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Author Topic: Tumbling Cabs to finish  (Read 1649 times)

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William Phillips

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Tumbling Cabs to finish
« on: December 13, 2017, 02:44:20 PM »

Does anyone tumble their cabs after they have shaped the dome?
If so what grit do you start at?

Bill Phillips
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lapidaryrough

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Re: Tumbling Cabs to finish
« Reply #1 on: December 13, 2017, 04:53:46 PM »

grit, depends on your work.

  i use a vsv-45 vibra-sonic tumbler for shperes, cabs, fire agate rough  with garnets '' coreses grit i use in a vibra sonic is 220 grit.
 HighLand park   vibra 27'' plate lap 220 grit or finer!

  rotary's are for 40/70 - 80 grit for three week runs each.

 
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lithicbeads

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Re: Tumbling Cabs to finish
« Reply #2 on: December 13, 2017, 05:03:28 PM »

I always use sic belts to prep vibe tumbler runs. A perfect 100 grit sand is mandatory or if you have questions go to 220 then the vibe. After  220 grit I go to 600 grit and often clean the rocks after a day and repeat till they look very uniform. Prepolish is crucial and again do not be afraid to repeat.
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William Phillips

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Re: Tumbling Cabs to finish
« Reply #3 on: December 16, 2017, 06:13:14 AM »

Thank You

I am considering a Vibrator tumbler in the future. I have a Lortone 3 pound and a 20 pound also.

Bill Phillips
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kenny

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Re: Tumbling Cabs to finish
« Reply #4 on: December 16, 2017, 12:43:58 PM »

I take mine to 600 on the wheels figuring  my saw is cutting at about 400 maybe better or worse depending on how worn it is then I start the tumble with 600 to get the back finish close to the dome and go from there. 
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peruano

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Re: Tumbling Cabs to finish
« Reply #5 on: December 17, 2017, 09:19:44 AM »

A vibratory tumbler is the most time economical way to finish a cab (or hundreds of cabs).  They end up with backs polished as a extra benefit.  Often the vibe removes scratches that I would have ignored or missed. 
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irockhound

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Re: Tumbling Cabs to finish
« Reply #6 on: December 23, 2017, 10:20:06 AM »

The one thing about tumbled cabs is the soft edges.  Easy to tell tumble finished cabs as there are no crisp lines.  To me it takes away from the art and expertise of being a lapidary, bringing out a well finished sharp cab.  So easy to rough a shape and throw it in tumblers and let the tumbler be the lapidary, little skill required.  Whenever I see "Polished back" on the description I first think tumble finisher although some lapidaries do go to the length to make a perfect stone by also finishing the back but it always makes you wonder and I would guess that the more commonly polished back cab is tumble finished.  The soft edges and corners are the dead give away.  I almost always with a few exceptions try to keep a sharp hip line on my cabs between the dome and the bevel.  This is only a personal belief but I think it is one that a lot of cutters deal with in trying to justify why their cabs may be a higher quality than a machine finished cab.
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55fossil

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Re: Tumbling Cabs to finish
« Reply #7 on: December 23, 2017, 03:32:34 PM »

   Well, I agree with Irock on the tumbled finish takes away from being a more valuable cabochon. I hear many people ask about cabbing machines and tumblers so they can make a million cabochons, etc.  BUT, the polished backs and soft edges are done by many of us who make cabochons, by hand, from start to finish. The polished back can be hidden in a setting but still shows you took the time to do the full job on making a premium cabochon. As for "Soft Edges";  I set many of my cabochons in sterling silver settings. The soft (rounded) edges allow you to smooth the silver to the cabochon and looks quite beautiful (to me). IMO
    There is a place for tumbled finished cabochons and I do it myself on some stones. When you are in the trenches fighting to sell cabochons for under $25 you cannot spend 2 or 3 hours making a custom shaped cabochon with a flawless finish by hand. I shoot for $50 and up cabs but many times the stone cannot justify the price, even if it was hand made and hand polished from start to finish. Quality, beauty and type of stone will set the price. Sadly, a very small portion of the market will focus on the hand made cabochon which has not been treated in any way. I thank each and every one of them.
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irockhound

