Chisel Point

The chisel point is constructed like the moil point except for its point (fig. 14- 14). This point makes the

Figure 14-14.-Air hammer attachments.

chisel point the best to use for trimming corners and splitting seamed rock. Also, when you run into hardpan in trenching or at the bottom of a construction project, you can use the chisel point to slice off rock to reach the desired grade elevation.

Asphalt Cutter

The primary use of the asphalt cutter is to trim or cut the edges of laid asphalt, so major excavation will not harm the existing surface. One good example is asphalt patchwork.

Clay Spade

The clay spade is used for loosening compacted clay or dressing foundation edges.

HAND-HELD ROTARY ROCK DRILL/JACKHAMMER

The hand-held pneumatic rock drill/jackhammer (fig. 14-15) is a piston rotary unit that is designed mainly for use as a hard rock drill; however, it is equally efficient in soft and medium formations.

The components of the drill are shown in figure 14-16. The drill consists of a back head group, cylinder unit, and front head group. The back head group consists of the four-position throttle, handle, and live air inlet. The cylinder unit consists of a cylinder with a reciprocating piston. The front head group consists of the chuck, retainer latch, and anvil. The drill design directs air through the drill, down the drill steel, and into the bottom of the hole to blow out rock cuttings.

Four classes of rotary rock drills/jackhammers are as follows:

. The first class is a light drill, weighing about 15 pounds. This class is used for drilling shallow holes in quarry operations.

l The second class is a light drill, weighing 25 to 40 pounds. This class is used for light work, such as potholing and drilling concrete.

. The third class weighs from 40 to 50 pounds.

This class is used for drilling in limestone and other soft rock.

. The fourth class is a hand-held drill, weighing from 50 to 65 pounds. This class is used for drilling holes up to 6 feet during quarry operations.

NOTE: All of these drills use hollow drill steel and are built with automatic rotation.

Figure 14-16.-Components of a hand-held rotary rock ^{drill/jackhammer.}

Figure 14-15.-Hand-held rotary rock drill/jackhammer.

Hand-held rotary rock drills used in quarry operations may be the dry drill, the blower drill, or the wet drill.

The dry drill allows very little air to pass through the drill steel while drilling; therefore, you should drill 30 seconds and blow 60 seconds. When the hammer is not running, the dry drill allows enough air to pass through for cuttings to be blown out of the hole. Drill steels for this drill comes in lengths of 2, 4, and 6 feet with tips made of carbon inserts, diamond, or star.

The blower drill allows a steady supply of air to pass through the drill steel to help remove cuttings from the hole while the hammer is running. This type also permits air to pass through ths drill steel when the hammer is not running.

The wet drill provides a constant supply of water through the drill steel while the hammer is running.