|Simplicity Oval 64 - Copyright 1997 by Jack Rowland|
|Difficulty level- Easy to Intermediate|
|Angles for R.I. = 1.54||79 facets + 16 facets on girdle = 95|
|2-fold, mirror-image symmetry||64 index|
|L/W = 1.218 T/W = 0.703 T/L = 0.577||P/W = 0.448 C/W = 0.142|
|H/W = (P+C)/W+0.02 = 0.610||P/H = 0.735 C/H = 0.232|
|Vol./W^3 = 0.263|
|g1||90.00||13-19-45-51||CAM 30.5 degrees|
|g2||90.00||09-23-41-55||CAM 31.75 degrees|
|g3||90.00||05-27-37-59||CAM 34 degrees|
|g4||90.00||02-30-34-62||CAM 35 degrees|
|c1||42.00||01-31-33-63||Cut to point|
|b1||45.00||02-30-34-62||Cut to g4-c1 meet|
|c2||42.00||16-48||Cut to girdle meet|
|c3||42.00||11-21-43-53||Cut to girdle meet|
|c4||42.00||07-25-39-57||Cut to girdle meet|
|c5||42.00||03-29-35-61||Cut to girdle meet|
|B1||35.00||02-30-34-62||Leave some girdle|
|M1||30.00||15-17-47-49||Cut to girdle meet|
|M2||32.00||08-24-40-56||Cut to girlde meet|
|M3||32.00||04-28-36-60||Cut to girdle meet|
|M4||32.00||64-32||Cut to girdle meet|
|S1||25.00||64-32||Cut to M4-B1 meet|
|S2||25.00||04-28-36-60||Cut to M4-S1-B1 meet|
|S3||25.00||08-24-40-56||Cut to S2-M2-M3 meet|
|S4||25.00||15-17-47-49||Cut to M1-M2-S3 meet|
|B2||34.50||13-19-45-51||Recut to S3-S4-M1 meet|
|B3||34.00||09-23-41-55||Recut to S3-S4-M1 meet|
|B4||34.20||05-27-37-59||Recut to S2-S3 meet|
|T||00.00||Table||Cut to proper S width|
|The oval outline is shaped via CAM preform settings given with each girdle setting. These should meet at the center point. The girdle is formed from these settings to form the oval. These facets are cut away.|
This is a variation on the Simplicity oval. I think it is an improvement over all and is even easier to cut with just as much brilliance. The reason for this design is to help out a friend who got a great deal on an old Lee facet machine, but he only has a 64 index. He can't get a 96 index. There aren't many oval designs that are set for a 64 index, so I though I might make him one.
To save the headache of cutting an oval shape by eye you cut the oval using a CAM preform. This is NOT some fancy attachment for your machine, it is a trick of 3 dimensional geometry that allows any girdle outline to be made. The facets used to establish the girdle outline are later cut away. The way you use this trick is to cut facets to a center point at the angles indicated with the girdle. As an example, set the index to 13,19,45,51 the angle to 30.5 and cut these facets to a common center point. Then cut index settings 9,23,41 and 55 at 31.75, all to the same center point. Keep on with all the girdle settings like this. Now you can level a girdle at each of these index settings and just like magic, you have a perfect oval outline!
The c1 culet facet is cut first. This must come to a point and cut off about 1/3 of the CAM facets to allow for the keel that will be formed by the other culet facets. Cut away a little more than you think you have too or you may have to go back and re-cut later. The culet break facets are cut to level the girdle at the point established by the c1 facets. The other culet facets are then cut at 42 degrees just to the girdle. When you polish the culet, be sure the lap is moving toward, not away from the keel. Any knife edge will chip if you polish with the lap moving way from the sharp edge.
The crown is cut but cutting a temporary set of break facets at 35 degrees at all the girdle index settings. This allows you have a place to see the proper point for the Main facets to go. All but B1 will be recut later. If find this trick very helpful for many designs. The M facets are cut to the girdle meets, the Star facets are then cut at the same index settings as the Mains. The S1 facet is cut to the M4-M3-B1 meet. The remainder of the Star facets are cut like a step cut all the way around using the last facet as a gauge to cut the next facet. Finally the Break facets are recut to the proper meetpoints. You may have to use some fine angle adjustments to get these just right.
Ovals take longer than rounds because of the extra adjustments that have to be made, but you need to cut ovals if you want to get more from your rough. All stones are not round. Give this one a shot, and I think you will find that there is nothing to fear from ovals!
Index of Gem Designs
Perfect Transfer Index
Table of Contents
© Bob's Rock Shop Bob Keller