faceting mistakes - tourmaline
faceting mistakes - tourmaline

How to Correct Faceting Mistakes


Faceting mistakes can cost gem cutters time and money. Learn some techniques for fixing common errors and making your repairs look like intentional designs.

6 Minute Read

Missed Index

One of the most common faceting mistakes we make is not setting the index correctly on our faceting machines. If you miss it by just one notch, it's enough to throw off the entire design.

Here's the diagram for a meetpoint oval being cut with a 64 index gear. You should cut the shaded facet at 44.7° and I 7, (followed by I 25, 39, and 57.)

correcting faceting mistakes - meetpoint oval

Now, say you make a mistake and cut it at I 8. If so, you should cut symmetrical facets all the way around, using indexes 24, 40, and 56.

How do you determine that?

The Solution

Simply add and subtract the proper number from your top and bottom index settings. This index gear has a setting of 64 (or 0) at the top and 32 at the bottom. We started with 8 from the top. Therefore, subtract 8 from 64 and you get 56. Add and subtract 8 from 32, the bottom center, and you get 24 and 40.

Your gem will look like this (with the new facets shaded).

meetpoint oval new facets

These appear off-center. You may think the gem will look better with split mains. Simply cutting a set at...


Donald Clark, CSM IMG

The late Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters “CSM” after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff’s ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book “Modern Faceting, the Easy Way.”

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