Tool for roughing, full diameter or less?

[Stefanosky]

I arrived on extra-hard plaster to make the tools that will serve me. I should start with the first tool, one for roughing, but I read around that for this phase almost all use a smaller diameter because “more effective” and subsequently, once it reaches the desired curve, create tools full diameter to be used for all other phases. What do you recommended about? At the moment I have not decided what I will use to make the tool, is pottery, glass mosaic, nuts or other but I was wondering if a smaller diameter really speeds up the work roughing and if contraindications to watch. in conclusion, I'm all ears.

[Giulio TiberinI]

According to one of my careful examination done for some time, the two best cues machining to meditate to dig manually the initial arrow, are these:

In the document mentioned in the first link, Mel Bartel describes the use of tools in metal disc “Ring tools”, and it states that with such tool constituted for example by a flange made of cast iron or steel pipes for aqueduct, of diameter equal to half that of the mirror, for use with the interposition usually carborundum…( and according to me, seeing the image, I find that perhaps the carborundum is put in excessive amount, with high probability of poor performance to self-destruct) is halved the labor time that you would with wet carborundum relative to the tool with the stoneware piastrelline…Here is the first link:

http://bbastrodesigns.com/JoyOfMirrorMaking/RoughGrinding.html

While the method described by the following link, provides for the use of a tool that is always sub-diameter, that on the working surface a diamond disc fixed port for cutting concrete. Cutting that is known to be carried out with high-speed rotating disk of angular portable grinders.
This method, if implemented on glass and dry, is very dangerous for dust “airborne” inalabile, involving the risk of silicosis.

Obviously the diamond asporterebbe the glass with the highest possible efficiency in nature, and the diameter halved retain their intrinsic efficiency cited by Mel Bartel, with the advantage that with the diamond does not need to other abrasive. And knowing the galvanic technology of fixing the previously chromed diamond grains to the metal support, I am convinced that there are no contraindications to using such a disc anchored to a tool of any material USING IT MANUALLY, WET or even DIVING.

I had read and meditated on these two already dated documents, riproponendomi to try “next time”…(but for unavoidable reasons it has not yet arrived).

http://users.xplornet.com/~tedfoster/pengrndr.html
http://www.jeffbaldwin.org/curve.htm
https://www.cloudynights.com/topic/165004-sine-tabledrill-press-curve-generation/

[Stefanosky]

But then apologizes, the second method as it does to operate? (I do not open the link, After I try from home). The discs have the diamond part just on the edge… The first method with the flange I had seen him, but does not inspire me much… With a tool diameter sub how it would change the type of pass for the roughing step?

[Giulio TiberinI]

If you can not get that pdf, send me a message to the office that I will I send.

The diamond disks for cutting bricks have the dressing that is on the edge of the front and back of the disc, disposed on a circular crown 5mm wide and 1mm in relief on the disc plate (I measured time on my diosco diameter 115mm).

The type of cut is described in the text of Mel Bartel link I sent you, where there is the title “ring tools”, and he explains how to use that type of tool applying cyclically 4 or 5 later he ran back centered on the diameter mirror with light and ooze with strong pressure, and then the usual rotation is the tool in hand, that the operator of a step around the table in the reverse direction.

Using this method, however, you lose the chance to true the tool with the right to the convexity of the curve excavation end, and you make a plaster to continue to facilitate uniform sphericity with past 1 / 3D center to center.
I'll remember already now that the high-strength gypsum precaution should be tested in advance to find out at what temperature the salt mass casting phase of desiccation, the roadmaps damage cisrca 30 minutes.

Often it exceeds 100 degrees and therefore should not be cast on the primary that otherwise would break.

I was assisted by beginner's luck, when I used chalk “to bases” GC Fujirock Base Stone, because after its casting him lifted up from above the mirror just past the setting time indicated in 8 minutes, while the total hardening was 30 minutes, but in that long time the temperature of the mass flow increases to the maximum possibly dangerous that I luckily avoided.

