Milling Tools(1)- Junk mill

Pub Date:Apr 12, 2019    |    Views:99    |    


The Junk mill is a tool for milling downhole falling objects with the granular cemented carbide overlaid on the bottom. Used for milling drill bits, rollers, calipers, slip teeth, punches, drill tool joints, deep well pump parts, packers, water distributors and longer drill pipe and drill tools.


The Junk mill is composed of hardmetal particles surfacing on the mill shoe body. The upper small cylindrical body of the mill shoe is connected with the drill string by the top connection, and the bottom large cylindrical body and the side have a flume. The bottom flume has mud circulation hole, and the flume is surfacing with cemented carbide particles.

-Working principle

The hard alloy particles at the bottom of junk mill may bite into the falling objects under the action of drilling pressure, and then junk mill and the falling objects to produce relative rotation for grinding and milling, and the grinding falling objects are carried to the ground by circulating well fluid.


1 check whether the connection thread is intact and the water hole is unblocked before drilling

2 tighten the junk mill at the bottom of the drill string

3 down to 2~3m from the top of the object, open the pump to flush the top of the object, rotate the rotary table after the well head returns the liquid       smoothly, and slowly lower the drilling tool to contact the object.

4 properly pressurize and mill with well flushing fluid displacement not less than 25m3/ h.


After each use should be clean, rinse all debris in the water hole. Joint threads shall be coated with anti-corrosion grease, and wear protective wire, placed in a dry and ventilated place.

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