Fixed Cutter Bits
Early Diamond Bit History
• Prior to 1940 natural diamonds were “peened”
into a steel head to create a diamond bit.
• Due to the high cost and marginal manufacturing
technique, diamond drill bit were rarely used.
• The primary diamond application was in core bits.
• 1947 - Christensen Develops matrix bit
technology for practical attachment of natural
diamonds to a drill or core bit head.
• 1954 - GE is the first to synthesize diamond.
• 1975 - First practical application of man-made
diamond with introduction of GE’s “Stratapax”
polycrystalline diamond compact (PDC) stud
• 1981 - Introduction of thermally stable
polycrystalline (TSP) cutters.
PDC Design Presentation
• Cutter Technology
• PDC Bit Design
• Profiles and Blades
• Cutter Orientations
• Bit Gauge
• Bit Mechanics
• Design Optimization
• Original diamond cutting element.
• Monocrystalline diamond.
• Different size and quality diamonds for different
• Size range expressed as stones per carat (SPC).
Natural Diamond Cutters
• Natural diamonds are
furnaced into the bit head.
• Versatile application range
when synthetic diamonds
are not applicable.
• Medium to very hard
• Fixed TFA.
• Thermally Stable Polycrystalline (TSP)
• Extension of PDC cutter technology.
• Cutter size expressed as stones per carat
• Thermal stability allows
cutters to be directly
furnaced into the bit.
• Developed for medium to
• Fixed Total Flow Area (TFA).
• Diamond grit is “hot-
pressed” into tungsten
carbide matrix to form
• Diamond grit is synthetic
• Pre-formed segments furnaced
directly into bit crown.
• Grinding tool for very hard and
• Especially effective at high
Conventional PDC Cutter
PDC Cutter Sizes
0.750” - 19 mm 0.529” - 13.3 mm 0.323” - 8.2 mm
0.642” - 16 mm
0.315” - 8 mm 0.315” - 8 mm
Carbide Supported Edge
CSE Cutter Standard Cutter
CSE Geometry Strengthens The Diamond
Edge Against The Cutting Force
Materials & Bit Construction
API Connection Stamp Area
- Serial #
- TFA - ND/Ballaset
Junk Slot Breaker Slot
Blank Crown Chamfer
PDC Gauge Nozzle
PDC Cutters Shoulder
• Bit profile and cutter layout are closely related.
• Layout is a compromise between the following:
• Maximum number of cutters (longer bit life)
• Lowest blade count (better hydraulics, penetration rate)
• Shortest possible profile (better bit stability and cleaning)
Volume of Rock Removed
• Volume of rock removed is a
• Cutter radius
• Depth of cut
• Width of cut
• There is a direct relationship
between the volume of rock
removed and the work rate of a
Volume of Rock Removed
• The volume of rock
5 removed is calculated for a
4 given penetration rate
(depth of cut).
• We use profile and blade
0 count to manipulate the
1 2 3 4
amount of work done in
60 RPM, 60 ft./hr each area of the bit.
Blade Count & Cutter Density
LIGHT MEDIUM HEAVY
• Tapered blades provide optimum
Blade strength and hydraulic efficiency
• The blade strength is calculated
Blade using the blade height, width,
length and the leading edge root
• Blade strength is given as a
percentage of the API connection
strength. (i.e., 204%)
Conventional Blade Configuration
Backrake & Siderake
Single Cutter Forces
Depth of Cut
F Torque Fn
• A cutter will see a different magnitude & direction of
forces depending on it’s location on the bit profile.
Resultant Cutter Force Vector
Group #1 Group #3 e
t Im bala
Force Vector Groups Force Vector Summation
• The gauge is considered the
stabilizing, full hole section of
• Gauge begins at the gauge
point and continues up to the
PDC Bit crown chamfer.
• Typical materials include
natural diamonds and
tungsten carbide segments.
• For optimum stability a flush
set gauge pad is used.
Anti-Whirl Force Balancing
• Cutter layout &
orientation are purposely
designed to create a net
imbalance force, pushing
the bit against the hole
wall and creating a
stable rotating condition.
Bit Dull / Other Characteristics
BC - Broken Cone LT - Lost Teeth/Cutters
BF - Bond Failure NR - Not Rerunnable
BT - Broken Teeth/Cutters OC - Off-Center Wear
BU - Balled Up PB - Pinched Bit
CC - Cracked Cone PN - Plugged Nozzle/Flow Area
CD - Cone Dragged RG - Rounded Gauge
CI - Cone Interference RO - Ring Out
CR - Cored RR - Rerunnable
CT - Chipped Teeth/Cutters SD - Shirttail Damage
ER - Erosion SS - Self-Sharpening Wear
FC - Flat Crested Wear TR - Tracking
HC - Heat Checking WO - Wash Out on Bit
JD - Junk Damage WT - Worn teeth/Cutters
LC - Lost Cone NO - No Other Major Dull
LN - Lost Nozzle Characteristics
Fixed Cutter Bit Profiles
A - All over
C - Cone - shown on all profiles
N - Nose - Part of profile that would rest on the table if bit set upside down
T – Taper – Straight portion tangent to nose and shoulder
S - Shoulder - Outer area adjacent to the nose and gauge areas
G - Gauge - Area ground to API specifications and cuts a “gauge” hole
We wish to thank the Hughes Christensen division
of Baker Hughes for their valuable assistance in
the preparation of this material.