Direct answer: before using a jackleg or air-leg rock drill underground, the crew should confirm that the ground has been examined and released under the mine’s ground-control procedure, the work area and escape path are clear, the drill/air leg/steel/hoses are serviceable, and the operator can work from a stable position outside foreseeable fall, pinch and hose-movement paths. The crew plan—solo operator, trained helper or dedicated spotter—must also be authorized under the site procedure and applicable working-alone rules. If ground condition, support status, drill restraint, operator position or crew authorization is uncertain, do not start—or stop, isolate the air and escalate to the responsible supervisor.
This guide owns the pre-use go/no-go decision for underground jackleg drilling. It does not design ground support, replace a mine risk assessment or safe-work procedure, prescribe a blast pattern, select a compressor, or choose between rock-drill models. Those adjacent decisions remain with the mine’s competent persons, the equipment manual and the applicable law.
NIOSH research on underground metal mines identified ground-fall exposure at the face, particularly during initial support work, as a central jackleg-drill injury problem. That means a technically healthy drill is not enough: the first decision is whether the place and the task are safe to enter and perform.
Use a go/no-go sequence, not a generic walk-around
A useful pre-use check follows the order in which risk can defeat the job. Start with authority and ground conditions; then check the work envelope; then inspect the complete drilling system; only after those gates pass should the crew connect, pressurize and conduct the controlled functional check.
| Gate | Evidence to confirm | Go condition | No-go / escalation condition |
|---|---|---|---|
| 1. Work authorization | Current work instruction, area status, required permits and named supervisor | Task and area are released under the site procedure | Release is missing, expired, unclear or conditions have changed |
| 2. Ground condition | Examination by the person authorized under the ground-control plan | Ground is supported or otherwise declared suitable for the planned work | Loose ground, new cracking, movement, falls, water change or uncertain support status |
| 3. Working envelope | Stable footing, clear access/egress, drill and air-leg travel, steel path and hose route | Operator and helper can work without entering a fall, pinch or line-of-fire path | Congestion, unstable footing, blocked egress or unavoidable exposure |
| 4. Crew plan | Working-alone rule, communication/attendance method, named roles and exclusion zones | Solo, helper or spotter arrangement is authorized and each person knows the stop and isolation signals | Rule is unclear, contact cannot be maintained, help is unavailable or a person must enter a live movement path |
| 5. Equipment condition | Drill, leg, steel, bit, retainer, controls, oiler, hose, couplings and restraints | Correct components are identifiable, intact and correctly assembled | Damage, looseness, mismatch, missing restraint or uncertain rating |
| 6. Controlled start | Isolation control, people clear, gradual pressurization and short functional check | Controls respond normally; no leak, unexpected motion or abnormal sound | Uncontrolled movement, leak, binding, abnormal vibration or failed control |
1. Confirm the face is released before equipment checks begin
The operator should not turn an equipment inspection into an informal ground-support decision. Confirm who is authorized to examine and release the face, what record or marking shows its status, and whether the release still applies after blasting, scaling, support installation, a seismic event, water change or other disturbance.
An MSHA fatality alert involving a jackleg drill illustrates the boundary. The driller was working near the face and was struck by rock from the roof after attempting to retrieve a detached bit. MSHA’s listed practices include examining and testing ground conditions before work and as conditions warrant, installing support before other work when ground is hazardous, remaining alert to changes and scaling from a location that does not expose people to falling material.
The operating decision is therefore simple even when the geology is not: no tool problem, lost bit or production delay authorizes entry beneath questionable ground. Isolate the task and use the mine’s ground-control and recovery procedure.
2. Build the operator position around stable footing and an exit path
Before moving the drill into position, stand where the operator and helper would stand. Check floor condition, loose material, pooled water, rails, services, drill steels and hoses. Older U.S. Bureau of Mines injury analysis identified slips, trips and falls associated with poor housekeeping around jackleg work, including loose rock, drill steel, hoses and other material underfoot.
The acceptable position should let the operator control the drill without:
- standing beneath loose or unexamined ground;
- straddling or stepping over the air hose, water hose or drill steel;
- placing a body part between the drill/leg and a wall, rib or fixed service;
- standing directly behind a connection or in the likely path of a released hose;
- blocking the helper’s movement or the crew’s route away from the face;
- stretching so far that normal control of the feed and rotation is lost.
Do not use the air leg to force a drill into a position the equipment or operator cannot control. The pusher leg must be the approved match for the drill and must have a stable footing through the intended travel. For geometry and package planning, use the separate narrow-tunnel air-leg setup guide.
