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Regarding the races to W to parabolizzare:
Remember that you are working with the mirror above, and ran, and also ooze, those that are of variable amplitude during each pass, and are substantially “accordion”, reaching a maximum of 4/5 D and also a minimum of a few cm.In fact, the amplitude varies vertically and horizontally, as shown in figures A1, A2 and A3 of the image below.
The rides are regular A1 parabolizzazione type.
Next, must work at least one hour, and then put the mirror in support of tests that are done only after 8 hours.
The test environment must have a constant temperature, cold or hot is.
Next, take the test (Foucault or Ronchi). … But you must have previously had a good experience with the test you want to use., in order to be able to identify with certainty the anomalies to be correctedBased on the tests, decide if your edge is too high, then, uses fixes to A3 races;
(for whose accordion shape, see in the figure, They are very close together in the center, and wide towards the edges).And, but nevertheless, we had to delve into the center, then, It will be applied to A2 races (for whose accordion shape, see in the figure, vice versa they are close to the edges and wide in the center).
At the bottom of the figure there are three defect figures, each with indication that it was developed to be used to eliminate.
I with my F5 mirrors I only used the methods of this, with the exception of small diameter tools, making up for this with the use of the over-pressure indicated in figures C1 and C2, to correct within some narrow or over-excavated circular rings.
Stop….
In the sense that the mirror is completed you do not need to act in this way, understand from what test is the defect on the mirror surface, and choose the appropriate remediation action.The duration of the chosen action depends on everyone's way of working, and should be experimented with for a short time and then doing a test to get an idea of how much has changed, Whether little or too much, so as not to exaggerate and fall into an opposite error.
hello Maurizio. I know that in some cases linseed oil or turpentine or beeswax is added. But since I've never done it, I can't advise you,
But I believe that Mirco or Massimo or Enrico could do it with authority.
If you read the articles in this same Blogger, on hardness, pitch melting and casting find information.
However, the quantities to be added are minimal.Thanks for your trust Giulio, unfortunately I have never used gugolz and therefore I cannot quantify the effect “softener” some linseed oil on it.
Our doctor is needed here. ing. Mirco and his experiments on the hardness of materials.
Ha ha ha, thank you for your trust on my part too, but like Massimo, I have never used Gogolz pitch and I would not be able to quantify the effect of the additions well…I have always done all the experiments with calophony, there was bee oil and linseed oil…I'm sorry…
I think Maurizio that you will have to be the one to experiment, and then share the valuable information and your assessments with us…
However, keep in mind that if you decide to add turpentine, the quantity to be added is in the order of one or two teaspoons at a time, while for linseed oil a 1-1,5 % at a time I would say…
Putting myself in your shoes, and having no experience with directly changing the hardness of pitch, I would suggest the shortest way for the direct use of yours #64 as it is, first avoiding unexpected events to soften it.
The Gugolz quality data table says that mine #55 (which I used between 18 and 20° C ambient temperature), it softens at a temperature of 63-64°c; while #64 it softens at 65-68°.
The difference therefore is between the 2 and the 5th.. which are not many.
The first thing I would experience (perhaps the easiest), is to increase those 5 degrees the ambient temperature of the room where you work, or to choose a small place where you will go to work on a trial basis, capable of being heated thus, with a ventilating electric heater.
The test of a pitch (after the necessary good adaptation to the shape of the mirror, carried out if necessary, even with a lukewarm Maria bath) it must last at least an hour without major interruptions. Because under one hour of work, friction never reaches the surface softening temperature of the pitch that is needed for efficient processing.
Softening temperature referred to the surface of the pitch squares, which obviously you shouldn't think you can feel like heat on your hands while you work (the tool certainly does not heat up 50 degrees), but you will certainly hear “with his nose”, given that pitch at that temperature, it spreads the scent of pine needles that you smell when you walk in the mountain woods.
That softening is due to instantaneous seizure/friction heating at the molecular level, immediately dispersed in the mass of glass and pitch.
In fact, the instant seizure of the pitch presents itself to you with a whistle, which is the tangible sign of a series of those events repeated a few hundred times a second, how many frequencies are that sound.And it is precisely that heating that is so concentrated in a very small point of glass contact – care, with the abrasive trapped inside the latter, which even makes glass plastic, “tappando” progressively the craters created by the rolling abrasive of pitch-free grinding.
