I've seen some oval bezel stone-setting in my many years. In this essay, I will not copy them, these following techniques are my own FOR YOU TO COPY.
I use only one style of burs in this style of setting. This bur is a 156 High-Speed Steel, otherwise known as "156 HSS".
If you use a "156 Carbide" bur you will find that the teeth of the bur very close together and are not aggressive enough to cut into the metal. The teeth only skim along the surface and don't prepare for accurate and intense cutting that is needed here.
The hammering process needs to follow one rule. This rule is to hammer at a prescribed sequence of events.
If the hammering starts at #7-9-11 then followed by #12-8-10 on this diagram. The results will be catastrophic with the stone being 'crooked and slanted' in it's bezel.
This rule as now shown requires that the hitting process is initiated at #1-2 => then #3-4 => then finally #5-6. THIS IS THE SEQUENCE TO FOLLOW with no deviations, nor shortcuts!
When the hammering has started, remember that THERE MUST NOT BE ANY SPACES BETWEEN THE STONE AND THE METAL. The Bezel must be flush with the stone.
If the stone has a deep Culet, then that Culet should be placed upon the steel mandrel and the Culet must be placed where the Mandrel groove is situated.
This hammer was not to be used for gentle Bezel Setting, why not? First of all, it is too heavy. The setter's view is totally obscured and the setter cannot see where the hitting is being done.
This hammer is still too heavy, but under certain circumstances, it could be used for more aggressive stone setting.
You can see where the Culet of the stone is almost resting against the mandrel, but not touching the steel.
If the Culet is damaged, WOOPS. You should remove the stone and replace it immediately...GOODBYE $$$.00
You could use a round bur to carve a 'bearing' groove and prepare to set the stone. There will be problems if you choose this process, why is that?
The new bearing will not be deep enough into the metal or allow the girdle of the stone to fit into the bezel. The next problem is that the girdle will not be at the same width for the stone either.
If the round bur is your choice of cutting there is a b-i-g problem starting, The stone could be set crooked or tilted, THIS CAN BE A MAJOR PROBLEM. To avoid the problem please use a "156-HSS" cutting bur.
Here is the result of using a round bur, this stone is crooked!
You have little control in making a bearing cut 1) deep into the metal. 2) uniform in girdle width all around the bezel. 3) allowing the metal to be at the same difference from the bezel tip to where the girdle will be. The result is DON'T USE A ROUND BUR.
Before you start to hammer the tip of the bezel, place the Culet into the mandrel opening.
This oval stone is almost acceptable as it is 'slightly tilted'.
I changed the position of the hammer anvil tas it is gently 'moving' more metal along the bezel.
In this close-up photo, you can now see the piece of metal being removed while the cutting action is in operation.
After the stone is secured and tightened, I'd gently use a wide file of a #4 grit to evenly clean the hammered area flat.
I enjoy using the Pumice Wheel of #180 grit to smooth the top of the above bezel wall from all of the hitting. You can see the slight angle being given to the bezel tip.
From this angle, the stone is nice and flat.
I'm using a Reciprocating Hammer, you can see that the anvil is not touching the stone. It is gently 'moving the metal' towards the stone.
I always use a Flat graver to "Bright-Cut" the inside of the Bezel wall.
I'll finish the cleaning of the bezel but using a PINK Pumice Wheel of #1,200 grit. Instead of using a cloth polishing wheel that can round off any edges, I chose to manually 'save the edges' that give a great finish to the bezel.
I continued to clean the main section of the ring with a "Medium" grit of my "Snap-on, Emery" wheel. This will give a nice finish where it's needed.
During the overall cleaning, I will examine any defects from the metal casting and repair them NOW!
Inside this ring I noticed a few casting problems, these must be repaired NOW.