Problems with Polishing

[tinker]

Hi all,
      Just a silly question, I have been cabbing for the passed 15 years and oringinally used Silicone Carbide Wheels on my machine, which gave a great final product.   About 3 years ago I changed to diamond wheels and have found that they leave scratches on the final surface, I have used fine grit wheels to try and get the scratches out but to no avail.   I'm thinking of going back to the Silicone Carbide, but before I do can anybody suggest what I could be doing wrong.

[steveo]

Would you not use a diamond wheel for the last one or two passes? Maybe something like a 50000 or 100000 diamond on paper and rubber wheel. Not sure what you call them.

[Rusted]

What grit diamond wheels are you using?
I have an 80 for quick roughing out, there's a good reason why I refer to it as roughing, it's because it is, a very chunky finish with deep deep scratches, rough as guts. It takes forever to remove the scratches using soft wheels.
At present I am without a 220 so all the scratches, chips and chunkiness get removed on the 600 hard, it takes a while. Dry the stone often and check for any scratches, if so repeat and continue.

You could also be getting subsurface damage, the grit from diamond gouges out a channel but also propagates micro cracks out from this channel up to about 6 times the diameter of the grit, when you are trying to finish your stone you are uncovering this subsurface damage which can chip out.
A lot of the scratches that appear on faceted stones done by newbies is subsurface damage from overzealous use of very coarse laps.
If you are having trouble getting your head around it think of a glass cutter, you scratch the surface with the cutter which gives a starting point to be able to break the glass pane right through.

[FlashGP]

I use the following sequence for cabbing.

80,220,280soft or 320hard, 600,1200,3000,polish.

The first step is a litte steep for hard material, but given more space I would use a 120 between the 80 and 220 wheels.

In faceting material, subsurface damage from an 80 wheel can be as deep as 2mm.  For that reason for competition cutting I preform faceting rough on the 220 hard wheel (or skip this step entirely) then rough in using a 1200 lap, cut with 3000 grit then prepolish the meet points into place with 8000 grit and polish with 50,000 or better.

[As I in does tries!]

I use 60 Sintered hard only for de-skining hard agates that I cannot be bothered cutting with a saw, 280 sintered hard for preforming, 600 soft, 1200 soft,
3000 Soft then expando drum for 14000 and 50000 if required.

[MakkyBrown]

I use 60 Sintered hard only for de-skining hard agates that I cannot be bothered cutting with a saw, 280 sintered hard for preforming, 600 soft, 1200 soft,
3000 Soft then expando drum for 14000 and 50000 if required.

Nice I reckon a 60 sintered would be good.
I go my 18xturbo blades wheel, 60 soft, 120soft, 300soft, 600soft, 1200soft, 3000soft, 14k soft

[tinker]

Thanks for the idea's fella's, I use 100grit, 220 360, 600 and then 1200, then onto a cotton pad with tin or Cerium Oxide 3,000.  Its only since Ive been using the Diamond Wheels that I have found the problem, prior to this I was using the Silicone Carbide wheels 100, 220, 400, 600 and 1200 and didn't have the problems.


Thanks again fella's


Tinker

[Aussie Sapphire]

Thanks for the idea's fella's, I use 100grit, 220 360, 600 and then 1200, then onto a cotton pad with tin or Cerium Oxide 3,000.  Its only since Ive been using the Diamond Wheels that I have found the problem, prior to this I was using the Silicone Carbide wheels 100, 220, 400, 600 and 1200 and didn't have the problems.

Tinker

Do you mean you use a #3000 wheel in between #1200 and your final polish with tin or cerium?
Going from #1200 to final polish is quite a jump if I have misunderstood your sequence.

At what stage are you going from hard diamond to soft diamond?  #600?

Cheers
Leah

[tinker]

Soft diamond at 600, then 1200 then 3000 and onto Cerium or Tin oxide. Aussie Sapphire.

[As I in does tries!]

So what wheel is the scratching occuring at?

The scratching does it occur with a single type of stone or all types?

What brand of wheels do you use if known?

Where were the wheels bought?

Just to be clear you are using 100 Hard, 220 Hard, 360 Hard, 600 Soft, 1200 Soft, 3000 Soft, Cerium Oxide or Tin Oxide for polish.