Tips for Efficient Drilling
How to run a top hammer rock drill the way the tool was engineered to run: square to the hole, steady on the feed, fed clean air and clean oil, with a clean hole under the bit. Get these habits right and the same drill cuts faster, the steel lasts longer, and the bit bill drops.
The Five Habits
- Stay aligned – collar square, drill square.
- Hold steady feed – never let the drill bounce.
- Deliver 90 psi at the tool, not the compressor.
- Keep the hole blown clean, every rod.
- Oil the drill, grease every thread.
A pneumatic rock drill does not push a bit through rock – it launches a stress wave down the steel roughly 2,000 to 4,000 times a minute, and the carbide crushes a few millimeters of rock with each blow. Everything on this page serves that one physical fact. Misalignment scatters the wave. A bouncing drill sends it through threads that were never meant to carry it. Low air starves it. A dirty hole makes the bit re-crush its own cuttings. Dry threads and dry shanks turn it into heat and galled metal.
What this page is – and is not
This is a technique and care guide for people already running a drill. If you are still choosing equipment, use our buyer’s guides: Choosing a Rock Drill and Choosing Drill Steel and Rock Drill Bits.
Get the Drill, Steel, and Bits Ready
Most “drill problems” are set-up problems. A worn chuck bushing, a beveled striking face, or a chipped shank will ruin new components in hours – the piston strikes wrong, the shank mushrooms, and the damage cascades down the string. Five minutes of inspection prevents nearly all of it.
Protect the carbide before it ever cuts rock. Tungsten carbide is harder than anything on the jobsite except other carbide – which is exactly why bits chip when they clatter against each other in a bucket. Keep bits in their containers, under cover, and clean. Rack drill steel on wooden planks or horses, off the ground, with threads protected.
Prove the oiler before you collar. Start the drill at low throttle and confirm lubrication is actually reaching the tool – the shank should come out of the chuck wet with oil. A dry shank galls in the bushing, batters the collar, and mushrooms. (Full lubrication drill-down in Phase 7.)
60-Second Pre-Drill Checklist
- Operator knows this drill and safe drilling practice
- Striking face square and true – not beveled, worn, or chipped
- Chuck bushing checked for wear and shank fit
- Shank end square, not worn or chipped
- Line oiler filled; low-throttle start shows oil at the shank
- Steel rolled on a flat surface – no visible bow
- Threads inspected: no galling, flattened flanks, or knife edges
- Enough steel, bits, and thread grease on hand for the shift
- Retainer latched; hose whip checks on
Maintain Alignment From the First Inch
The hole is aimed in the first few inches – and so is most of the damage. Position the drill on firm footing before you start. Collar the hole with the drill square to the work, on a tight feed and a low throttle. If you are on a mast, guide shell, or feed leg, make sure it is firmly supported against the ground or the face and the centralizer is closed. Only after the bit has buried itself do you open the throttle and adjust the feed up.
Why it matters: drill steel is a waveguide, not a pry bar. When the string runs at an angle to the hole, the steel flexes on every blow. Misalignment causes stuck steel; broken shanks, couplings, and rods; and accelerated wear on chuck parts and bit gauge. A bent rod then whips in the hole, cutting it oversize and fatiguing toward a break at the thread runout.
Check your steel, not just your stance. Roll each rod on a flat surface at the start of the shift – visible wobble (more than about 0.5 mm of bow per meter) means retire it. A bent rod can never drill a straight hole, no matter how good the operator is.
Do
- ✓Set firm, secure footing before starting
- ✓Collar at low throttle on tight feed, square to the face
- ✓Support the mast or leg solidly; close the centralizer
- ✓Open the throttle only after the bit is buried
Don’t
- ✗Lean the drill sideways to “steer” a wandering hole
- ✗Collar at full throttle – the bit skates and the hole starts crooked
- ✗Run bent steel – it whips, oversizes the hole, and breaks
- ✗Side-load one-piece steels; slender bodies bend and pop brazed tips
Down Pressure: Hold the Bit on the Rock
Feed pressure is the single skill that separates operators. The goal is simple to state and takes a shift to learn: keep the bit firmly against the bottom of the hole at all times, with enough feed that the drill pulls smooth and steady – never bouncing, never buried. The drill should sound even; a chattering, slapping drill is telling you the bit is leaving the rock between blows.
Too Little Feed
The drill bounces and the string runs loose. Threads and bits wear prematurely, heat builds in the string, shanks batter – and the drill can start dieseling. Insufficient feed is a form of dry firing: blow energy that should exit into rock is absorbed by the drill’s own internals.
