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Sizing of cast rings?
Hello everyone!
I have a question (or two) for those of you more experienced with casting, since I have never had any done before.
Background is; I am making wedding and engagement rings for me and my girlfriend, so naturally I don't want to mess up too badly.
Since we are both not too fond of golden things I thought I'd have it cast in Palladium. So naturally I need to get it cast at a professional caster since I don't have the equipment to solder or cast it at home.
The rings themselves I will design using CAD, then let the caster print and cast it. (I have no experience of working with wax either, plus, it saves shipping costs). Since I know our measurements in mm it is also easy to adjust it in CAD.
According to a caster I spoke to there would be almost no shrinkage due to wax model and casting in Palladium, so that is good.
Now for the actual questions:
1) I will be using a court shaped ring (shallow curved on the inside) for all rings since it is more comfortable. However, my question is how this affects measurements. Since fingers are quite soft I would guess that the measurement would be using the maximum inner diameter more than the minimum inner diameter, since that is what will be pressed against the finger and it will become too loose if only using the minimum diameter.
So, would I make the rings a little bit smaller to match the maximum inner diameter, use the minimum or somewhere in between?
2) Finishing. I have seen a bit of reference that you will lose a bit of material to finish up a cast. The question is, how rough do they usually come out, how much do I need to polish away, and will it affect the size to a degree that I need to adjust for it?
I know I can make it a little bit smaller and then size it up a bit, but I don't want to make it too small or too big to begin with since it is the first time casting, and it will be a fairly expensive one at that. ;)
Do anyone have any (other) advice? :)
/Andreas
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As the caster says, although the tendency is for a casting to shrink into itself, so in theory it would end up a tiny amount bigger, in practice there is little in it. Also the inside finish will be pretty smooth, but will enlarge very slightly on polishing. So all in all you would make it no more than a half size smaller.
The real crux is that you must take the size with a sizer of the same profile and width as the final ring. Also it is wise to leave this test ring with the wearer for a week or two to be absolutely sure that they are happy with it.
As a result I recommend that you make a plain silver ring first to confirm the sizing, or risk painful resizing later. Dennis.
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Thank you.
Pretty much as I thought, the biggest issue is that my fiancee is located in Russia and I am in Sweden, so we don't see each other that often. I guess I will need to spend a bit on postage, both from the caster to me and then to Moscow.
She has tried on a few rings over there (and they do size in mm, so it is quite easy to make a CAD model out of it).
Still I would feel better if it was tested (and I can see how much I need to clean up the cast) before making the palladium ones.
/Andreas
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I always make the model half a size bigger and it depends on how you have the model made for clean up of its grown allow 0.1 to 0.2 mm for clean up depending on the how big the grown lines are if it's milled you won't need as much extra metal in my opinion on
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Well we have hit a snag in hat I was sure that the ring would end up a fraction big, but joseph who has more regular experience of cast rings says that it will end up a little smaller.
We need someone out there to adjudicate. Dennis.
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Great idea, and romantic too.. top marks.
I'm by no means an expert on such matters, although I do tend to cast a lot of things from wax models I make.
In my humble opinion, I reckon it'll shrink a little.. or at least thats my experience. Delft clay casting, and of course the more advanced centrifugal / lost wax casting methods should not leave too much clean up to do I would have thought. Casting into something like cuttlefish which is of course textured, does however require quite a bit of clean up on surfaces that are designed to be smooth.
Cheers,
Nick
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Well, this didn't really clarify much then. ;)
I would also think that it would have shrunk in to itself, making the ring a bit bigger, not smaller. Though I guess it makes sense for it to shrink a bit in diameter as well since it is a circle. I would think the investment somewhat stopped it from getting even smaller.
So to name an example: I want to make a ring in size N (17.1 mm), so according to Joseph (and Nick) I would make it as a size N½ (17.3 mm) with an added 0.1-0.2 mm thickness to compensate for cleaning up?
My brain sooo screams at me that it is wrong to make it bigger in order to get it smaller. ;)
It would be professionally cast since there is no way I could work with Palladium at home. :)
/Andreas
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Just to add to the confusion ;)
I often make a ring in silver (as the model), have a latex mould cut and have it professionally cast in gold. The clean up of the castings is minimal, I think allowing 0.1-0.2mm is about right. The rings definitely shrink and like Joseph & Nick I make the model half a size bigger to compensate.
(now the confusion!!)...I thought that the shrinkage occurred due to the latex mould, when it is heated and cools, so for instance you get minimal difference if using a silicone mould,.....therefore I am unsure whether you will get shrinkage if you are supplying the wax model....?? :confused:
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Nice of you to add a bit of confusion. ;)
The caster says the shrinkage is minimal with printing/milling to wax and then casting directly from it. I am unsure in what tolerances "minimal" is though.
I would need to compensate for the cleaning up though.
The plain rings are quite easy to make, so I will just need to decide on a size to cast them in, make them in silver and then try them out for size.
That said, I would rather have them a tad small so I can figure out how much I need to enlarge my model than to have to reduce it (since I don't have a rig for that).