[Giulio TiberinI]

I found your email address in the newsroom, and I sent you the pdf.
Ciao – Giulio

[Stefanosky]

I checked the email but it has not arrived yet nothing Giulio
Gypsum've already tried and warm but not in an exaggerated but I only tried a pound (Had I scared to finish 25 kg?)
From what I've read in some articles the trick is just what, ie remove the mold from the blank after the first few minutes so that it is useful sformabile but which has not yet started to generate too much heat. However if departed immediately with a full-diameter tool plaster could easily use any planar surface for the casting. Unlike if I redo tool after generating the curvature. If I decide to use a roughing tool as described in the articles then you, I'll have to do a test to avoid disappointment.
Tomorrow I start to do something… but what!?

[Giulio TiberinI]

Already you have blank 300x25mm ; the idea of ​​the project, perhaps a F6 ; the stock of patience already accumulated for the need; the work table; chalk .

At your current state, on normal roadmap, the next step would be to decide how to make the tool and make it. And later, to start doing “noise”, You'll need to have abrasives.

[Giulio TiberinI]

Ah I forgot: I'm sorry but I sent for my mistake the file you ineteressava (referred to links that blocks you), to a “another Stefano” thinking it was your address… …Instead it was a French Stefano.. . who kindly understood the mistake and even thanked me because he found it interesting

If you send me a message with your address in the newsroom that I keep his promise, and I will send.

[Giulio TiberinI]

Did I then sent the document / pdf diary quoted above my post another, on the realization of a 14″ with roughing made by hand using a tool whose working surface is present on the diamond crown diamond disks for cutting bricks.

It should, however, ensure that such work performed “dry” It is absolutely to be avoided so as not to inhale glass powder, also because in the initial manual processing roughing of a mirror which is accomplished with the usual simple ran back and forth tool pushed by hand, nothing prevents esegiuirla wet or alternatively you immersion in a basin.

I remember having asked a manufacturer of diamond cut-via online chat, asking if a wet use of them would compromise their reusability safely in a new subsequent use dry; And the answer was that: All dry disks can be used to damp; and that the use of water does not affect in any way the characteristics, indeed better cooling increases efficiency and durability.

[uraniborg]

reading I floated an idea and without thinking much around here,and if one were to use of the disks from the grinding wheel as a tool ?I from Industrial 20, 25cm in diameter of the material are made chui
They should not be very different from ours that we use abrasive,weight and thickness are there with plenty of water may work for the purpose

[Giulio TiberinI]

In principle, those disks would work agrasivi, because they are also made with abrasive grits held together by suitable adhesives.
…I think by this that you are referring to so-called cut-off wheels (that plans) or to disks from which they are said deburring depressed center (that have the hole precisely located in the central depression of the disc).

I think, however, that kind of discs have a much more coarse-grained (low) of the 80 which generally it is optimal for our glass work roughing up to diameters of 400 circa (..over someone starts with 60).

The disc grain is almost never written on them explicitly, but in the form of code.
For example:
The facts discs with abrasive corundum (aluminum sesquioxide) They bring an A followed by the grain that is usually 24…too coarse. While those in carborundum are much rarer and C36 would have the theme song for the most common grain 36…always too coarse.

Too coarse leaves on average because of the craters of comparable size, for the grain 24 is 7 tenths of a mm, against 2 few tenths of grain 80. Which means that to achieve diree excavation arrow 3,12mm (for a 300F6)you have to stop scratching when you find yourself more or less (3.12-0.7mm= ) 2.5mm approximately by the arrow, otherwise many of the cavities left by the grain 24 They would already be deeper than it.

At the limit then it would be better to move towards the experimentation of the diamond disc, which has a very fine grain, diameter 230, It costs less than 20 euro and lasts forever.

[uraniborg]

ok complete answer thank you

[Stefanosky]

I give you quick preview tool I created this morning… I pasted the diamond from 115 mm to a pipe flange to the epoxy glue, after which I made a plaster casting to strengthen the disc avoiding any bending and to increase a little the weight of all. Then I will open discussion specific.

[Giulio TiberinI]

Bello!!
Eye that must not exceed 80 meters per second in the move….

[Stefanosky]

I'll try to control my power Giulio!

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