ready made chain descriptions on the cookies site.

[Green Monster]

The descriptions for the chains will often say something like "Sterling Silver 18/18 Curb 18"/45cm Unhallmarked"
sometimes the "18/18" part will be a single number, other times 2 different numbers, either way, to what do the numbers refer?

[mizgeorge]

It's how chain is sized. The first number is (rather oddly) a decimalised inch measurement and the second is the number of links per inch. So 18/18 is made from 0.018" diameter wire and there are 18 links per inch.

I know that these are traditional ways of showing size (though still find the decimal rather than fractional expression odd for an imperial measurement), but wish the information was also available in metric form, like everything else seems to be now, and was actually shown in the product descriptions - surely that wouldn't be too much to ask?

[Green Monster]

Great, thanks for the quick reply, just putting a website together so can get on with the descriptions now I know what I am talking about. :-)
Many thanks again.

[trialuser]

It's how chain is sized. The first number is (rather oddly) a decimalised inch measurement and the second is the number of links per inch. So 18/18 is made from 0.018" diameter wire and there are 18 links per inch.

I know that these are traditional ways of showing size (though still find the decimal rather than fractional expression odd for an imperial measurement), but wish the information was also available in metric form, like everything else seems to be now, and was actually shown in the product descriptions - surely that wouldn't be too much to ask?
Think of it as a thousandth (fractional) of an inch (thou), a fairly commonly used but admittedly outdated unit. 0.018 = 18 thou.
I didn't know that this is what the numbers indicated.

Edit. Don't be tempted, as I was, to look up a hair's breadth on Wikipedia!

[ps_bond]

A hare's breadth is about 4 inches, but it does depend on the hare.

Thous are used extensively in both PCB layout and machining still, although mostly hobbyist machining this side of the water.
I suppose thous are used a fair bit in religious texts too.