Correct Feed
Bit stays planted on the bottom of the hole. Steady exhaust note, smooth rotation, consistent cuttings flow. Rotation indexes the carbide onto fresh rock each blow, and the joints stay tight so the stress wave passes clean to the bit.
Too Much Feed
The steel buckles and binds in the hole, rotation stalls, and couplings jam so tight they will not break loose. In hard rock, over-feeding actually slows penetration. In soft rock, it buries the bit and hangs the steel.
Read the rock and adjust both controls together. Penetration is slower in hard rock, so reduce feed accordingly – the bit needs time to do its work. In soft ground, ease off the feed too, and remember to throttle the hammer down with it; full power into soft material just buries the bit.
Field Note – Never Let a Shoulder-Drive Drill Bounce
On standard US contractor steel (H thread), the bit seats against a forged shoulder, and that shoulder – not the threads – carries the blow. The short threads only hold the bit on. If the drill bounces and the skirt unseats from the shoulder, every blow passes through those small threads, and they strip in short order. Constant down pressure is not a style preference on shoulder-drive tooling; it is how the joint is engineered to survive.
Field Note – Dieseling Will Destroy a Hammer
Dieseling is drill oil igniting inside the tool. It happens when the drill runs with insufficient feed pressure, or at full throttle while you withdraw the bit. The burn overheats the drill and strips its lubricant film – the result can be a destroyed hammer. If you hear it, slow the throttle and increase feed pressure immediately, and throttle down before pulling steel.
Air Pressure: 90 psi at the Tool, Not the Compressor
Every pneumatic drill in our line is rated at 90 psi (6.2 bar) measured at the tool inlet. That number is where the design lives: below it, the drill simply slows; push much above it (roughly 100-102 psi maximum on most handheld drills) and the tool runs rough and wears out fast. Air pressure and feed pressure are linked – if supply pressure is low, you cannot hold sufficient feed, the string runs loose, threads and bits wear prematurely, and heat builds in the string.
The hose is where power disappears. Undersized or overlong hose can drop 100 psi at the compressor to 70 psi at the drill – roughly a 30 percent power loss you will blame on the drill, the bit, or the rock. Good system design keeps total pressure drop to 10-15 psi: correct hose diameter for the drill’s CFM draw, the shortest practical run, and fittings that do not choke the line. Drain water from lines and hoses before connecting, and blow the hose clear before coupling it to the tool.
Sizing a compressor for your drill class? That is a buying decision – see Choosing a Rock Drill for consumption and pairing tables, and shop air compressors.
| Air at the Tool | Impact Rate | Energy per Blow | What You Feel |
|---|---|---|---|
| 80 psi | 2,256 BPM | 59.6 ft-lb | Drill feels lazy; penetration drags |
| 90 psi | 2,302 BPM | 69.2 ft-lb | Rated performance |
| 100 psi | 2,418 BPM | 84.8 ft-lb | Fast – and near most tools’ limit |
Manufacturer performance curve for a 60 lb class jackleg drill (BTE Mid-Western S83). The takeaway: a 10 psi shortfall costs roughly 15 percent of blow energy.
Keep the Hole Clean
The bit can only break rock it can reach. Flushing air (or water, on wet drills) travels down the hollow bore of the steel and out ports in the bit face, lifting cuttings up the annulus around the rod. When flushing falls behind penetration, the bit re-crushes its own cuttings – wear accelerates dramatically, penetration collapses, and the string packs in and sticks.
Blow the hole frequently in deep drilling. In soft ground or where water seeps in, a mud collar can form around the steel and hang up the string. Make it a rule: blow the hole every time you add a rod. The habit costs seconds, and it doubles as a diagnostic – if the blow does not clear the hole, you have found a plugged steel before it found you.
If return air or water stops, stop drilling. No return means cuttings are packing under the face or the bore is plugged. Clear the ports and the bore before another foot – drilling on packed cuttings is how strings get stuck and skirts get split.
Do
- ✓Blow the hole often in deep holes – and with every rod added
- ✓Watch the cuttings flow like a gauge; it should be constant
- ✓Stop and clear the moment return flow dies
- ✓Consider wet drilling in seepy or dusty ground – it suppresses silica dust and cools the bit
Don’t
- ✗Drill through a dying return flow “to finish the rod”
- ✗Let a mud collar build in wet, soft ground
- ✗Ignore a sudden penetration drop – it is often a plugged port, not hard rock
- ✗Run button bits in sticky clay seams that smear faces and plug ports – cross or steel bits handle it better
Chasing Bits: Changing Bits Mid-Hole Without Jamming the String
Every bit cuts a slightly smaller hole as it wears. A 2 in bit worn to 1-7/8 in has been drilling an undergauge hole – and a brand-new, full-gauge bit sent down that hole will jam, get pinched, and break. Freeing it bends rods and splits bit skirts. The fix is a rule old drillers call chasing the bit down:
The Right Way to Chase a Hole
- ✓In longholes, always follow the starter bit with a smaller bit – step the diameter down as the hole deepens, never up.
