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Scratch Resistance of Borofloat33 vs. Plate Glass?

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#1 msheald

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Posted Yesterday, 09:57 AM

Hello! Just curious. With my plate glass blank, I have to be VERY careful in removing the glass from the tile tool when I get to 15 and 9 micron WAO. With the surface tension, I had to slide the mirror about 1/2 to 2/3 to the side to break contact with constant upward pressure on the edges. A couple of times, I let the blank rebound back to the tool and it hit the tile (softly, I think), but I ended up with light scratches that took additional time to grind out.

 

    Is Borofloat33 more scratch resistant than plate glass? The product info says strength is 2x more than plate glass; however, I'm not sure if this translates to scratch resistance. Best regards.

 

Mike



#2 dogbiscuit

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Posted Yesterday, 10:36 AM

Don't try to break the suction. Don't lever the edge of one disk on the face of the other to separate.

 

Slide apart smoothly.

 

Hands at 9 and 3 o'clock, fingers draped over and around the top disk.

Slide one side of  top disk back by moving only left hand back to about 7 o'clock position and wrap fingers around edge.

Now slide the top disk by moving the right hand back while pivoting the top disk around the left index finger, one graceful motion transitioning from sliding off the bottom disk to being held in a good grip with both hands.  Hands, particularly the right hand holds the weight of the mirror from levering up or down during the rotation. On the left side vertical motion is prevented by the pivoting around the left index finger that is in firm contact with both disks.

 

Harder to describe than to do.  Doesn't take much practice to be very smooth at it.

 

Don't know about relative scratch resistance, but if you get something harder than the glass and bigger than the grit you are currently using it is likely to scratch whatever glass you are working.



#3 mark cowan

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Posted Yesterday, 01:39 PM

Yes, borosilicate resists scratching more than plate.  Quartz is even better.


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#4 Mark Harry

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Posted Today, 06:51 AM

Breaking suction in contact interference testing is the method to use for that- and it also correlates well with grinding without scratching. If you learn how to contact testplates with optics, you'll have both situations pretty much in control for avoiding scratches.
(this is opposite #2---I couldn't follow it.--??)


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#5 dogbiscuit

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Posted Today, 10:54 AM

Breaking suction in contact interference testing is the method to use for that- and it also correlates well with grinding without scratching. If you learn how to contact testplates with optics, you'll have both situations pretty much in control for avoiding scratches.
(this is opposite #2---I couldn't follow it.--??)

You are right.  #2 was a lousy description.  lol.gif  Harder to say than to do.

 

I'll try an illustration.

DiskSlideApart-a.png

 

Slide top disk back to position 1 where hands can grip around edge of top disk. Left index finger firmly contacts edges of both disks.

Top disk is rotated pivoting on Left index finger sliding top disk in a steady motion through to position 4 where disks are separated.

 




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