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does finger size affect ring durability?

nurse

Rough_Rock
Joined
Jan 15, 2011
Messages
32
Hello,
my partner and I have been discussing engagement rings lately and I've been lurking on here for a while trying to learn as much as possible. I've recently read some posts about how thin bands can be more prone to damage as opposed to thicker bands (greater than 2mm).

However I would like to know if the size of the finger also has any impact on durability. I have very small hands, finger size 3.25. To me it makes sense that a 1.8mm band would be more durable in a size 3 than say a size 8, mainly due to the smaller circumference size. I'm not really sure why I think that, I guess I just feel like the bigger the ring, the more stress is put on it (sorry if that doesn't quite make sense). I understand that regardless of how big or small my finger is, the thinner the band, the less durable it will be however I just want to know if having a ring of smaller size makes any difference. I am by no means an engineer/jeweller/trades person of any kind and may be completely wrong on this. However I was just curious and would like to know what others think.

prosumers, engineers and Jewellers feel free to weigh in and let me know if i'm right or wrong :)
 

yssie

Super_Ideal_Rock
Premium
Joined
Aug 14, 2009
Messages
20,540
nurse|1303415847|2902074 said:
Hello,
my partner and I have been discussing engagement rings lately and I've been lurking on here for a while trying to learn as much as possible. I've recently read some posts about how thin bands can be more prone to damage as opposed to thicker bands (greater than 2mm).

However I would like to know if the size of the finger also has any impact on durability. I have very small hands, finger size 3.25. To me it makes sense that a 1.8mm band would be more durable in a size 3 than say a size 8, mainly due to the smaller circumference size. I'm not really sure why I think that, I guess I just feel like the bigger the ring, the more stress is put on it (sorry if that doesn't quite make sense). I understand that regardless of how big or small my finger is, the thinner the band, the less durable it will be however I just want to know if having a ring of smaller size makes any difference. I am by no means an engineer/jeweller/trades person of any kind and may be completely wrong on this. However I was just curious and would like to know what others think.

prosumers, engineers and Jewellers feel free to weigh in and let me know if i'm right or wrong :)

Yup, just as you say.


First case: compression out-of-round (forcing the ring to go from a circle to an oval, but no lateral force so it stays in-plane - so if you put the ring down on a flat table the entirety of the oval touches the table) as buckling - going from the wiki entry -

Consider the portion of the ring under compression to be just a regular column, and assume plain bands, both made of same material, no structural defects like porosity to contend with, same circular cross-sectional diametre/area, only difference is circumference of the band (ring size):
F = EI(pi^2) / (KL^2)
F = critical force on the column, E = young's modulus - will stay the same, K = length factor constant depends on supports/L = unsupported length factor/KL = "effective length", I = plane inertia directly proportional to cross sectional area & configuration - will stay the same

So we have that if the effective length (KL) of this column of ring increases (increasing L for whatever K) the F required to cause bowing (buckling) decreases - rather dramatically, actually. Your instincts are right on - a smaller ring size will withstand something pushing it out of round better than a larger ring size, all else equal.



Second case: lateral pressure that's making it wave up and down if you put it on a flat surface. Same assumptions about shape/materials. Put the ring on the edge of the table and slide it off so that it's half off, and hold it firm. The push the other end down: the points on the two sides of the band that are right on the edge of the table are pivot points and the two lengths of ring that you're pushing on are levers.

torque = (F)(l)(sinA), angle and F are the same for both rings, l is length of lever, larger ring means longer lever l which means greater torque quantity. So again it's easier to torque a larger ring out-of-plane.



All that said, a size3 1.5mm pave'd band that is regularly worn is still a recipe for trouble ;))
 

kenny

Super_Ideal_Rock
Premium
Joined
Apr 30, 2005
Messages
28,175
All other things being equal, yes.

A ring of smaller diameter is stronger against forces in a certain direction than an identical ring of a larger diameter.

That said there is no black and white, safe vs. unsafe, dimension threshold.

Thicker is safer for all uses.
Thinner is less safe for all uses.

Being careful is more safe for all rings.
Being careless is less safe for all rings.

Thin and delicate is in fashion now, but just because a reputable jeweler makes a thin ring does not mean it will stand up to a lifetime of every day wear and tear.
 

Scorpioanne

Shiny_Rock
Joined
Oct 14, 2008
Messages
394
Yssie|1303422854|2902188 said:
[Yup, just as you say.


First case: compression out-of-round (forcing the ring to go from a circle to an oval, but no lateral force so it stays in-plane - so if you put the ring down on a flat table the entirety of the oval touches the table) as buckling - going from the wiki entry -

Consider the portion of the ring under compression to be just a regular column, and assume plain bands, both made of same material, no structural defects like porosity to contend with, same circular cross-sectional diametre/area, only difference is circumference of the band (ring size):
F = EI(pi^2) / (KL^2)
F = critical force on the column, E = young's modulus - will stay the same, K = length factor constant depends on supports/L = unsupported length factor/KL = "effective length", I = plane inertia directly proportional to cross sectional area & configuration - will stay the same

So we have that if the effective length (KL) of this column of ring increases (increasing L for whatever K) the F required to cause bowing (buckling) decreases - rather dramatically, actually. Your instincts are right on - a smaller ring size will withstand something pushing it out of round better than a larger ring size, all else equal.



Second case: lateral pressure that's making it wave up and down if you put it on a flat surface. Same assumptions about shape/materials. Put the ring on the edge of the table and slide it off so that it's half off, and hold it firm. The push the other end down: the points on the two sides of the band that are right on the edge of the table are pivot points and the two lengths of ring that you're pushing on are levers.

torque = (F)(l)(sinA), angle and F are the same for both rings, l is length of lever, larger ring means longer lever l which means greater torque quantity. So again it's easier to torque a larger ring out-of-plane.



All that said, a size3 1.5mm pave'd band that is regularly worn is still a recipe for trouble ;))
Yssie, are you an engineer? You know how to describe this so well!
 

yssie

Super_Ideal_Rock
Premium
Joined
Aug 14, 2009
Messages
20,540
;)) yes, indeedy
 

nurse

Rough_Rock
Joined
Jan 15, 2011
Messages
32
Thank you all for your answers!

I'll be honest Yssie, even though I didn't quite completely grasp the equation part of the explanation you did a great job explaining the science behind what I had just assumed to be 'common sense' or 'instinct' . You'd make a great engineering professor (or maybe you already are?) haha :)

I am contemplating a 2mm band that is pave about halfway (slightly less) down the shank and then widening to maybe about 2.2/2.5 at the bottom for extra weight/less spinning.

Kenny I agree with you, there is no black and white when it comes to durability of a ring. If I decide to go the thin/pave route I will probably need to take more care than if I were to choose a plain 3mm band. I was just curious what factor ring size played into the equation.

Again thanks very much for enlightening me !
 

mrssalvo

Super_Ideal_Rock
Joined
Jan 3, 2005
Messages
19,132
2mm for a pave ring should be fine. It's the super thin rings that are thinner than that I'd worry about. That said, any ring with diamonds on the shank needs to be cared for.
 

yssie

Super_Ideal_Rock
Premium
Joined
Aug 14, 2009
Messages
20,540

Haven

Super_Ideal_Rock
Joined
Feb 15, 2007
Messages
13,166
Very cool explanation, Yssie. (Not that I completely understood it, but I definitely appreciate it!)
 
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