As for the casting firm I talked to they don't have a finishing service. Perhaps I should have a dialogue with one that has it and they can tell me exactly how they would have done it if they were to finish it in house. :)
/Andreas
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4 Attachment(s)
Attachment 6737
I added a couple of test rings today too test the amount if any of shrinkage, the rings were both injected into the same rubber mould they were both size N
Attachment 6738
Our ring is the one on the bottom left to be cast in 18 ct white gold
Attachment 6739
also on the bottom left to be cast in platinum, No palladium this week so this is the closest test I can do
Attachment 6740
The amount of metal in the ring will also effect the outcome the more metal the more shrinkage I have found so there is no definite answer just an informed guess. As stated the bluer wax is injected from rubber / silicon moulds .The whiter wax is grown by a 3d printer, the surface finish of the grown wax is rougher than the blue as these are highly polished before the moulds are taken, this is why you should allow for more metal to be polished away. All been well I will post the cast rings tommorrow and we can see what happens. I will measure the rings up and check them against the cad to see the results
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You result will be the clincher, Josef.
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Wow, I would not expect anyone to cast rings just for testing, thanks a lot!
Will be exciting to see the results! :)
/Andreas
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Just to add more to the confusion, when measuring - for instance - hot hands, or "time of the month" can make a difference of a size or two.
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5 Attachment(s)
Attachment 6741
Raw castings trees
Attachment 6742
the wax model, 18 ct white gold, and platinum rings cut from the tree
Attachment 6743
The wax for comparison size N
Attachment 6744
Platinum raw casting M (ish)
Attachment 6745
White gold M(ish) bit of a wobbly cast that one !
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3 Attachment(s)
Attachment 6746
Both rings with the inside cleaned up ready for hallmarking
Attachment 6747
Platinum M 1/2
Attachment 6748
White gold M 1/2
Hope this helps
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So Josef, the rings became about one size smaller after casting, but removal of metal when polishing the inside caused them to end up a half size smaller.
This is what you predicted at the outset, when you said the wax should be a half size bigger than needed. However the The models made with a 3D printer are rougher than wax and need more finishing. So it is possible that rings cast from wax might need to start three quarters of a size bigger.
Also heavier rings will shrink more, so will need a further estimated allowance.
Thank you for clarifying the problem for us. I hope I have summarised it correctly. Dennis.
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That Josef is a really useful demonstration of the debate, thank you for taking the time to do it, document it and share!!
Very much appreciated :)
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Hi Dennis that sounds about right,but I still would only go half a size on average size grown rings as depending on which direction the rings are grown on the machine the grow lines effect it differently,I dont have a formula for this it just seems to work out ok. But if you need to make the ring to a certain dimension say for example a 3mm band its better to have a bit of meat on it to finish to the correct thickness so I would add a bit to the outer dimensions
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No problem Tabby glad to help. I just hope the ring fits Icarleug If Im in doubt I always go bigger at least she can put it on then get it resized as opposed to not putting it on and getting it resized !
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Really interesting thanks for sharing!
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Oh, yes it was very informational, thank you!
Now I at least know where to start when sizing and won't end up a size too small just because I wanted to be on the safe side (which was actually the wrong side)!
I think I will still cast it in silver first just to confirm the sizing and feel of the rings, even if it means it will be a tad more expensive. :)
Again thank you for going through the trouble of making, measuring and documenting the procedure, it was really appreciated!
/Andreas
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Oh, by the way, the plain rings are simple enough to make a bit bigger, but how about rings with heads/prongs?
Do you make them to size and then resize them with a factor, or you add a bit of width to everything, like gem sizes, prong thickness, etc to adjust for shrinkage?
/Andreas
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I make with the same allowance as the simple band (half a size), Andreas, but I do make sure that there is enough metal in the band to allow for adjustment through filing the inside of the ring or rolling the back, ensuring that the integrity of the setting is maintained.
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Thought of a new question (naturally) ;)
What kind of abrasive do you start with when cleaning the castings up?
All the way from white silicone (very coarse grit), or do you start with something a bit less agressive?
Using a micromotor, so I will probably go with mini-polishers of silicone or 3m radial wheels.
/Andreas
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There are endless ways to skin this rabbit Andreas, but for me the principle concern would be to preserve the court profile.
Wheels and flat things will most likely ruin the shape of the shank.
So, using your motor with as light a touch as possible and not staying still in one place, I would start with these:
http://www.cooksongold.com/Jewellery...prcode-999-ACR
and finish with these: http://www.cooksongold.com/category_...y=Radial+disks going through all the colours starting with yellow.
By the time you reach green, a final shine if necessary, could be effected by a polishing cloth. Dennis
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Thank you!
I already got the 3m discs and they are great!
I also have white and orange Luxi for final buffing and a good polishing cloth for all the nasty fingerprints. ;)
Just some scotchbrite wheels left then! :)
/Andreas
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By the way, how about tossing it into the rotary tumbler for some added work hardening and polishing?
I know I will still have to clean it up and do a bit of extra polishing and buffing afterwards, just curious to what it does to casted pieces.
