Flatline by Bob Keller

Flatline Gemstone Design by Bob Keller

Flatline - designed by Bob Keller ©2015
Angles for R.I. = 1.54072 + 19 girdles = 91 facets
1-fold, mirror-image symmetry120 index
L/W = 1.012 T/W = 0.583 U/W = 0.528 P/W = 0.107 C/W = 0.107Vol./W^3 = 0.113

CAM Preform
cp25.50°15-45-75-105Cut to equal depth, establish temporary center point
130.78°011-109Meet TCP
231.65°013-107Meet TCP
331.93°015-105Meet TCP
431.63°019-101Meet TCP
530.99°021-099Meet TCP
628.16°029-091Meet TCP
726.57°037-083Meet TCP
826.00°045-075Meet TCP
928.69°057-063Meet TCP
1029.60°060Meet TCP
g190.00°011-109Set size, establish lower girdle line
g290.00°013-107Meet g1.1.2
g390.00°015-105Meet g2.2.3
g490.00°019-101Meet g3.3.4
g590.00°021-099Meet g4.4.5
g690.00°029-091Meet g5.5.6
g790.00°037-083Meet g6.6.7
g890.00°045-075Meet g7.7.8
g990.00°057-063Meet g8.8.9
g1090.00°060Meet g9.9.10
Pavilion
a29.14°011-109Match g1
b30.40°013-107Meet a.g1.g2
c30.61°015-105Meet b.g2.g3
d30.52°019-101Meet c.g3.g4
e29.84°021-099Meet d.g4.g5
f27.25°029-091Meet e.g5.g6
g25.53°037-083Meet f.g6.g7
h25.06°045-075Meet g.g7.g8
i26.96°057-063Meet h.g8.g9
j29.51°060Meet i.g9.g10
k28.87°012-108Meet g1.a.b.g2
l28.25°017-103Meet g3.c.d.g4
m24.21°025-095Meet g5.e.f.g6
n21.44°041-079Meet g7.g.h.g8
o23.53°014-106Meet k.b.c.l, k.a.a.k
p21.45°023-097Meet l.d.e.m
q16.63°038-082Meet m.f.g.n
r21.64°055-065Meet n.h.i, i.j.i
t 0.00°CuletMeet k.a.a.k, o.l.p, p.m.q, others
Crown
a29.14°011-109Match g1, establish upper girdle line
b30.40°013-107Meet a.g1.g2
c30.61°015-105Meet b.g2.g3
d30.52°019-101Meet c.g3.g4
e29.84°021-099Meet d.g4.g5
f27.25°029-091Meet e.g5.g6
g25.53°037-083Meet f.g6.g7
h25.06°045-075Meet g.g7.g8
i26.96°057-063Meet h.g8.g9
j29.51°060Meet i.g9.g10
k28.87°012-108Meet g1.a.b.g2
l28.25°017-103Meet g3.c.d.g4
m24.21°025-095Meet g5.e.f.g6
n21.44°041-079Meet g7.g.h.g8
o23.53°014-106Meet k.b.c.l, k.a.a.k
p21.45°023-097Meet l.d.e.m
q16.63°038-082Meet m.f.g.n
r21.64°055-065Meet n.h.i, i.j.i
t 0.00°TableMeet k.a.a.k, o.l.p, p.m.q, others

Download PDF format printer friendly cutting instructions: [ Download Icon Flatline Preform Printer Icon ]
Download PDF format printer friendly cutting instructions: [ Download Icon Flatline Printer Icon ]

Download the GemCad format design file: [ Download Icon flatline_preform.gem ]
Download the GemCad format design file: [ Download Icon flatline.gem ]

Flatline is a "flattened" variation of my Defibrilator 3 design for a heart shaped gemstone. Flatline works differently than Defibrillator 3 and other conventional gemstone designs that employ a pavilion designed to reflect and return light through the crown. Instead of a conventional pavilion, Flatline employs identical Defibrialtor 3 crown plan views on either side of the girdle with relatively large opposing tables and reduced crown angles.

The general idea is to intentionally window the stone to make use of rough material that is really too color saturated to work well as a conventional faceted gemstone without being reduced to melee in size. Another use of "flat" type designs is to make use of rough material that is too thin relative to the desired size of the stone to employ a reflecting pavilion. Assuming a girdle thickness of two percent (.02W), Flatline's finished depth is a little less than a quarter of its width (.234W). That's roughly two to three times thinner than typical faceted stone designs employing a conventional pavilion, which translates to roughly four to six times shorter internal ray paths and correspondingly less extinction.

Flatline isn't a design that you'll want to cut in clear quartz, except possibly as a proof or practice stone. It is intended to dangle so that light is able to pass through both sides of the stone and to capitalize on rich color. The most advantageous jewelry use of "flat" type designs of this type is probably as dangling earring stones.

Flatline Preform Perspective View

Flatline Cutting Notes

Flatline requires the use of a preform to first establish an accurate, repeatable outline shape and place its girdle facets so that its opposing crowns can be subsequently cut using a meetpoint sequence. Defibrilator 3 employs a single course, center point pavilion which was expeditiously translated to Flatline's shallower CAM preform via tangent ratio.

A temporary center point for the preform is first established by cutting four facets to equal depth at 25.50° on indexes 15-45-75-105. Preform courses 1 through 10 are then cut to meet with the temporary center point. Preform course g1 establishes the preform girdle line. Preform courses g2 through g10 are then chain cut to meet with each preceding preform girdle facet, creating the preform girdle line.

The angles of preform facets 1 through 10 were selected so that the preform girdle line can serve as a finished girdle line - the subsequently cut finished facets on the preform side nestle completely inside them. Using the preform girdle line as a finished girdle line, your rough must have a minimum thickness of .393W (.266W preform depth + .02W girdle thickness + .107W crown depth). If your rough is not at least a fat tad thicker than .393W, you may be able to extend its depth by gluing on a sacrificial piece of material, assuming the shape of your rough is conducive to this tactic.

Once the preform is satisfactorily cut, the preform side crown break facets a through j are cut to meet with their corresponding segments of the preform girdle line. Note that the temporary center point and preform facets 1 through 10 will all cut away as the preform side crown break facets are cut in. The preform side crown main facets k through n, crown star facets o through r, and the table facet t are then cut to meet per the diagram. After polishing the preform side crown, the stone is transferred and a matching crown is cut and polished on the opposite side.

If you cut a Flatline of your own, be sure and let me know what you've cut and how you made out.


Index of Gem Designs

Perfect Transfer Index

Table of Contents

Bob Keller