Forums Beginner Questions Table cutting

21 replies, 9 voices Last updated by tucsonbear 3 years, 1 month ago
Viewing 15 posts - 1 through 15 (of 22 total)
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  • #2643

    scottwkelley
    Participant
    @scottwkelley

    I am having an issue with the table cut leaning it seems to one side as though it is a little heavy to the center of the lap. I believe everything appears to be okay. I am using a facetron machine. Any suggestions on trouble shooting or is it technique.

    #2645

    carlshearer
    Participant
    @carlshearer

    well, i am not an expert, but everystone i cut has the table leaning to one side. you need to use the cheater to level it out and try and “make your meets”. of course , if it is way out then you have made some mistakes earlier in your cutting of the stone.

    #2646

    scottwkelley
    Participant
    @scottwkelley

    Thanks Carl,
    Yea it is really close where the meets are not going to happen at the same time. But it is close. I have yet to experiment with the cheat. Any suggestions as what to expect by going one way or the other and how much does it move.

    #2647

    Alan Balmer
    Keymaster
    @alanbalmer

    I don’t have a Facetron, so I can’t tell you off hand. But my answer is Experiment and Observe. For side to side tilt, coat the table with magic marker, then swipe it across the lap. Look at where the ink is rubbed off. Now change the cheater a bit and do it again. You’ll soon get comfortable with what direction and how much.

    For front to back tilt, do the same thing, but adjust the height of the head on he mast.

    #2648

    scottwkelley
    Participant
    @scottwkelley

    Very good Alan, thanks a bunch. My facetron has been darn near perfect but as I have been using it this has changed a little and I am glad I asked before thinking to try other things or giving up. It has been the front to back. I will do the ink test to figure it out.

    #2662

    carlshearer
    Participant
    @carlshearer

    yes, for me it has been trial and error and getting a feel for it eventually. but i suggest starting small, very little correction and see what happens. if you try to make to big a change at once you might be sorry.
    the problem of the facets not all lining up, even when you adjust with the cheater is a common one for me – in fact it is most of the time. this stems, i believe from not being as exact as we could be in our earlier meets – assuming you start with cutting the pavillion then any errors are greatly magnified by the time you get to the table.

    #2663

    scottwkelley
    Participant
    @scottwkelley

    Thanks Carl, I agree. I am very new and with every stone so far has been a learning experience and understanding the machine and what it can do is a challenge. Performing the cut to the drawing and polishing is fun and frustrating as each stone teaches me more about precision and quality. Everything hinges off the first cut and the placement of the dop. I am excited to send in the novice stone for evaluation. What is sad is I know more now since I cut it and feel I can do better already. Time is limited.

    #2669

    Tom Mitchell
    Keymaster
    @tommitchell

    Great discussion gentlemen. Every faceter needs to learn how to use the cheater to rotate the stone left to right and how to cheat top to bottom. Word of caution though. The cheater should only be used very sparingly. It should not be relied on to polish every facet.

    A post script to the discussion: when you are finally finished and have removed your stone from the quill, don’t forget to reset the cheater back to “0”. Facetron has very little play, left to right with it’s rotational cheater. If you forget to reset it back to “0” before beginning a new stone you may be out of luck if you need to use it on the next stone.

    Tom Mitchell
    Mitchell Jewelry Studio
    352-751-0906

    #2670

    Gregory Hays
    Participant
    @gregoryhays

    My machine is a late 90’s MDR PRO 300C. So the cheater is a invaluable tool and I had to lean to use it early on. I agree with Tom that you have to remember to reset to absolute zero before starting your next stone. Someday I may be allowed to trade in my dinosaur for one of the latest and greatest. But for now I will keep cheating away.
    Greg
    The Gem Garden
    San Marcos CA

    #2671

    Alan Balmer
    Keymaster
    @alanbalmer

    Greg, a new machine won’t spare you the cheating game 🙂 There will always be accumulated errors.

    There’s a nice illustration of the table adjustment process on page 192 of Tom Herbst’s book, “Amateur Gemstone Faceting, Volume 1: The Essentials. At a bit under $27, this book is the best faceting investment you’ll ever make.

