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Rings on Mirror's Surface

Mirror Making
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6 replies to this topic

#1 iTesla

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Posted 25 October 2021 - 06:33 PM

Hi all,

 

You helped me with an eight inch ƒ8 mirror recently, thanks again for your help. It should be aluminized soon (60 days).

 

I'm attempting to figure a ten inch ƒ4.5 mirror to see if I can do it on my own. In trying to correct a TDE and ignoring the mirror sticking and releasing, I pushed through. I was thinking a little roughness in exchange for a good edge was acceptable. Perhaps not.

 

Are these rings a result from poor contact or are the facets too small and they are the culprit? Or both? OR something else?

 

What size should the facets be?

 

Rings.jpg

 

Lap.jpg



#2 Pinbout

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Posted 25 October 2021 - 07:59 PM

The facets on the lap need to be off center, both directions


Edited by Pinbout, 25 October 2021 - 07:59 PM.

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#3 iTesla

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Posted 25 October 2021 - 10:03 PM

The facets on the lap need to be off center, both directions

So my crosshair lines intersect close to the center of a facet, but they should meet at the red dot. Originally they did meet off center, but after trimming they shifted towards the center. I failed to recheck.

 

I'll have to remake the lap. Is a 1.5 inch square facet too big?

 

 

 

 

Lap copy.jpg



#4 mark cowan

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Posted 25 October 2021 - 11:57 PM

No the size is not a problem, the symmetry is though.  Also vary up the strokes by small amounts randomly (or as close as you can come) because the rings are the result of the same facets (and their symmetrical partners) hitting the same spots on the mirror, along with the channels, leading to over/under polishing resulting in the rings.

 

If you facet like this:

 

9 inch polisher.jpg

 

the problem will not appear as there is very little possible symmetry no matter how the strokes go...

 

 


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#5 Pinbout

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Posted 26 October 2021 - 09:10 AM

So my crosshair lines intersect close to the center of a facet, but they should meet at the red dot. Originally they did meet off center, but after trimming they shifted towards the center. I failed to recheck.

 

I'll have to remake the lap. Is a 1.5 inch square facet too big?

 

 

 

 

attachicon.gifLap copy.jpg

uhmmm.... I put your pic into illustrator, drew a circle around your lap and the green do is the center of the circle.... how did you locate your red dot?

 

you need to be more off center than actually being right on center... ha ha ha

 

ctr right on the money.JPG



#6 Pinbout

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Posted 26 October 2021 - 09:16 AM

but alos press netting into your lap... I use the stuff the supermarkets pack fruit in.

 

https://www.youtube....1Mi3FfQo0&t=23s

 

 

also you can do figure 8 strokes to get rid of all the rings

 

https://www.youtube....jPcDoB&index=12

 

also about the channels

https://www.youtube....h?v=T03b-5LyWGk


Edited by Pinbout, 26 October 2021 - 09:18 AM.


#7 iTesla

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Posted 26 October 2021 - 12:10 PM

how did you locate your red dot?

That was just an illustration where the center dot should be located on a central facet. If you could slide all the pitch so the red dot was moved to the green dot, the lap would be OK or better.




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