Faceting Topaz - Trouble on 3K Lap

[Tien]

Anyone facet topaz and have had to spend an inordinate amount of time on the 3K lap? I use Marsh Howard's Lightning Laps, which are great by the way. However, i am working a piece of topaz now that is taking many hours for the 3K lap to work out the surface left by the 1200 lap. I have oriented the stone off of the cleavage plane and am experiencing this problem on every facet.

The only thing I can guess is that maybe my 1200 is contaminated and is leaving deeper than usual scratches. That or maybe the topaz has irregular crystal growth causing me problems. I can see that the 3K lap is working out the scratches but at a painfully slow rate...an hour for the bigger facets. An hour is far far too long to spend on a facet on a single lap! I've had no issue with quartz and beryl. Anyone else have a similar experience?

[gemfeller]

Hi,

Never had problems with topaz that's not oriented to a cleavage plane. Do you have an 8K lap? Sometimes 3K gives problems with certain stones and a jump to a finer grit helps now and then. Don't know why exactly but it can sometimes help. Let us know the results if you try it.

[Tien]

Thanks! I do not have an 8K lap but may get one soon.

[gemfeller]

Feb 13, 2017 19:52:21 GMT -5 Tien said:

Thanks! I do not have an 8K lap but may get one soon.

Hope it helps. Welcome aboard, by the way. Hope you like what you see here. Not many factors so far but maybe that's changing.

[QuailRiver]

Feb 13, 2017 19:11:19 GMT -5 Tien said:

Anyone facet topaz and have had to spend an inordinate amount of time on the 3K lap? I use Marsh Howard's Lightning Laps, which are great by the way. However, i am working a piece of topaz now that is taking many hours for the 3K lap to work out the surface left by the 1200 lap. I have oriented the stone off of the cleavage plane and am experiencing this problem on every facet.

The only thing I can guess is that maybe my 1200 is contaminated and is leaving deeper than usual scratches. That or maybe the topaz has irregular crystal growth causing me problems. I can see that the 3K lap is working out the scratches but at a painfully slow rate...an hour for the bigger facets. An hour is far far too long to spend on a facet on a single lap! I've had no issue with quartz and beryl. Anyone else have a similar experience?

What type of laps are you using - plated?...copper?...tin?...composite?

Larry C.

[micellular]

The last topaz I did took forever to polish with 100k diamond from 3k charged, but the 3k step from 600 sintered took just a little bit longer (like 1.5-2x?) than hard-but-easy stones like beryl, using the same lap setup.

[Tien]

Unfortunately I gave up on the stone. I have a friend who facets as well and he offered to take a shot at it and see if he has the same problem. Both my 1200 and 3k laps are resin bonded. I know topaz is an 8, harder than quartz, but it is taking far too long to work each facet on 3k. I'll let you all know what I find out. Thanks for the comments and suggestions.

[QuailRiver]

Feb 16, 2017 3:06:20 GMT -5 Tien said:

Unfortunately I gave up on the stone. I have a friend who facets as well and he offered to take a shot at it and see if he has the same problem. Both my 1200 and 3k laps are resin bonded. I know topaz is an 8, harder than quartz, but it is taking far too long to work each facet on 3k. I'll let you all know what I find out. Thanks for the comments and suggestions.

Have you dressed your resin laps lately? All laps can get glazed over on the surface but resin laps are more prone to than plated and sintered metal laps. And once a resin lap gets glazed over they nearly cease to perform.

I occasionally use Nu-Bond laps and this is a frequent issue. I had to dress a couple of them just this week. With the Nu-Bond laps, the manufacturer recommends dressing with a piece if 220 grit silicon carbide cloth with the lap running at moderate speed, and use very light pressure (so not to embed any loose SC grit into the surface of the resin lap), and also they suggest to stay away from dressing the 1/4" of the outer edge so not to cut through the diamond and resin layer. Although they recommend SC cloth, I occasionally use a 220 grit SC dressing stick because it's easier to keep the lap surface flat with a long dressing stick than with SC cloth. But again have to be very careful not to embed loose SC grit into the surface of the lap. Also after dressing I rinse the lap well with water and then scrub it under running water with a nylon brush.

Also I never use Nu-Bond laps on anything harder than quartz. For 3k pre-polish (faceting) I still use a charged copper lap although I think most cutters are now using tin laps for 3k.

Larry C.

[Tien]

Feb 16, 2017 10:09:37 GMT -5 QuailRiver said:

Feb 16, 2017 3:06:20 GMT -5 Tien said:

Unfortunately I gave up on the stone. I have a friend who facets as well and he offered to take a shot at it and see if he has the same problem. Both my 1200 and 3k laps are resin bonded. I know topaz is an 8, harder than quartz, but it is taking far too long to work each facet on 3k. I'll let you all know what I find out. Thanks for the comments and suggestions.

Have you dressed your resin laps lately? All laps can get glazed over on the surface but resin laps are more prone to than plated and sintered metal laps. And once a resin lap gets glazed over they nearly cease to perform.

