and reassuring “sssssss…ssssss…sssss” caused by the friction between the glazing…..Maybe it would be nice and helpful even bring it back "here" ... for me it was vital (I think for many others)
caspiterina !!! I share and I stress this fully Henry invitation, the fact is that Julius wants “more good” Coelestis in which the Grattavetro, and to… great authors prefer large audiences
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