It seems like a lie, but you realize it by looking at the shape of the craters under a 100x microscope.
The craters of the last grinding grain (for example the 800 or vice versa 1000), they have a chipped and angular perimeter. While your polishing process with the pitch that traps the abrasive, manages to make them with rounded edges, gradually until you fill them with glass and make them disappear completely.Before heating the place where I work (35mq) and take him to 22-23 degrees,and in light of a little experience on the PECE I would like to try again with the Greek pitch improving its hardness,bad that goes with Gugolz I can always remedy…
It could go what you say?I say that you are holding a branded rosin, of which the softening temperature is known, which gives you a precise idea of the optimal or almost ideal working environment temperature.
And this is a safe starting point …as opposed to rosin, of which you wouldn't even have this.Moreover, I'm sure you could find a small room like a bathroom to be heated to that indicated temperature.
So I tell you that your choice for the highest difficulty, It's definitely your right, but it is not rational, in light of your difficulties.
My question at this point would become: But you want to make a mirror with the best chance of success, or experiment on pitch?
I don't want to have experiments on the pitch. The problem e’ only to warm up such a great environment.
But you gave me the idea of the bathroom I hadn't thought about it,And if the stem where work manages to enter it can be done.Well.
You can try postponing any complications until you are comfortable with the new temperature.Ciao, I managed to place a stool in a bathroom with bricks to work on 21/22 degrees.
As I said, I have to go back to the sphere; The central hole is not there now’ more but I am finding difficulty for the sphere and I find myself in this situation you say? Work 1/3 COChttp://s23.postimg.cc/d1xpivlu3/IMG_20160225_185637.jpg
http://s9.postimg.cc/icpt5vbfj/IMG_20160225_185759.jpg
http://s30.postimg.cc/aykch1z4h/IMG_20160225_190020.jpghello Maurizio, yes, the hole in the center has absolutely disappeared and from the photos the surface seems nice and smooth and free of roughness but you have created a great clinched edge (if the images are intrafocal), otherwise raised edge if they are extra.
If they are in intra and therefore clinched edge, I recommend you read the beautiful article written by Massimo:The article indicates what are the main causes of the formation of the clinched edge and the description of one of the methods to correct it.
If instead you intend to continue processing with the full diameter, you have to reduce the width of the pass (kind 1/4 Another detail of the secondary spider) so as to dig the center more. Once the center has also been dug you must regularize everything with further runs 1/3 COC…But first you need to understand why you tend to break down the edge with your runs 1/3, otherwise you risk repeating the mistake later on…
I agree with Mirco, the surface is nice and smooth ! Furthermore, in the second photo there is an excellent setup of the tester !
Well done Maurizio, Ronchi is now “textbook” !In my opinion the clinched edge ( be intrafocal ) It's not that worrying, rather, if you look carefully at the lines close to the edge, you can see that they tend to widen, that is, reversing the trend that they maintained up to a few mm earlier. I believe it is the peripheral sector that has not yet connected with the center, which has been worked on ( good ) to eliminate the hole, while the peripheral part remained with a smaller curvature precisely because they have not yet been reached by the “excavation”.
In my opinion still working with pass to 1/3 or even ad 1/4 as Mirco said ( if we are in intrafocal ) you should reach the sphere in no time.
hello Maurizio.
I also think you are doing a good job, and I also congratulate you on the good quality of the images of the Ronchi test.
If those images are taken in an intrafocal position, I agree with both Mirco and Massimo, because in fact the appearance of a folded edge could actually show the existence of an area that is currently lower than your current center. Therefore not the source of an error but only because it is currently not yet reached by your correction process.I believe that the vigilance you need to implement on your work is therefore the suggested one of shortening the strokes a little by slightly decreasing the forward-backward edge to properly attack the upper center of your mirror, but equally at the same time you should keep an eye out to overflow as little as possible in the right-left direction, because if that lateral edge exceeded approximately a centimeter or two, it may already lead you to work undesirably on the edge, equivalent to too long forward/backward runs.
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