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KINGWELL Underreamer

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KINGWELL underreamer is a tool which could tripped into the hole to the desired depth for enlarging the hole while drilling, through reducing trip times to improve drilling rate.The expansion of its cutter arms are controlled by hydraulic force,so it’s convenient to realize open and closed of arms in drilling operation.

The underreamer is consists of Body(l),Top Sub(2),Cutters(3),Piston connector(5),P iston Stop sleeve(6),Jet sleeve(7),Seal ring(8),Set screw(9),Spring(10),Piston(ll),Left sliding block(12),Right sliding block(13),Clamp spring(14),Jet(15),Seal Assembly(16),Release screw(17),Piston extended shaft(18),Pin(19),Short screw (20) etc.
All the parts are machined from heat-treated high quality alloy steel,giving it exceptional strength to meet requirement of drilling under bad working condition. Cutters could be replaced by set are fixed on every cutter arm,the replace operation is easy and convenient with handle tools on drill floor. Three directional jets which could be replaced could fully clean the holes to increase the service life of cutters. It’s convenient to replace the jets which fixed by clamp springs.
The Underreamer adopt structure which piston rod connect with cutter arms,through hydraulic force to make them expand,compression springs to help them reset. In normal drilling operation, through fluid pressure drop create hydraulic force to drive piston connector and piston to move lengthways to make cutter arms open. Then cutters reaming the holes while rotating with drill string and the springs were compressed. When the pump stop circulating fluid,the compressed spring reset the piston rod,cutter arms back to body. Easy control of open and close of cutter arms and alloy insert of cutters make this Under Reamer with high efficient for reaming.

1.The piston locating sleeve of this Under Reamer need to be adjusted to the size required before trip into hole. (Sizes are showed in table 1) Steps are as follows:
Remove top sub(2),measure the distance(L) between piston locating sleeve(6) and body(l) by special gauge as the figure shows,then adjust the value of distance(L) to corresponding location of required reaming size,connect the top sub and body according to required makeup torque.
2.Check if there is looseness or big defect of cutters, screw it tightly in clockwise direction.
3.When trip into desired depth,increase displacement to make the pressure drop arrived 1.3Mpa,then the cutter arms will open and reaming. The recommend rotate speed is 70 to 110 R7M. It’s forbidden to reverse rotating the drill string to avoid cutters fall off.


1.Clean the surface and jet of this tool after pull out of the hole.
2.Take out the clamp spring from jet to check if it is need to be replaced.
3.Check each cutters assembly,change cutters which is damaged.
4.All the seals need to be replaced after used each time.
1)Remove short screw and pins.
2)Take out cutter arms,Left sliding block and right sliding block.
3)Remove top sub.
4)Take out springs and locating screw.
5)Screw the piston locating sleeve until thread is totally came out of body,then take out it together with piston connector from body.
6)Remove release screw,screw piston rod and piston locating sleeve from piston.
7)Remove clamp spring and seal assembly,take out the piston extended shaft from piton.
6.Assemble process is on the contrary.


1、Disassemble short screw (20) and Pin (19) in proper order when arms in closed condition.
2、Take out arms (4) Left sliding block (12) and Right sliding block (13) in proper order.
3、Use clamp spring plier to take out clamp spring (14) from Jet,then it can take out Jet (15).
4、Disassemble top sub (2) from body (1) and take out spring (10) and disassemble Set screw (9).
5、Rotating Piston stop sleeve (6) into internal thread of body until the thread completely come out and then takes out from body together with Piston connector(5) and Piston extended shaft(18).
6、Disassembly 17. Backing up screw,rotate out piston connector (5) and Piston stop sleeve (6) from Piston (11).
7、Disassemble Clamp spring (14) and Seal assembly (16),and take out Piston extended shaft (18) from piston
The assemble process of underreamer can do according to the reverse process of disassembly.
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