Solo operator, helper or spotter: authorize the crew plan before setup
There is no universal rule that every jackleg task requires exactly two people, and “routine drilling” does not automatically make solo work acceptable. The controlling decision comes from the applicable law, mine standard, approved safe-work procedure and the hazards of the specific heading and task. U.S. mine-safety case records show that whether a jackleg operator was “working alone” has been a real enforcement question, while accident guidance emphasizes communication and prompt assistance where hazardous conditions can endanger a person.
Make the crew decision before equipment is moved to the face. A second person is not a control if that person has no defined role, cannot communicate with the operator or must stand in the drill-steel, hose, air-leg or loose-ground exposure zone.
| Planned arrangement | Minimum authorization evidence | Role boundary during live drilling | Hold or escalate when |
|---|---|---|---|
| Solo operation may be considered | The jurisdiction and mine procedure permit it; the operator is task-competent; the area is released; the required sight, sound, check-in or communication method is working; emergency response is defined. | The operator performs only the approved routine task and stops before any handling, recovery or adjustment that the procedure assigns to two people. | The operator cannot be seen, heard or contacted as required; conditions change; assistance cannot arrive within the site-defined response; or the task leaves the approved solo envelope. |
| Trained helper / second worker | A site rule or task assessment requires two people, or isolated setup stages need shared handling under an approved method. | The helper may stage steel, manage services or assist positioning only as the procedure defines and while the drill is isolated. During pressurization and drilling, the helper stays outside the steel, leg, hose and pinch paths. | The helper would need to brace a live drill, hold rotating steel, stand beneath questionable ground or step across a pressurized hose to complete the task. |
| Dedicated spotter or assessor | The work plan identifies why observation is required—for example, supervised training, a blind approach or a controlled competency check—and defines a clear stop signal. | The spotter observes from a protected position with reliable communication. A spotter does not replace the authorized ground examiner, operator or supervisor. | The spotter loses line of sight or communication, cannot stay outside the movement envelope or is expected to make ground-support decisions outside their authority. |
| No-go / replan or mechanize | No arrangement can keep every person outside foreseeable fall, entanglement, crush and hose-release paths while meeting the site rule. | Do not start. Change the sequence, clear the heading, use approved handling assistance or select a different drilling method under the mine plan. | The only proposed solution is an extra person inside the hazard zone. |
Copy-ready crew authorization record
- heading, task, shift and current ground-release reference;
- controlling jurisdiction, mine standard and safe-work procedure revision;
- crew arrangement: SOLO / TRAINED HELPER / SPOTTER / NO-GO;
- operator and helper/spotter competency status;
- required sight, sound, check-in or communication method and test result;
- isolated stages where another person may handle steel, hose or the drill package;
- live-drilling positions and exclusion zones for every person;
- stop signal, isolation owner, emergency contact and response method;
- supervisor authorization and time; and
- conditions that cancel the authorization and require a new review.
Stop boundary: crew size cannot compensate for unreleased ground, an unstable footing, a defective drilling package or an impossible working envelope. If a second person would have to enter the hazard to make the setup function, the correct decision is NO-GO.
Air-leg footing stability gate: external slip or internal leg creep?
“The leg slips” can describe two different failures. External footing slip means the foot, prongs, drill ladder or other approved support moves relative to the floor. Internal leg creep means the foot remains planted but the leg changes length, loses thrust or retracts because of a control, seal, cylinder or pressure fault. Separate these observations before changing parts or increasing feed.
| Observed condition | Evidence to check | Pre-use decision |
|---|---|---|
| Stable floor or approved support | The full intended foot/prong contact is supported; the support does not rock; hoses and steel are clear; the leg has usable travel for the planned collar | PROCEED TO CONTROLLED START under the site procedure |
| Loose muck, rolling stone, broken timber, pooled water, slurry, oil, or a foot bearing on a hose, service, edge or gap | The contact can shift, settle or eject material when thrust is applied | REPOSITION OR CLEAN; do not use added leg pressure to create grip |
| Foot or approved support moves during the controlled start | A witness mark or direct observation shows floor-relative movement; the drill axis also shifts or the operator must catch the machine | STOP AND RESET; isolate, restore a site-approved support condition and repeat the check |
| Foot remains fixed but leg shortens, extends or loses thrust | No floor-relative movement, yet leg length or feed changes | HOLD THE AIR LEG for fault isolation; use the air-leg troubleshooting guide |
| Improvised block, damaged drill ladder, unsecured support or unapproved extension is required | The setup is not covered by the equipment manual and site procedure | NO-GO until the approved support or extension method is available |
| Leg reaches the end of useful travel before the collar is established | The drill cannot maintain alignment and support through the intended movement | REPOSITION; do not continue with side load or an exhausted stroke |
Controlled footing and line-of-thrust check
- Isolate before placement. Clear loose material, hoses, drill steels and trip hazards from the intended foot and operator area. Do not place the foot on a hose, pipe, rail, unsupported edge or loose wedge.
