TM 5-3820-256-10
NOTE
Drilling conditions dictate whether or not down-the-hole percussion tools are needed. (See FM 5-166 for
information regarding its use.) The percussion tool may be installed when first beginning to drill or after
some of the hole has been drilled using another drilling method. Regardless of when the decision is
made to use percussion tools, the down-the-hole (DTH) hammer and a button bit must be installed in
place of the tri-cone bit. If this means removing existing drill string from the hole, see "Coming out of the
hole," below.
CAUTION
When working around a hole that has been partially drilled, be careful not to drop anything down the
hole, especially metal objects (hammers, wrenches, handtools, etc.,) that cannot be drilled up. After the
drill string has been completely removed from the hole, install the drive plate onto the drive sleeve.
(1)
Assemble a button bit onto the bottom of the DTH hammer and a hoisting plug on the top. Use the auxiliary
drum to position the DTH hammer and bit assembly through the rotary hole. Use the break-out wrench to
hold the hammer.
NOTE
If drilling has not started yet, the hammer will come to rest on the ground inside the drive sleeve. If
drilling has already begun, the hammer will rest on the drive plate.
(2)
Remove the hoisting plug from the hammer and set it aside.
NOTE
If the hole has been drilled to some depth, you must insert the drill string first. It is, however, a good idea
to test the hammer's operation before lowering it all the way to the bottom of the hole. If you choose not
to test the hammer, insert the drill string (see "Going into the hole," below), then skip to Step 7.
(3)
Operate the hoist drum and lower the kelly (with kelly sub attached) into position over the hammer.
(4)
Rotate the rotary table to screw the hammer onto the kelly sub.
(5)
Test the hammer before drilling as follows:
(a) Turn on the air but not the rotation.
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