#YAW PTERM CUT HOW TO#

An shift in the azimuth direction will be like moving from one position in a circle to another. Now the azimuthual direction is also known as the ‘hoop’ or circular direction that is the direction you would be walking if you were walking in a circle. The result of the cutter’s techniques to correct the facet meet-points causes what is referred to as ‘azimuth shift’. At the new angle, the facets would normally not meet nicely at the girdle. One side of the facet has more material removed from it causing the facet angle to change. The problem cutting from the east west direction is that it causes one side of the facet to spend a bit more time in contact with the cutting wheel than the other side. This marks the most important difference between yaw and indexing, because indexing is still cutting from the north south direction. One occasion where yaw can occur is when the cutter finds it impossible to cut in the north south direction and the cutter is forced to take material away from the east west direction.

Sometimes it is literally impossible to cut a diamond along a certain plane and this results in polishing issues.

The trick is that diamond’s hardness is directional, meaning it is more difficult to cut in certain directional planes than others. The reason is because only another diamond can cut a diamond and even then, cutters need to take advantages in the crystal structure in order to cut a diamond with another diamond. The hardness of diamond makes it a challenge to cut. The starting point is usually at the girdle cutting either north or south. Diamond facets are usually polished with the cutting wheel spinning in the east west direction (relative to the facet) and the diamond is moved into contact with the cutting wheel where material is removed normally from a north south direction (north being towards the crown side).

Twist can be either due to indexing or yaw To understand what yaw is you need to know why yaw occurs, and to do that you need to know a bit about how a diamond is polished.

Distortion includes any misalignment or twist.

The actual concepts are similar and I like to think of indexing and yaw to both twist the facet. Yaw is also sometimes referred to as a twist, but the twisting of facets is more commonly referred to as facet indexing, which we discussed in depth in the tutorials on the upper girdles. Yaw does cause a distortion in the diamond, but it is important to understand that not all distortion is caused by yaw. Curved facets require a constant change in slope but a single change in slope can cause a yawed facet. It also does not mean that the facet is curved, at least not a smooth curve. Facet yaw in diamonds is not a rotation of the facet around its central axis (the axis created by a line that bisects the facet). (This is a picture from the Wikimedia Commons, a freely licensed media file repository.) Lets get it straight right off the bat. Those of us who are familiar with airplanes or gyroscopes will know that the other axes are named pitch (y-axis) and roll (x-axis). In engineering, yaw refers to a rotation in the corresponding z-axis. Yaw is a confusing term primarily because it is difficult to visualise and secondly because of its naming. In the industry, the term ‘cheated’ is sometimes used referring to the facet where swindling strategies was used.

Like painting of the girdle, yawing is therefore potentially a swindling strategy. The technique of yawing a facet can be used to tweak the diamond’s proportions while maintaining the lab-graded symmetry grade. What is Facet Yaw?įacet yaw, a term coined by Brian Gavin, is a type of facet distortion that can occur either through poor cutting or tricky cutting. I will also try to clear up the confusion regarding this topic in relation to the terms yaw, twist, distortion, and azimuth shift.

#YAW PTERM CUT HOW TO#

This tutorial aims to explain what yaw is, why it occurs, how it occurs, how to detect it, and how it affects the appearance of a diamond.

Yaw pterm cut