Pre polishing 14k Gold Castings

I have over 25 years experience as a jeweler & Metalsmith, primarily in sterling silver, but I do have concrete experience in working with 14 karat gold. A local jewelry designer recently contacted me wanting people with experience to assist her in “Pre Polishing” 14 karat gold castings in
preparation for stone setting . The other day I met with her and received samples of her castings. They are CAD/CAM designed, and cast from an outside source. All of her castings have a “skin“ that is extremely noticeable to the naked eye even (and look almost like cuttlefish cast texture with a loupe). Her work is very delicate, for example, tiny gold ear cuffs that would have diamonds set in them, prong settings for diamond earrings, and small gold basket pendant settings for emerald cut stones. I am looking for advice on the best methods for pre polishing these tiny, highly delicate castings in 14 kt gold that have this horrible textured skin” without removing the very delicate and intricate designs prior to stone setting. I have a flex shaft with lots of abrasive wheels, tiny buffs with various silhouettes and polishing compounds. I would appreciate some expert advice. Thank you!

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I’m of no use but I did want to say welcome! I hope you find the help you need. There are some great folks here.

Vibratory tumbling is likely the way to go. One tumbler with several bowls for progressive media and grits. Then finish in a magnetic pin tumbler.

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Thanks for the advice however I don’t have a tumbler (or access to one). Also this Jeweler is only needing a small handful of pieces pre-polished, so spending $$ on a tumbler & various media would be cost prohibitive. Do you have any advice for accomplishing with a flex shaft? Thx

Can you post a picture or two of what you’re talking about? That will help us problem-solve your dilemma.

I’m hoping that you’re not talking about the grow lines on the 3/D printed model, because those will probably have to be removed by some kind of abrasive media, which is complicated with a delicate object.



Do you live in a rural or a city area? There could be a jewelry club that has tumblers you could use?

I cleaned castings full time for years - a high end art jeweler. If the castings are terrible and pitted you are doomed.

But, if regular terrible cast8ngs then clean up parting lines and burrs etc with swiftly white or grey preposlish wheels. Contenti. Then they need a for real abrasive tumble. I ven tne cheapo barrel ones with good abras8ve media.

Unfortunately I cannot post photos. The items are super tiny. Yes I am talking about the grow lines on the 3/D printed model. Apparently they were cast at low resolution and the result was these layers of lines/ waves on the cast gold pieces.

No pits, no burrs. Just the texture of a 3-D printed model. I think the designer is concerned that the pieces are too small for tumbling and she wants me to try to clean them (pre polish) up via flex shaft. I have lots of various grit abrasive wheels from Rio. Perhaps I will try those. These items are super tiny though.

I cleaned the super tiniest of castings!! I kind of think it is all about holding them in work holder/parallel pliers whatever you can get away with and smoothing things, 8f it is art jewelry they are not looking for flawless just make it look ok and dint remove too much metal.

I use a work holder for almost everything…tint, tedious things, yes, you have o reposition constantly but you can get to it with abrasive wheels, you probably have wheels that will work and not be scary if you can make the tiny bits secure. Even a serrated parallel plier (yes, it,eaves marks) holds things well.

Post photos ok

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Ok I get it that you can’t show photos but maybe show us how you are holding things and the wheels you are using.

The designer should have sent in one piece for a quality check. And then she should have refused it. I wouldn’t take the clean up job if I were you. It’s a no win for everyone. The designer should take all of the pieces back and expect a refund or a credit for reprinting and hope that the contractor can resolve the issues.The models should have been printed with a different resolution and a different orientation.



i was thinking that same thing…maybe wrong resolution/ wrong machine for the job…i had interesting conversations with very knowledgeable people about this awhile back…and when things like this come up that is the first thing i think about…does the artist know what printer/ resin/ resolution/ orientation is being used…?…are printers forthcoming about these issues? are they knowledgeable about these issues…i am not knowledgeable at all…but i always wonder about the details…



So it turns out the designer is willing to shop around for the appropriate tumbler & media like you & others suggested. She has a double-barrel rotating tumbler (Is that appropriate?) that she took out of storage for me and asked me to research what type of media and grits to use (& perhaps also a magnetic tumbler). Could you kindly recommend what type of tumbler & media please? Thank you!

A Lortone tumbler? Hope so! Others will be way better at media recommendations but a few grits and then stainless shot. Maybe she has an extra barrel too?

also I covet a magnetic tumbler with extra fine shot because they are so fast and go into all the places so good!! Maybe you could have that in your tools… Super Finesse Jewelry tools is the one I have bookmarked somewhere but it is never in stock.

I know the problem re growth lines is not down to you but it can show a lack of experience on behalf of the designer if these are multiples of the same design. The idea would be to print out the original piece, clean it up and then make a mould for future items. Of course one would have to take into account the abrasive stages and shrinkage but I think the result would be better and the time taken in clean up would be greatly reduced.

If on the other hand the items are all unique pay no attention to the above and I think you would be correct in that the wrong method of printing was chosen.

I concur that if the grow lines or the skin of the casting is too great, this could be a lost cause.
That said, before you give up, you could try:
I’d do some pin polishing starting at a slow speed because you want to give a shine, not have the media impinge and scar the castings even more. Though, you state you do not own one.
You state holding is an issue - various options include copper wire hook or loop. String. Or,heat, bend, grind inexpensive pliers to grip. It can be as much of a challenge to position pieces as it is to keep them from flying it to the 4th dimension.
Thermoplastic for holding, from GRS, if you are doing steps that do NOT create a lot of heat. You can modify plier’s jaws with this for repetitive pieces.
For areas that round or knife edge abrasive wheels can’t get to, I’ve found the 3M Radial Bristle Discs to perform quite well. They go up in fineness enough to really polish a piece. Often use them around settings because they conforn to contours, while not damaging most stones. Sanding discs too. These types of abrasives come in various grits and are stocked at Contenti, as is thermoplastic. Rotary Abrasives - Abrasives - Finishing & Abrasives | Contenti
Do what I’ve done for years - stare at some tool catalogs trying hard to imagine how you might use some of them, even if in an unintended way for your job.
Good luck.

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