October 6, 2016 at 4:18 pm #2848
Our local gem and mineral club has acquired a faceting machine from an estate. We need to get cutting and polishing laps to use for demonstration and lessons (and eventual member use.)
1. I was thinking that a couple of toppers for cutting would be appropriate since they are inexpensive and would not create a crisis in the club if a novice did something wrong. Perhaps a 600 for cutting most facets and a 1200 for situations where a finer grit would be better? (I think we have a pretty coarse lap that would work for rough shaping.) Does this sound about right or would you suggest a different combination?
2. What about a lap for prepolish? I have been using a batt with 8000 or a 1200 d’Lite for that purpose. But either of those could be ruined by incorrectly indexed stone coming down on the lap. What would be appropriate for beginners?
3. Polishing — There is a ceramic lap that came with the machine. I don’t have fond memories of trying to get a super polish with that. I would expect that for most the initial materials will be quartz or glass. What would you suggest that would be safe with beginners and not too hard to master?
ThanksOctober 6, 2016 at 11:07 pm #2849
I think maybe you’re overly concerned about damaging laps. As long as your students understand that you don’t need a ton of pressure on the lap, BATT or Darkside should work well. I’d recommend 3K BATT for most prepolish, and Darkside with either diamond or oxides for polish. Both are easy to use and quite forgiving. As always, start the facet and then look to see if it’s working properly. Coating the desired facet with a Sharpie gives an instant indication that you have the right index.
Ceramic laps are tough, but even experienced faceters can find them difficult.October 7, 2016 at 6:02 pm #2850
Thanks for your thoughts. I would probably suggest that a ceramic lap is not just difficult, but close to impossible.
I personally like the batt for prepolish, but I would not like to deal with the ooops situation where a novice turns on the machine running the wrong way for the task at hand an brings down the stone with a bit too much enthusiasm.
From what I have read, the darkside does work well for many people when it comes to polish. I don’t happen to be one of them. But it may be the best bet for beginners. As you said, it is forgiving. Mistakes are unlikely to cause permanent damage to the lap as can be the case with other polishing laps. And the ability to switch from oxides to diamond and back is a plus for a situation where there may be more than one person sharing use of the faceting machine.October 8, 2016 at 1:54 am #2851
One suggestion – there is no compelling reason for a beginner to reverse the lap direction. I’d disable that feature. You don’t mention the machine brand or model, but it shouldn’t be difficult.October 8, 2016 at 3:42 pm #2854
It is a “Seattle” Fac-Ette Gem Master.
Reverse direction is used for the girdle and for the table.October 8, 2016 at 6:16 pm #2855
Interesting. Why?October 10, 2016 at 6:29 pm #2857
Reverse is used when doing the girdle (90 degrees on the protractor) and the table (0 degrees.)October 11, 2016 at 1:04 pm #2858
Yes, you said that. I still don’t know why.October 11, 2016 at 3:02 pm #2859
You don’t understand why running the lap in the normal direction would not be a problem at 0 and 90 degrees?
Remember that the Fac-Ette has that large protractor for changing the angle. I think that makes it a lot different than many other types of faceting machines. Generally for use, the stone is at the 6 o’clock position on the lap rather than 3 or 9 as I have seen for other makes. The result is that the direction of the lap goes with the facet height and spindle axis and is pulling away from the spindle. When you go to zero degrees, if the direction was not reversed, it would try to pull the stone from zero. Running in reverse, no fighting the lap directions as the hard stop keeps the table facet where it should be.
For the girdle, it seems a lot easier to control the stone when the lap is pulling away. Plus any splash that escapes is headed away from the user.
If that still doesn’t make sense to you, perhaps you can explain how it might be otherwise. I have only worked with Fac-Ette, so I am not familiar with the behavior of other machines.October 11, 2016 at 11:03 pm #2860
Interesting. I’d like to hear comments by other Fac-Ette users. On my machine, for instance, the cutting position is near 6 o’clock (on the operator’s side – is your clock different?) and the lap normally turns away from the stone position (left mast machine is CCW). For girdles, the cutting position may go as far as 8 o’clock. Some people reverse the lap if they’re having problems with polish, but that’s rarely necessary. Tables are cut with a table adapter, of course, and personally, I would use the adapter even on a Fac-Ette. If not, I suppose you might want the lap pushing the dop into the hard stop. I still don’t get the girdle problem.October 13, 2016 at 8:48 pm #2862
I do not use a table adapter. My experience with them was that they created more problems than they solved. (Some designs for table adapters are awful!)
When doing the girdle it is at the 9 o’clock position on my left mast machine.
For what it is worth, the owner’s manual provides instruction that the reverse direction is to be used for 0 and 90 degree situations.November 13, 2016 at 2:49 pm #2919
Being able to reverse the direction of the lap can be helpful when polishing. Sometimes the crystal structure of a stone being cut ends up being oriented in a direction on a facet where it polishes better in one direct than it does in another. The best analogy I can think of to compare this to would be wood grain. Wood cuts, planes, and sands much better with the grain than it does against the grain.
As for teaching beginners faceting – IMO keep it simple and inexpensive. Let them first learn to cut quartz or colored glass. 260, 600, 1200 laps or toppers, and a master lap to use with Spectra Ultra-Laps or Marsh Howard’s LL-Lite-Ceox Topper lap. I wouldn’t buy tin, batt or any other expensive laps to teach beginners on. I’ve seen too many beginners who would damage or ruin polishing laps by missing indexes and cutting into the surface of the lap with a sharp corner of the stone.
Larry CashattJune 16, 2017 at 1:27 am #3301
hi if you dont mind using a 6″ lap on an 8″ machine, by going on ebay and typing diamond laps i found a set of 3laps, 120 400 and 1200 for a total cost of $16 and have a whole lot more diamond on them than those made in u s , they are from china even the 8″ ers are cheaper. myself i’ve been using a pure tin lap with a quality 50,000 diamond powder made into a slurry on a SLOW turning lap with just enough drip to keep it as a mud. i’ve been polishing most stones that way for yrs. i have recently ordered a batt lap which they tell me is 90% tin, i will try it, i have also gotten a ceramic lap and is touchy/tricky to get to work. troublesome on large facets, on small stone and facet quite fast using tin oxide for quartz. but not functional with diamond compound or poweder. i like cutting large free form stones, right now doing a faceted egg in quartz, about 800 cts, the ceramic lap works but very low and trying. on you facet, i’ve cut on most all machines while working at crystalite/ pacific test specialties in the 70’s i demo’ed the facet for the maker then at a local lapidary show. you were speaking of moving the head straight up and down on the arched protractor yes you’ll have a problem. i would prefer to use a 45 degree adapter to get bettr control. only time i am concerned about spin direction is when you have a cleavage plain or growth plain to deal with. i use my ultra tec or my raytech as prefered machine.
michael zinski, 7302 w. yellowstone are, kennewick, wa.99336 1-509-783-9337 firstname.lastname@example.org been faceting and cabbing since 1965
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