I occasionally use Nu-Bond laps and this is a frequent issue. I had to dress a couple of them just this week. With the Nu-Bond laps, the manufacturer recommends dressing with a piece if 220 grit silicon carbide cloth with the lap running at moderate speed, and use very light pressure (so not to embed any loose SC grit into the surface of the resin lap), and also they suggest to stay away from dressing the 1/4" of the outer edge so not to cut through the diamond and resin layer. Although they recommend SC cloth, I occasionally use a 220 grit SC dressing stick because it's easier to keep the lap surface flat with a long dressing stick than with SC cloth. But again have to be very careful not to embed loose SC grit into the surface of the lap. Also after dressing I rinse the lap well with water and then scrub it under running water with a nylon brush.

Also I never use Nu-Bond laps on anything harder than quartz. For 3k pre-polish (faceting) I still use a charged copper lap although I think most cutters are now using tin laps for 3k.

Larry C.

Thanks! This is good info. I may need to dress the lap. I was also considering a 3K steel or chargeable lap.

[QuailRiver]

Feb 16, 2017 10:34:54 GMT -5 Tien said:

Feb 16, 2017 10:09:37 GMT -5 QuailRiver said:

Have you dressed your resin laps lately? All laps can get glazed over on the surface but resin laps are more prone to than plated and sintered metal laps. And once a resin lap gets glazed over they nearly cease to perform.

I occasionally use Nu-Bond laps and this is a frequent issue. I had to dress a couple of them just this week. With the Nu-Bond laps, the manufacturer recommends dressing with a piece if 220 grit silicon carbide cloth with the lap running at moderate speed, and use very light pressure (so not to embed any loose SC grit into the surface of the resin lap), and also they suggest to stay away from dressing the 1/4" of the outer edge so not to cut through the diamond and resin layer. Although they recommend SC cloth, I occasionally use a 220 grit SC dressing stick because it's easier to keep the lap surface flat with a long dressing stick than with SC cloth. But again have to be very careful not to embed loose SC grit into the surface of the lap. Also after dressing I rinse the lap well with water and then scrub it under running water with a nylon brush.

Also I never use Nu-Bond laps on anything harder than quartz. For 3k pre-polish (faceting) I still use a charged copper lap although I think most cutters are now using tin laps for 3k.

Larry C.

Thanks! This is good info. I may need to dress the lap. I was also considering a 3K steel or chargeable lap.

I used to use a plated steel MAJA brand lap (not made anymore). It worked okay but if you looked at the finished stone under magnification there were always scratches left behind. Which is a complaint I have heard about other 3K plated laps. IMO rechargeable is the way to go.

I'm thinking about trying one of Gearloose's Zinc laps for pre-polish. From what I've read 8K on zinc works as well as 3K on tin or copper.

Larry C.

[micellular]

QuailRiver, I'm currently using Gearloose's Zinc+ (as part of the DiaZ+ banded lap) with 3k and oil. It works very well on harder stones, and quite good on quartz & softer. It leaves a slightly frostier finish on quartz than the harder stones, but Cerium Oxide on Diamatrix polishes relatively fast, maybe 30-60s per facet on a 6mm stone.

I first tried the 14k Blakstik with Zinc+ and found it prone to leave a streaky prepolish, but I was less experienced then.

[Tien]

Hi all,

I just remembered that I hadn't updated everyone on this thread. I finally got it figured out! The fix was not what I expected but it worked in seconds. I had to lower my speed to the lowest setting and use LOTS of pressure...much more then I would ever expect to for a resin bonded lap.

[micellular]

That makes sense. I can't run my laps at high speed, so I usually forget to specify low speed. And yes, my fingers cramped and had grooves from the pressure for a good half-day afterwards.

[pauls]

I cut quite a bit of Topaz.
My go to lap for prepolish is 3000 copper and/or 14000 on copper. I use WD40 as a lubricant and light pressure and things happen very quickly. Those two laps are the full thickness heavy copper laps.
I also have a lap made from a piece of printed circuit board which is charged with 1200, I use this to get the meet points very close to where they need to be, then get them right on with the 14k. So after the 1200 the surface is very fine, then the 3k or 14k brings a nice prepolish very quickly.
I don't use plated laps finer than 1000 they are too scratchy.
Another thing you will find with the thin plated laps is they are never flat. Best to get off them and get your meet points in on something that is flat, every step is then exact, just a touch and your surface is there, ready to move on.

Thats how I work, again its like everything we do in this hobby, suck it and see, if it doesn't work try something else.

[Deleted]

::not a faceter here::

It seems to me having to push down hard means there isn't enough grit to make the cut properly.

ETA or the lap surface is too soft and the grit is buried.

::End outsider observation::

[Tien]

Apr 7, 2017 16:59:49 GMT -5 @shotgunner said:

::not a faceter here::

It seems to me having to push down hard means there isn't enough grit to make the cut properly.

ETA or the lap surface is too soft and the grit is buried.

::End outsider observation::

I'd think the same thing but the lap is realtively new, has lits of grit left, and cuts other material just fine. It's definately odd, but i got it to work.