Fine scratches

[yellowsapphire]

Hi everybody my name is donna, my husband and i have sapphire mines out at the gemfeilds, where we dig our stone, and now for the past 12 months I have been faceting sapphire on a GF5 wich we bought, I have been getting fairly good results, but my question is, on the final polish I sometimes find it difficult to remove the super fine scratches on the sapphire, they are hard to see, you have to keep looking to find the right light to see the scratches, I am using a copper lap with 3000 diamond grit, for the prepolish, and a tin lap using 50,000 diamond grit, for the final polish

 

[silver]

Welcome aboard donna

 

[Mr Magoo]

I have done only about a dozen natural but TBH play around mostly with created sapphire. First cut is done with a 800# sintered. Followed by 8000# on copper prepolish. Polished with 100K on Tin. All on a GF4
I've also tried the gearloose 'Dominatrix' lap which has a 'BATT' prepolish outer band for prepolish and a composite inner band for polish. It works and I have two but would not recommend for a couple of reasons.

I found out recently 'inox' as a lube seems to help reduce 'cat hairs' if you re getting them. Other than that no problems.
I have had contaminant scratching on the Tin lap but have removed that by dragging a craft knife blade across the slow spinning lap.

Do you sell rough at all?

 

[yellowsapphire]

Thanks for the welcome silver, and thanks mr magoo, will try inox as they are only super fine sratches you have to find in the right light, reversing the lap has been helping also, yes we do sell rough stone

 

[SneakyCuttlefish]

Hi yellow sapphire.

In my opinion 50,000# is pretty coarse for a final polish. Try hitting it with 100,000 on a fresh lap dedicated solely to that size. It adds an extra step on top of the 50,000# but it is a good way to test if there is other issues with polishing. If 100,000 doesn't produce the finish you want than I would start looking at your clean down procedure and see if there is possible contamination problems. It is possible that some very fine airborne corundum dust/diamond has become embedded in the tin lap and is causing fine scratches. Happened all the time with with my BATTS but now I store each one in its own ziplock bag and wash my hands thoroughly between grit changes. Also, I remove the splash bowl and polish without it. The rubber bowls most machines use these days are very porous and tend to trap contaminates that can become airborne from the draft of the spinning lap.

Normally 100,000 should only require a quick touch to finish the stone provided the scratches are just faint.

 

[Mr Magoo]

yes we do sell rough stone

Awesome. I'll PM you in the next few days.

 

[Lefty]

Hi Donna, welcome to the forum

My family had claims at Russian gully in the 70's and 80's and I have a couple of pending ones at Reward that unfortunately I have to hand back because they have fallen within the endangered vegetation area - it's been an agonizingly long wait for years through the process, native title etc only to finally be scuttled in the end without ever having put a shovelful of dirt in the trommel. I figure that must have been about all the bad luck I'm due to have in my life though so things should only improve from here

There are often numerous approaches that work. On sapphire, I typically cut the facets in on a very well worn down #600 (probably that worn it cuts with the speed of a #1200), pre-polish with #8000 on copper and then a final polish with #100 000 on a Matrix which is a ceramic lap. On most other things I cut the facets in on a cheapie plated #3000 (they still cut nice and flat) but I find that sapphire tends to orange peel with that approach.

I tend to think that one of the main reasons for fine scratching is caused by a build up of swarf on the lap, tiny sapphire particles that have come off during polishing "ball up" with the diamond and then act as a single larger piece of grit. Give the polish lap a good clean down perhaps?

I also feel that scratching tends to occur less if the diamond is in an oily medium like WD-40 rather than a water-based one but others may have a different opinion.

 

[yellowsapphire]

thanks sneakycuttlefish, great advice, I would say the 100,000 is the way to go, and also thanks lefty for the great advice lefty, my husbands father Alf used to own claims at Russian gully, they actually found a 136 ct golden yellow, wich cut to a 35 ct flawless stone golden yellow, sold to peter brown for $20,000, worth much more these days, they have just sorted out the native title, apperentley you can now peg a claim and it will be completed, thanks everybody, will let you know how we go

 

[Lefty]

That sounds like a helluva find there Donna! Was that Brownie who does the cooking out there who bought the stone?

Our biggest find at Russian gully was a 151 ct blue - but she's a dark midnight blue, just too dark unfortunately. There's a lighter section in it that would facet a really nice stone but we don't want to cut it up. It's got a good shape for carving - do you know anybody out there who carves?

Cheers

 

[fossickeract]

Hi Donna,
I have two suggestions firstly I do an 8000 prepolish using a ceramic lap found the harder lap does a better job with sapphire. The ceramic is different to use but very good once you get the hang of it. If you get hold of one I could provide detailed instructions for successful use. Polish I use 100,000 on a typemetal lap and it works well on sapphire. I have found recently that diamond paste purchased in a syringe has been a bit suspect so have gone back to mixing my own.

Bit of dust but no scratches on this Grabben Gullen party.

 

[Mackka]

That's beautiful mate.
Mackka

 

[yellowsapphire]

Hi Fossickeract,
Nice work, stone looks great. Thanks for the info, I will try 8,000 diamond grit on copper lap and 100,000 grit on tin, hopefully that will fix my problem.