Theoretically it would harden them I guess which would be good provided they do not need resizing on a mandrel...
/Andreas
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The consensus is that tumbling has a minimal effect on work hardening and then only on the surface. You also have the problem of needle marks.
To harden a cast ring without stretching or hammering, which might crack it, you can put it into a kiln at a set lowish temperature for some hours. Unfortunately I don't have the data, which is specific for each alloy. Dennis.
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2 Attachment(s)
Results!
I thought I'd pop in and tell the results of my first casting endeavor.
Firstly, I asked the casters how to size the ring and was told that I should make the CAD drawing to size, so I did, but added a tiny bit extra thickness to account for cleanup.
Supposedly their printing software accounted for metal shrinkage.
I was quite nervous when I got the rings and surely enough, one of them was miscast (Was slightly oval and about 17.4 mm in inside diameter instead of 17). I sent it back and they replaced it though, so credit for that, but it would have saved me postage and 1½ weeks of waiting if they had taken ten seconds of measuring it in quality control.
Rings looked quite dull grey when I got them, but were fairly smooth, not too bad artifacts from printing, I guess the Solidscape printer did a good job.
I proceeded with filing the remains of the sprue off the ring with grade 0, 2 and 4 files until it was smooth then headed over to my micromotor for polishing (I might want to get a real polishing motor the next time, it would probably go faster since I can just move the ring with two hands instead of coordinate ring and micromotor)
For polishing I smoothed the surface with silicon cylinders. I tried scotchbrite wheels, but didn't like it littering my workbench with dust, and I might have gotten a too fine brush as well.
I kind of expected it to be soft so I started gentle with the silicone. Found out quite soon that the palladium actually was quite hard, not at all like the sterling I had been polishing earlier so it took a lot more effort to get it nice and smooth.
Kind of guess that I need some more experience in polishing as well. I did work my way through white, black, blue and pink though.
After the surface was smooth I sanded the sides with wet sanding paper (400, 800 and 1200 grit), as well as smoothed them out with the silicon cylinders.
Then I used the mini 3m radial discs on the entire ring to ensure that there were no irregularities and the edges was smooth. Up from 400 grit to polish (Blue, Pink, Peach and Light Green).
Lastly used final buffing with Lux white and orange.
A new experience, and I guess you get better at it the more you do it. All in all I spent a better part of 10-12 hours of cleaning two rings, but hey, it is the first time and I had to do a bit of re-polishing due to scratches, plus that I was a bit too careful with my ring in the beginning and had some artifacts left from the casting and I needed to polish it all over again.
Will show a couple of images (just of my ring though, since my girlfriend is lurking here sometimes and I don't want her to see her ring just yet).
Attachment 6971
Ring from caster
Attachment 6972
Finished ring
/Andreas
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That's turned out nice Andreas, and you've got a good shine on it too.
Quick question though, why did you feel the need to have this ring cast when ( judging by the design of it ) you could have quite easily formed it yourself from the wire?
Nick
Sent from my iPad using Tapatalk
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Ah, it is made of Palladium 950. She didn't quite like the gold color of gold, and wanted a white shiny ring. Since white gold is mostly grey and need to be plated I figured we should go all the way and make it from Palladium instead. There will be a wedding ring cast as well (these are engagement rings (old Swedish tradition)) later, also in Palladium.
There is no way I could have soldered it at home, I don't have the equipment for it.
I am not entirely sure my landlord would like me to store hydrogen or acetylene bottles in my apartment. :)
Plus, wire + solder + equipment would cost a lot more than having it cast.
/Andreas
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Nice finish!
Incidentally have you seen the 9ct white gold that Cooksons do? its far less grey than 18ct, actually has a very slight yellowish tinge to it.
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Yes, I saw it and considered it for a while.
I would still need to buy solder and wire, and manage to make a nice shape ring out of it (basically a court shape with flattened sides) + a wedding ring (same style) later, with settings for stones.
This way it is a lot easier to make the wedding ring since I can adjust the thickness to be a little bit higher on the gem side which will make it fit well wit the other.
Plus, it is light and strong, won't oxidize and is a really nice color.
Since it is light it does not cost much more than a regular gold ring, and I still get to work at it a bit.
/Andreas
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Lots of work and a good result. Still, it takes fifty or sixty years to work at your marriage... Best wishes. Dennis.
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Turned out great nice job
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Thank you all! :)
/Andreas
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Very interesting thread to read.
Can I refresh it a little bit with one question that spins in my head for the last few days?
I see now how to make correct size of the ring, but how about bezels and other stone setting types? Should I make them bigger? How much %? How to calculate it? Well it’s easier with ring size as you can add more “meat” and then polish it, but I guess it is completely different with bezels and prongs, especially if you have shapes like pear or marquise.
Any thoughts, expirience?
Thanks!
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It's best not to think in percentages, because the difference in bezels and prongs will be slight, though important for a good fit.
Prongs of course can be moved a bit and bezels can be thickened and made slightly thicker for adjustment after casting.
Remember that stones of a nominal size will vary slightly when you measure them too, so have to be considered individually.
Dennis.