    #2672

    scottwkelley
    Participant
    @scottwkelley

    At the time I am cutting a large piece with large facets, wide and long. I am taking the opportunity using large facets to learn this cheat method and to understand great polishing. I marked my formed facet with black perminant marker and colored it in. What I found was very enlightening. I then and will start using this method a little more often to let me know which way to go as I don’t have enough experience to tell by eye. My machine doesn’t require a lot of adjustment but my laps appear to have have the front to back adjustment depending where I polish on the lap. The longer the facet the front to back on the 96 and as close to the hard stop seems to make huge differences in the polish. Now how to detect minor scratches before the 1200 lap.

    #2673

    carlshearer
    Participant
    @carlshearer

    the other thing that i have found with my facetron is that the “zero” on the cheater is not the actual zero, it is off a little. i dont know how or why but it is . discovering that saved me alot of work.

    #2675

    Tom Maxwell
    Participant
    @tmax

    Hi Carl,

    Check out John Baily’s U-Tube video – https://www.youtube.com/watch?v=EvinThs_LQw
    This should help a lot!

    Tom Maxwell

    #2676

    carlshearer
    Participant
    @carlshearer

    Thanks Tom, i have seen that video already. i agree it is excellent!

    #2705

    michaelnoetzel
    Participant
    @michaelnoetzel

    Scott, I have a Facetron. The use of a cheater adjustment is invaluable for you to level your table and get it to meet adjacent facets. First off you need to have the machine itself zeroed out before you ever begin. Install the 45° adapter that you would use to cut and polish the table and lay it down on a clean polishing lap or master lap with the machine set at 45° and a 96/0 index (zero I dex on whatever gear you are using). You will have to raise or lower the quill with the fine adjustment so that the adapter is JUST sitting on the lap (I have a ceramic lap I like to use, because it is solid and absolutely flat). The cheater should be set at EXACTLY zero. I even make a tiny mark on the silver dial right next to the tick mark on the anodized area to the right so you can see them line up just that much better. Also, make note that the grooved piece of metal that points to the index mark (say the 96 mark on a 96 gear) is centered in the channel is rests in. There should be an equal amount of space on each side; about 1/8″ or so.

    If you can slip a piece of paper (find some sheet of fine grained paper like a glossy magazine or smooth office paper to use as a shim stock or an actual piece of shim if you have one), your cheater is not zeroed. Don’t move the cheater, make the adjustment with the star nut that holds the index gear in place. You need an Allen wrench for this. Loosten the nut and the adapter will twist left and right. What satisfied, tighted the nut. Take a really long time making sure this is as accurate as you can do it.

    When you next go to cut a new stone, if your machine is zeroed perfectly, when you start cutting your girdle, you shouldn’t have to adjust your girdle at all for all facets to line up as you go round (meaning to use the cheater). Depending on your level of skill and equipment (power eye loupe, head visor or microscope), as you do this each facet will be microscopically a little higher or lower than it should be but do your very best to line up each corner one at a time.

    The art of gemstone cutting reflects the skill of the faceter to line up not only the girdle facets but all others until you finally get to the table. It is pretty much impossible to get to the point of cutting and polishing the table and not have to use the cheater because of the microscopic faults in lining up all your previous facets. It’s just a part of the process that you need to master but if your machine was properly zeroed from the beginning and you’ve been attentive to lining every facet up pretty well, the amount of cheating should be kept to a minimum. You should not be able to visually see that a table (that is supposed to be level by design) is tilted: ever. But our vision typically is not good enough to see minor cheats.

    The cheater on the Facetron machines are marked 0-7. With your stone in the adapter, pivot the quill uptight to inspect the table. As you pointed out marking the stone with Sharpie markers before you cut or polish will let you see where the grinding of the stone is actually taking place. If you find that you have to tilt the stone so that it cuts/polishes a little more on the left, adjust the silver cheater -‘downward’ so that you are going from the zero mark down to seven or so. Maybe more or less, you have to figure out how much.

    If you need to cut more to the right, you ‘go up’, meaning your adjustment would go from zero to one. If you need to shave more off the top or bottom of the stone that is the height adjustment and not the cheater. Mastering the cheater takes some time but is critical to improving your abilities.

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