You are correct,...measure across the underside.

Old K's varied in size. I had a "20" that measure 19 7/8 across as you noted.

But yes, across the underside is how to measure the dia.

Thanks Guys!!

Here is the email i was sent.

Hi, i have received the cymbal back thank you and have now issued a refund, just to be clear having checked with two cymbal experts one here and another in the US the correct way to measure a cymbal is across the bell making my description of 15'' correct, even though all the early K where measured in metrics anyway so they all vary, if you take the measurement from underneath it will obviously be less so even a modern cymbal say a 14'' hat with the 14'' clearly marked in print on top will measure 13.5 from underneath, just wanted to clarify the point. Regards.

He is wrong. Diameter, whether it be measuring a cymbal, the hole in the bottom of the toilet, or the nose cone of the space shuttle is the distance between the end points of a straight line that dissects a circle. Period. Not a line that is curved up and over a bell.

toodles

drumhack Mind Blowiflowers2baby crawl2Cool DudeMister T

In a totally hands on workshop like K. Zildjian was the intended diameter of a cymbal would be determined by the size of the ingot + how much it was milled. The milled plates ,derived from those ingots, which would be more or less 375mm (their version of 15") when done, were also stacked in order to receive the bell impression. This would cause a progression of bell depth .Flatter, shallower bells would be on the bottom of the stack. K's have bells anywhere from flat to pointed.. Deeper bells would account for a narrower cymbal----probably as much as 1/4" or more. This is one of the reasons that older K's are so inconsistent in diameters and seldom hit the inch size target that is expected but it is my understanding that you measure a straight line across the bottom. A 15" K. would be expected to be a bit shy anyway , by about 1/4".

There is an additional issue, especially when it comes to extremely thin cymbals. A cymbal during hammering is much more likely to exhibit small cracks at the edge than elsewhere. A solution for an edge crack would be to trim that off at the time the cymbal was dressed on the lathe. So a 375mm cymbal becomes a 370mm cymbal----still within bounds for a 15" in the maker's book. If the crack is a big one , then you've got a 14" cymbal now. Who's to know and the work isn't wasted.