Hand Drilling and Breaking Rock for Wilderness Trail Maintenance

Drilling

Always wear safety equipment, including safety glasses or goggles and gloves, when drilling.

1. A special, short-handled hammer called a single jack is used for one-handed drilling. Hammer heads weigh either 3 or 4 pounds, and handles are 10 inches long. The short handle helps you place blows accurately.

Single jack driller at work.

A long-handled single jack, an engineer's hammer with a 14 inch handle and a 3- or 4-pound head, for example, can be' used for two-handed drilling with another worker holding the steel. The proximity of both hands to the steel required by the handle assures that accuracy and safety are not sacrificed. We call this technique modified double jacking.

2. The driller will be kneeling on one or both knees, or sitting. If modified double jacking is used, the holder should position himself across the steel from the driller, and wear gloves on both hands.

Modified double jack drilling team at work.

Assume a comfortable position and change positions and tasks regularly to help minimize stiffness in legs, arms, and back. Knee pads could be an asset.

3. Grasp the hammer firmly and hit the steel squarely. When collaring (starting) a hole, work deliberately and slowly, placing each blow carefully. Although a drill hole is usually started with a drilling steel, it can also be started by chipping slightly with a pick. In the beginning dust and rock chips are difficult to minimize. Be patient when collaring; a hammering rhythm is much easier to maintain after the hole has been started.

Establish your rhythm as soon as possible. Drilling with a regular rhythm will be more productive than driving the steel with powerful strokes in sporadic bursts of effort. Hard hitting causes you to tire quickly and experience cramping prematurely. It also causes the steel to stick in the hole. Take frequent rests to prevent cramps, and do not ignore signs of fatigue. Let the tools and gravity do the work.

Any rest that can be afforded your 'hammer-holding' hand while single jacking will help conserve your energy. A wrist thong may be attached to the end of the handle to help drill at unusual or difficult angles. The thong is looped around your wrist and lets you rest your grip a moment after each stroke. On the backstoke the fingers may be opened and the grip relaxed, allowing the handle to swing free but restrained from dropping by the thong. At the end of the backstroke the fingers close around the handle to prepare for the next swing.

Old time miner using a single jack equipped with
wrist thong, early 1800's.

4. A hole is drilled because rock is chipped by the concussion of the bit from the blow of the hammer. Grip the steel firmly but not tightly during each blow. Hand drilling produces very little shock in the 'steel-holding' hand. The holder in a modified double jacking operation will also find that only a small amount of shock is transmitted from the blow of the hammer. Always wear gloves while holding, in case of a glancing blow.

After each stroke, turn the drill about 1/8-revolution; this is called 'shaking' the steel. Drill steel is usually octagonal in shape, so turn the steel so the next flat side faces you. There is a slight recoil of the steel after each blow, and it is after the recoil that shaking is performed. Lift the steel slightly before turning. If the steel is not turned, the bit will sink straight into the cut and jam in the hole. When shaking, allow your grip to relax slightly after each rotation. Regain your grip before the next blow.

Difficulty in shaking the steel, especially in 'down' holes, indicates that the rock dust in the bottom interferes with the cutting edge of the bit against the rock. With two hands turning the steel, teams may go for longer periods before clearing cuttings from the hole. Water is helpful for removing cuttings from holes.

5. Regularly add small amounts of water to minimize dust from drilling and keep the drill steel cool and the temper intact. This keeps particles in 'down' holes in solution so they won't hinder the progress of the drill. Water creates a mud that sticks to the steel and is withdrawn from the hole with the steel. The adhering mud is removed by rapping the steel sharply against the rock. Holes are periodically flushed clean by bouncing the steel in the hole while adding water to create an agitating motion. The generous use of water allows the drilling action to force cuttings out of the hole as quickly as they are generated. Minimize unpleasant splashing by wrapping a small rag around the rod at the top of the hole. Keep the rag loose so shaking is not impeded.

Using water in a drilled hole.

Removing cuttings from deep holes may require more water than is readily available. In this case, small amounts of water may be used to create the mud, and a long-handled spoon can extract it. Oldtime miner's spoons were forged from various lengths of iron rod. They had a handle opposite a flattened, slightly curved end approximately 3/ inches wide and up to 6 inches long. These spoons were used for clearing holes of cuttings and for retrieving sticks of powder from misfired holes. The pointed tip on the handle end was used to thoroughly clean holes before loading and to pack explosives in the holes. Today similar soft metal "powder spoons", made of 3/8-inch iron rod in lengths up to 8 feet, are sometimes still used in underground mines. We made a 30-inch long version of the "powder spoon" for trail work. We also made a spoon from a piece of aluminum tubing 1/2-inch in diameter and about 22 inches long. We flattened and shaped one end so it had a flat edge roughly perpendicular to the rod handle. This spoon worked well for cleaning 1'/-inch holes up to 16 inches deep.

The aluminum spoon we made had a 22 inch
handle and a 5/8 inch spoon.

6. Carefully select the points at which holes will be placed. Use natural points of weakness, and keep in mind your total breaking needs for the project. Evaluate the site and proceed accordingly. If you plan to remove a rock entirely, position the holes as perpendicular as possible to the largest face parallel to its strata (see A below). If the rock is to remain in place with only parts removed, a different technique is used (see B below).

A. Drilled holes are perpendicular to the surface being worked. If wedge and feathers are used in this instance they will be less likely to be unduly stressed, because the compression forces of the rock are more evenly distributed on them. This rock will probably be split into chunks that will allow its complete removal. Arrows indicate probable direction of splitting.

B. The drilled hole is not perpendicular to the surface being worked. Splitting will be both less predictable and less efficient in this situation. Be aware also that when you work the wedge into the hole it will be more prone to bending or breaking because the compression forces are distributed unevenly. You have already determined that only a section of the rock will be removed. That is what you can expect to happen here. Arrows indicate probable direction of splitting.

The same principles can be applied if a prospective trail tread crosses a rock face.

A. If the rock looks and feels solid, drill to remove it completely.

B. If the rock is weathered, seamy, or soft, perhaps you can chip it flat.