- Use only the approved support method. Where the site procedure calls for a drill ladder, rack, extension or other fixture, verify that it is identified, intact, secured and positioned as designed. Do not improvise with loose rock, scrap steel or damaged timber.
- Check thrust geometry and travel. Position the leg so its thrust supports the drill along the intended hole direction without forcing the drill sideways, trapping the operator or blocking the exit path. Confirm usable leg travel remains for collaring and the planned hole position.
- Conduct a low-energy controlled check. Keep helpers and observers outside the drill, steel, leg and hose movement paths. Apply only the staged start permitted by the equipment manual and site procedure while watching the foot/support, leg length and drill axis as separate references.
- Classify the first movement. Floor-relative foot movement requires a setup correction; leg-length change with a stationary foot requires equipment diagnosis; movement of both means both conditions must be resolved. Stop rather than compensating with more pressure.
- Recheck after change. Repeat the footing gate when the hole position changes, loose material accumulates, water appears, a support moves, the leg is extended differently or the crew loses a clear view of the contact.
Minimum record: note the floor/support condition, support method, planned hole direction, available leg travel, whether the foot moved, whether leg length changed, and the final disposition: PROCEED, REPOSITION, HOLD AIR LEG or NO-GO. These observations turn “the jackleg slips” into evidence that maintenance and supervision can act on.
This gate does not certify ground support or prescribe one universal leg angle. Ground release, support design, approved fixtures, operating pressure and working position remain controlled by the mine procedure and the exact equipment manual.
3. Inspect the complete drill package while isolated
Inspection should cover the connected system, not just the drill body. Isolate the air supply and verify the line is depressurized according to the site procedure before touching couplings, controls or the retainer.
Rock drill and controls
- Confirm the exact drill model and the approved operating manual are available.
- Check the body, backhead, side bolts, handles and control lever for damage, looseness or missing parts.
- Verify controls return and move as designed while the system is isolated; do not free a sticking control with pressure applied.
- Inspect the chuck, retainer and shank area for damage or excessive looseness.
Air leg, drill steel and bit
- Confirm the air leg is the approved model/suffix and its attachment is secure.
- Inspect the leg tube, foot, controls and hose for damage, binding or leakage evidence.
- Check that the foot can bear on a stable surface without slipping into loose material.
- Reject bent, cracked, mushroomed or otherwise damaged drill steel under the site/OEM limits.
- Confirm the shank, bit connection and bit are compatible and retained correctly.
Air, water and lubrication
- Inspect hoses for cuts, abrasion, blistering, soft spots, exposed reinforcement or unidentifiable ratings.
- Check fittings, clamps/crimps, coupling locks, gaskets and required restraints.
- Route hoses so drill movement cannot crush, sharply bend or pull them across the crew’s feet.
- Verify the lubricator has the correct oil, orientation and condition for the selected drill.
- If wet drilling is used, confirm the water connection, shutoff and flushing path under the drill manual and site procedure.
For detailed connection control, use the dedicated hose-restraint and isolation guide. For the line oiler, use the pneumatic rock drill lubrication guide. This page does not repeat those engineering decisions; it verifies that the approved assembly is present and serviceable before work.
4. Conduct a controlled start with everyone clear
- Reconfirm the work area and escape path have not changed during setup.
- Position the drill and leg in the approved start position with the controls in their required state.
- Keep the helper and observers outside the drill-steel, hose and pusher-leg movement paths.
- Open the supply using the site’s controlled pressurization sequence; do not stand over a coupling.
- Check for leakage and unexpected movement without placing a hand on a pressurized joint.
- Perform only the short functional check permitted by the manufacturer and site procedure.
- Stop immediately if a control fails to respond normally, the leg slips, a connection moves, or the drill produces an unexplained change.