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Re: Tumbling Cabs to finish
« Reply #8 on: December 23, 2017, 06:15:53 PM »

I agree with all your points.  And I know you understand that I am not saying that soft edges and polished backs make a bad stone, it takes extra time as I noted for cutters to completely finish a stone.  It does make it hard to distinguish between a tumbled and hand rounded cab.  I can only feel your pain in trying to compete for sales.  I don't sell my stones so i don't deal with that part of the problem but I always wonder how sellers can make it with the cost of the rough, time spent in cabbing and then the marketing and shipping to compete with a 12 to 20 dollar stone, just crazy.  It is only my personal choice that letting a machine determine the finished cab diminishes the art.
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lapidaryrough

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Re: Tumbling Cabs to finish
« Reply #9 on: December 24, 2017, 02:18:09 PM »

When I see a 27 degree flat beveled edge of a cab.

what does a Competition cab looks like or right?

For the bezel cup you need the 27 degree edge for the prongs.

 
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gemfeller

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Re: Tumbling Cabs to finish
« Reply #10 on: December 24, 2017, 03:06:03 PM »

I agree with all your points.  And I know you understand that I am not saying that soft edges and polished backs make a bad stone, it takes extra time as I noted for cutters to completely finish a stone.  It does make it hard to distinguish between a tumbled and hand rounded cab.  ... It is only my personal choice that letting a machine determine the finished cab diminishes the art.
I don't find it all that difficult or time-consuming to polish cab backs.  It's part of my cutting routine because I never know if the stone will be set it in an open or closed back.  Sometimes it takes extra time to eliminate saw marks but I'm lucky that my saw leaves slabs semi-polished.

As for finishing cabs mechanically, if it's done right it's hard to tell tumbled cabs from hand-cut ones as you say.  There's very slight rounding of the girdle and back-bevel edges but as someone posted above, sometimes that happens with hand-cut stones.  That said, I only tumble cabs when I need a bunch for purposes where the difference won't be critical, like the dozens of family Christmas gifts I've been producing the past few weeks. 
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kenny

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Re: Tumbling Cabs to finish
« Reply #11 on: December 24, 2017, 03:44:13 PM »

Batch of tumbled cabs taken to 600 on wheels
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55fossil

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Re: Tumbling Cabs to finish
« Reply #12 on: December 24, 2017, 04:40:53 PM »

    It is not hard to compete with cheaper cabochons!  Many of my customers have bought from me for years. When I am actively selling quality cabochons I make sure and post cabs in multiple price points. Whether it is my web site or my Etsy page I make certain to note " hand cut and finished by seller". Also, most of my material is hand mined by myself. There are thousands of buyers in the market place looking for actual hand made cabochons. Many of my best customers are from overseas which really surprises me.

PS:  It takes more time and a lot of e-mails with customers in this market. So the extra time to polish the backs is pretty minor. These customers also do not ever come back if you deceive them about anything!!!!  I love that.
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William Phillips

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Re: Tumbling Cabs to finish
« Reply #13 on: December 30, 2017, 11:18:31 AM »

I have valued all that replyed to my post. I have always hand finished the cabs I have made and some I have finished the back side. Thank you for all the replies.

Bill
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irockhound

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Re: Tumbling Cabs to finish
« Reply #14 on: December 30, 2017, 01:09:20 PM »

After dragging it off topic I forgot to mention.  I agree that 600 is the best grit to start the tumble finish since if will give good results and will make the least change to the entry shape.  I know you said that you are looking at a Vibratory in the future and this is the best way since rotary tumblers are better at rough shaping and vibes are better at finish only work.  I really like the Ultra-Vibe tumblers and they are affordable and work very well.
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