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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Sat May 28, 2016 11:01 am 
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The problem with the Nu-Bonds is they would wear kind of quick, and for a period of time, the quality went down and the new laps were not very good, hence the switch to a 1200 sintered.

I offer no similar products that would replace these, so the following issue has no bearing on this business. Marsh sells something that might, right?

My dealers have told me that product line has joined the Chorus Invisible.

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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Sat May 28, 2016 12:36 pm 
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As using sintered bronze and copper 1200 , just a few times I noticed something not right , as in some larger / deeper scratches ,than normal . A quick redress solved the problem. And I notice no difference really once freshly dressed , Apart from the extra unwanted deeper items , in terms of speed of cutting. Was wondering , could the freshly loosened diamond back up against an ingrained one , being forced higher ? As usually one can tell it is a single item causing the damage , why dosnt it learn its place and be forced down quite quickly ?how can is it persist unless it is tormented by its bigger brothers on a sheet of glass ? That one little diamond? It must be like prison , the hardest one got out .
My sintered laps are only one inch wide so I guess loose diamond dosnt get much chance to cling back on once dislodged very often , fortunately .


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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Sat May 28, 2016 12:54 pm 
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I also find that too much speed is actually slower. The optimal speed on my UT is 600 to 700 rpm. Faster than that It feels like there is less contact/grip with the lap.

As you bring up Nubond, I was just going to start a new topic on that. Was talking with a friend about some old/worn out 1200 Nubond, Dyna discs and a Raytech nubond look-alike 1200.

All are dead, but we wondered if we could skim off the top surface and restore the laps to some function. Actually skim is too cute a word, we're planning on using all of the following: S/D sandpaper, a zirconia sanding belt and/or a s/d drywall sanding screen. Kinda brute force.

Only touched one with the sandpaper which quickly got hot and loaded up with no visible change to the Raytech. What did they use to hold down the diamonds?

This is just a hobby experiment so wasting time is okay. Does anyone have any suggestion as too 'digging' into the surface to expose some diamonds? Kind of like dressing a sintered lap?

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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Sat May 28, 2016 1:00 pm 
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Facetor wrote:
I also find that too much speed is actually slower. The optimal speed on my UT is 600 to 700 rpm. Faster than that It feels like there is less contact/grip with the lap.

As you bring up Nubond, I was just going to start a new topic on that. Was talking with a friend about some old/worn out 1200 Nubond, Dyna discs and a Raytech nubond look-alike 1200.

All are dead, but we wondered if we could skim off the top surface and restore the laps to some function. Actually skim is too cute a word, we're planning on using all of the following: S/D sandpaper, a zirconia sanding belt and/or a s/d drywall sanding screen. Kinda brute force.

Only touched one with the sandpaper which quickly got hot and loaded up with no visible change to the Raytech. What did they use to hold down the diamonds?

This is just a hobby experiment so wasting time is okay. Does anyone have any suggestion as too 'digging' into the surface to expose some diamonds? Kind of like dressing a sintered lap?

I think the the Nu-Bond abrasive surface is really thin. THe second lap I bought from them, the surface started to come off, and it was maybe ¼ of a mm thick or less. Below that was just the base metal of the lap.
I have a 1200 Nu-bond but have only used it for Quartz. Actually leaves a very nice prepolish surface. The 600 Nu-bond to me was the most useful.

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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Sat May 28, 2016 3:28 pm 
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Precision Gem wrote:
I think the the Nu-Bond abrasive surface is really thin. THe second lap I bought from them, the surface started to come off, and it was maybe ¼ of a mm thick or less. Below that was just the base metal of the lap.
I have a 1200 Nu-bond but have only used it for Quartz. Actually leaves a very nice prepolish surface. The 600 Nu-bond to me was the most useful.


The Nu-Bond coating is about 0.10 mm. thick.

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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Sat May 28, 2016 3:37 pm 
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AlBalmer wrote:
Ever try to use a dull machete? It doesn't cut, it crushes.

And a dull razor blade tears. Ouch.

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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Sat May 28, 2016 4:17 pm 
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Also, am I correct in thinking that the sintered lap has bronze holding onto the diamonds and the plated has a harder metal, nickel. Would not the softer metal release more diamonds as Al Balmer worries about? And loose diamonds do generally cause deeper scratches, do they not.


The softer bronze/diamond does indeed release some diamond when dressed, exposing new sharp diamond. Low concentration laps require frequent dressing to make them work. Nickel is harder and bonds well to diamond, but there are serious limitations of how thick the electo- (or electroless phosphide) coating can be in practical manufacturing. In plating, the metal is being deposited literally atom by atom.*
A sintered construction has no such limitations.

*Since the plater is paying by the KiloWatthour, and 'The "international ampere" was an early realization of the ampere, defined as the current that would deposit 0.001118000 grams of silver per second from a silver nitrate solution. Later, more accurate measurements revealed that this current is 0.99985 A.'
So, call it a milligram a second on an 8" lap. How thick do you want it, and when
?

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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Sat May 28, 2016 4:42 pm 
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thomas.adamas wrote:
AlBalmer wrote:
Ever try to use a dull machete? It doesn't cut, it crushes.

And a dull razor blade tears. Ouch.


And well worn and and washed terry cloth towels are good for washing the company car.

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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Sat May 28, 2016 8:05 pm 
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Precision Gem wrote:
I don't think it cuts any slower, and I guess subcounsouly I felt like it cuts faster a bit slower. At high speed it feels like the stone floats on top of the lap.

This is very interesting. I've noticed that for my brand new laps, the same pressure plus higher speed means the stone cuts faster, bit back when I had my plated laps going too fast mad ethe stone feel line it was floating. Hydroplaning?


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 Post subject: Re: Faceting Strontium Titanate
PostPosted: Wed Aug 29, 2018 11:39 am 
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Arya, did you ever get around to testing the subsurface damage theory?

This is one of the most interesting discussions I've found on GemO!

Getting firsthand input from professional cutters is much appreciated, thanks precisiongem!


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