Why rubies?

[ChrisM]

Noticed both my Tudors use rubies in the movements. Why?

[ar.parask13]

Rubies are used as bearings due to very low friction. I don't know if that helps...


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[Rameez-Q]

I'm sure most if not all automatic watches use rubies between parts to reduce friction.

A quick google will tell you everything you need to know

[ar.parask13]

It might worth adding that in the past they used to be genuine rubies... Nowadays they are synthetic...


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[Fredrik]

The friction coefficient between steel and ruby is very low. The rubies are synthetic, it is aluminium oxide.

[77T]

From wiki:
The advantages of jewel bearings include high accuracy, very small size and weight, low and predictable friction, good temperature stability, and the ability to operate without lubrication and in corrosive environments. They are known for their low kinetic friction and highly consistent static friction. The static coefficient of friction of brass-on-steel is 0.35, while that of sapphire-on-steel is 0.10–0.15. Sapphire surfaces are very hard and durable, with Mohs hardness of 9 and Knoop hardness of 1800, and can maintain smoothness over decades of use, thus reducing friction variability.



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[Tools]

They're just called "rubies" because they are red.

They are the same synthetic sapphire that your crystal is made from.

[watchgroupcorp]

Originally Posted by Fredrik

The friction coefficient between steel and ruby is very low. The rubies are synthetic, it is aluminium oxide.

Sapphire is also aluminum oxide... The sapphire in sapphire crystals is just heated up until it becomes a very, very hard "glass." Not too much unlike the process of making mineral glass crystals, except the aluminum oxide hardens into sapphire which can only be scratched by diamond, other sapphire, and probably a few other lesser known materials.

I have wondered if they make any sunglasses or eyeglasses out of synthetic sapphire to ensure the highest possible scratch resistance.

Also... I have a friend who believes that DLC coating is impenetrable and super strong and light weight. I told him that if that were the case, we should be seeing wonder woman's jet "The Wonder Jet" flying around.

I have experimented with Kliar nano-ceramic e-coating, and it is pretty cool. I noticed today that Fabrice Letellier posted a video of one of his Black Out Concept watches with a black ceramic coating on it and a customer was trying to damage it with a steel razor blade but couldn't... I'm getting a little off topic. #rambling

[ChrisM]

Thanks folks!

[crowncollection]

Good a answers above


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[dysondiver]

great answers , , some of the new hi tec nano stuff is amazing.

[drifter01]

Originally Posted by watchgroupcorp

I have wondered if they make any sunglasses or eyeglasses out of synthetic sapphire to ensure the highest possible scratch resistance.

No, sapphire is prone to shattering. This is the reason a lot of dive watches had mineral crystals rather than sapphire...shattering at depth. You wouldn't want your sunglasses to shatter into your eyes.

Aside: I realize that almost all dive watches have sapphire or quartz crystals now, but that is due to demand. People wanted scratch resistance.

[watchgroupcorp]

Originally Posted by drifter01

No, sapphire is prone to shattering. This is the reason a lot of dive watches had mineral crystals rather than sapphire...shattering at depth. You wouldn't want your sunglasses to shatter into your eyes.

Aside: I realize that almost all dive watches have sapphire or quartz crystals now, but that is due to demand. People wanted scratch resistance.

I think the best material is acrylic. It scratches, but then can be buffed. It's not impossible to crack it, but shattering it is nearly impossible. I'll take a plastic crystal any day for a watch. You're exactly right that sapphire will shatter and mineral crystals crack. The problem with the demand is that the average consumer hears "sapphire" and immediately imagines expensive gem stones. The same goes for rubies in a movement. It's more about marketing if you ask me. The best material for crystals is definitely acrylic. Hands down.

[drifter01]

I completely agree watchgroupcorp. Practically all my watches have acrylic crystals and it is one reason I prefer vintage watches. I think switching to mineral glass or sapphire was a bad move. They are more expensive to replace and can't be buffed out.

[subtona]

Lots of great info.

[watchgroupcorp]

Originally Posted by drifter01

I completely agree watchgroupcorp. Practically all my watches have acrylic crystals and it is one reason I prefer vintage watches. I think switching to mineral glass or sapphire was a bad move. They are more expensive to replace and can't be buffed out.

Plus the dial and hand damage that can occur with a shattered sapphire crystal can be pretty bad.