Kelly is located in the top of the drill string, with square and hexagonal. In rotary drilling, when it is drilling, kelly connected with square bushing and rotary bushing, transfer the ground rotary torque to Heavy Weight Drill Pipe and to drive the drill bit,bearing the weight of the drill string.In the drilling of the turbine and screw, the weight of the drill string and the counter torque are supported.

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Square Kelly Specification:

Specification Drive part length Overall length Drive part Upper internal threaded joint Lower external threaded joint Inner diameter

Standard

LD Selection

LD Standard  Selection Square size

DFL Across corner

DC Across corner

DCC Radius

RC Radius

RCC Eccentric hole minimum wall thickness Screw thread specification and  left rotate type Outside diameter Chamfering diameter Thread specification and type Outside diameter

DLR Length

LL Chamfering diameter

DF

Standard Selection Standard Selection  DU length LU Standard DF Selection DF

63.5 （2½） 11280 12190 63.5 83.3 82.55 7.9 41.3 11.43 （65/8）REG (4½)

REG 196.9 146.1 406.4 186.1 134.5 NC26

(23/8IF) 85.7 508 82.9 31.8

76.2 3 11280 12190 76.2 100 98.43 9.5 49.2 11.43 （65/8）REG (4½)

REG 196.9 146.1 406.4 186.1 134.5 NC31

(27/8IF) 104.8 508 100.4 44.5

88.9 （3½） 11280 12190 88.9 115.1 112.7 12.7 56.4 11.43 （65/8）REG (4½)

REG 196.9 146.1 406.4 186.1 134.5 NC38

(3½IF) 120.7 508 116.3 57.2

108 （4¼） 11280 15540 12190 16460 108 141.3 139.7 12.7 69.9 12.07 （65/8）REG (4½)

REG 196.9 146.1 406.4 186.1 134.5 NC46

(4IF) 158.8 508 145.3 71.4

108 （4¼） 11280 15540 12190 16460 108 141.3 139.7 12.7 69.9 12.07 （65/8）REG (4½)

REG 196.9 146.1 406.4 186.1 134.5 NC50

(4½IF) 161.9 508 154 71.4

133.4 （5¼） 11280 15540 12190 16460 133.4 175.4 171.45 15.9 85.7 15.88 （65/8）REG 196.9 406.4 186.1 5½FH 177.8 508 170.7 82.6

133.4 （5¼） 11280 15540 12190 16460 133.4 175.4 171.45 15.9 85.7 15.88 （65/8）REG 196.9 406.4 186.1 NC56 177.8 508 170.7 82.6

Hexagonal Kelly Specification mm（in):

Specification Drive part lengthти длины Overall length Drive part Upper internal threaded joint Lower external threaded joint Inner diameter

Standard

LD Selection

LD Standard Selection Square size

DFL Across corner

DC Across corner

DCC Radius

RC Radius

RCC Eccentric hole minimum wall thickness Screw thread specification and  left rotate type Outside diameter Chamfering diameter Thread specification and type Outside diameter

DLR Length

LL Chamfering diameter

DF

Standard Selection Standard DC Selection  DU length LU Standard DF Selection DF

63.5 （2½） 11280 12190 76.2 85.7 85.73 6.4 42.9 12.1 （65/8）REG (4½)

REG 196.9 146.1 406.4 186.1 134.5 NC26

(23/8IF) 85.7 508 82.9 31.8

76.2 3 11280 12190 88.9 100.8 100 6.4 50 13.3 （65/8）REG (4½)

REG 196.9 146.1 406.4 186.1 134.5 NC31

(27/8IF) 104.8 508 100.4 44.5

88.9 （3½） 11280 15540 12190 16460 108 122.2 121.44 9.9 60.7 15.9 （65/8）REG (4½)

REG 196.9 146.1 406.4 186.1 134.5 NC38

(3½IF) 120.7 508 116.3 57.2

108 （4¼） 11280 15540 12190 16460 133.4 151.6 149.86 9.5 75 15.9 （65/8）REG - 196.9 - 406.4 186.1 - NC46

(4IF) 158.8 508 145.3 71.4

108 （4¼） 11280 15540 12190 16460 133.4 151.6 149.86 9.5 75 15.9 （65/8）REG - 196.9 - 406.4 186.1 - NC50

(4½IF) 161.9 508 154 71.4

133.4 （5¼） 11280 15540 12190 16460 152.4 173 173.02 9.5 86.5 15.9 （65/8）REG - 196.9 - 406.4 186.1 - 5½FH 177.8 508 170.7 82.6

133.4 （5¼） 11280 15540 12190 16460 152.4 173 173.02 9.5 86.5 15.9 （65/8）REG - 196.9 - 406.4 186.1 - NC56 177.8 508 170.1 82.6

Steel Mark Chemical Composition%

C Si Mn P S Cr Mo Cu Al

4145H 0.42～0.48 0.15～0.35 0.90～1.20 ≤0.03 ≤0.03 0.90～1.20 0.15～0.25 ≤0.2 0.025～0.045

Other Elements：N≤0.015，Ni≤0.5

Mechanical Property:

Mechanical Property

Outside Diameter Range Yield Strength Tensile Strength Elongation

A%

HB Charpy impact 

Akv  J

mm in MPa Psi MPa Psi

79.4～171.4 3-1/8～6-3/4 ≥758 ≥110000 ≥96