A no-load run cannot prove that the ground, operator position or drilling system is safe under production load. It only verifies limited control response. The crew must continue observing ground, footing, hose routing, drill behavior and people movement throughout the task.
Stop-work conditions during drilling
Stop percussion/rotation, isolate the air as required and withdraw to the approved safe position when any of the following occurs:
- rock falls, new cracks, movement, unusual sounds, support damage or another change in ground condition;
- the bit detaches, steel sticks or a component must be recovered from an exposed area;
- the operator loses stable footing or the air-leg foot begins to move;
- a hose, coupling, restraint, clamp or fitting shifts, leaks or is damaged;
- a control sticks, the drill starts unexpectedly, or isolation cannot be confirmed;
- the steel bends, whips, binds or runs out of the planned line;
- water, dust, ventilation or visibility changes so the task can no longer be controlled;
- another person or machine enters the working envelope;
- the operator is unsure whether continuing is permitted.
Do not solve a stop-work condition by increasing feed, air pressure or force. The correct next step is determined by the responsible ground-control, maintenance or operational authority.
Shift record: the minimum evidence worth keeping
| Record field | Why it matters |
|---|---|
| Date, shift, heading and task | Links the check to the actual place and work |
| Ground examination/release reference | Separates equipment inspection from ground-control authority |
| Drill, air-leg and hose asset IDs | Supports defect history and prevents uncontrolled substitution |
| Steel/bit configuration | Confirms the inspected drilling assembly |
| Defects found and isolation status | Prevents rejected equipment returning to service without review |
| Changes during the task | Shows why the work stopped or required re-examination |
| Operator and supervisor sign-off | Identifies who completed and accepted the check under the site system |
Common mistakes
- Starting with the drill instead of the ground: a perfect tool does not make an unreleased face safe.
- Treating a previous shift’s release as permanent: blasting, scaling, water and other changes can alter conditions.
- Combining every safety topic into one tick box: ground, equipment, connections and exposure each need a responsible decision.
- Retrieving a lost bit immediately: recovery must not put a person beneath questionable ground.
- Accepting a hose restraint as proof of a good coupling: the hose, fitting, lock, rating and restraint all have separate functions.
- Using the pre-use check as an equipment-selection guide: model, air demand and compatibility belong to the procurement and setup process.
RFQ block for a jackleg drilling package
When requesting an air-leg rock drill package, provide:
- underground application, heading dimensions and drilling direction;
- hole diameter, typical depth, rock and water conditions;
- required drill and air-leg model/suffix or current equipment identification;
- drill-steel shank, length, bit connection and bit diameter;
- compressor conditions, hose inside diameter/length and connection standard;
- water-flushing and lubrication arrangement;
- site-required coupling locks, hose restraints and isolation devices;
- requested spare kit, manuals, inspection evidence and destination.
Review the current PerfoMax pneumatic rock drill range, then send the operating inputs and photos through the RFQ page. PerfoMax can help confirm the equipment and connection package; the mine remains responsible for ground control, work authorization, training and the site procedure.
Frequently asked questions
What is the first check before using a jackleg drill underground?
Confirm the work area has been examined and released under the mine’s ground-control procedure. Equipment checks do not replace that authorization.
When should jackleg drilling stop because of ground conditions?
Stop and withdraw to the approved safe position when ground moves, falls, cracks, sounds different, support is damaged, water conditions change or the crew is uncertain. The responsible competent person must determine the next action.
Can the operator recover a detached bit from the face?
Only under the mine’s approved recovery and ground-control procedure. A lost tool does not justify entering an exposed area or working beneath questionable ground.
Does a pre-use checklist replace the equipment manual?
No. It organizes the go/no-go decision. Component limits, assembly, operation, isolation and maintenance must follow the exact manual and site procedure.
What information should be recorded after a failed pre-use check?
Record the location, equipment asset IDs, defect or changed condition, isolation/tag status, person notified and release or repair required before return to service.
Technical references
- NIOSH — Jackleg Drill Injuries (peer-reviewed, 2016)
- MSHA — Jackleg-drill fall-of-ground fatality alert and best practices
- U.S. Bureau of Mines — Analysis of Injuries Involving Jackleg Rock Drills
- OSHA — Power-operated hand tools, pneumatic-tool requirements
- Federal Mine Safety and Health Review Commission — jackleg drilling and working-alone decision record (2017)
This article is a procurement and pre-use decision aid. It does not replace the mine’s ground-control plan, approved safe-work procedure, training, supervision, equipment manual or applicable law.