- ✓If you must run a new bit into an existing hole, ream in gently with the old worn bit first, or start a clean hole.
- ✓Measure across the gauge buttons with calipers each shift – it tells you the true hole size the next bit will meet.
- ✓In collapsing or broken ground, run retrac bits – their rear-facing skirt edges ream the bit back out instead of seizing.
How Strings Get Stuck
- ✗New full-gauge bit forced down a worn, undergauge hole – the classic jam.
- ✗Hammering on a stuck bit with a sledge – split skirts are the signature. Work a stuck string free under power, with rotation and reverse feed.
- ✗Drilling on after a bit breaks. If you cannot flush every particle of steel and carbide out of the hole, abandon the hole – drilling on broken carbide guarantees the next broken bit.
- ✗Letting a cross bit wear square in abrasive rock – it rifles a spiraled hole you may not get the steel back out of. Gauge-grind it round or retire it; an X-face bit avoids rifling in the first place.
Lubricating Your Rock Drill – and Its Threads
1. Rock drill oil, continuously, in the air stream
Pneumatic percussion tools need constant oil in the air; running dry is the fastest way to destroy one. Run a line oiler mounted within about 8-10 ft of hose from the drill (or keep the integral oiler filled, on drills that have one), and refill it roughly every two hours of run time. Use true rock drill oil – it carries EP additives for shock loading, tackifiers to cling to moving parts, and emulsifiers that keep working in a wet air stream. Ordinary motor oil has none of that. Match viscosity to the weather: lighter grades (around ISO VG 32-68) in cold conditions, heavier (up to VG 150-220) in high heat.
The test is the shank: it should come out of the chuck wet with oil, every time. Dry shanks gall in the bushing, batter, and mushroom – and a mushroomed shank ruins the piston next.
2. Thread grease, on every make-up
Every threaded joint – rod to coupling, bit to steel – gets thread grease before make-up. The right product is a copper-based rock drill thread compound: it prevents galling (dry flanks cold-welding under impact), keeps joints tight enough to pass the stress wave yet loose enough to break out by hand, and manufacturer literature credits consistent thread lubrication with extending rod life on the order of 30 percent.
The habit that matters: grease the male thread before every make-up – not once a shift. Keep the grease container covered so dust and grinding grit do not turn your lubricant into lapping compound, and keep shank, coupling, steel, and bit threads clean.
Field Note – The Cheapest Insurance in the Catalog
Dry threads gall; dry shanks mushroom. Both are preventable for under 30 dollars. A gallon of rock drill oil and a tub of thread grease protect a drill string worth a hundred times that – put them on every steel and bit order.
Care and Maintenance of the Drill String
Match, rotate, and keep it tight
Run new bits with new steel whenever possible. A new bit on worn steel develops excessive thread wear fast – and worn bits chew up new steel threads just as quickly. On extension strings, replace rods and couplings as matched sets; a worn coupling eats a new rod’s threads in days.
Rotate sectional steel through the string so thread wear spreads evenly, and turn rods end-for-end to equalize wear between the two thread ends. Keep every joint tight while drilling: threads hold the components together, but they are not designed to transmit hammer energy – the rod ends must butt firmly in the coupling, and the steel must bottom against the bit. Loose joints hammer their own threads to death and bleed energy that should be breaking rock.
Retire threads on schedule, not on hope. Inspect at the start and end of every shift; discard anything with spalled threads, flattened flanks, a knife-edge crest, or damaged rod ends. It is false economy to chase the last ten percent of thread life – the failure it causes costs more than the rod.
Handle it like precision tooling – because it is
Fight corrosion. Mine and tunnel water can be aggressively corrosive, and corrosion pits become fatigue cracks. If rust appears, clean it off thoroughly and coat the steel with protective oil or grease. Store steel dry, racked off the ground, threads protected – a rod left wet in a hole over a weekend is measurably closer to breaking.
No drops, no prying, no hammering. Nicks and dents from dropped or thrown rods start fatigue cracks. Drill steel is not a pry bar, a prop, or a lever. And never beat a rock bit off with a steel hammer – the carbide can shatter, and body nicks split skirts. Use a bit wrench, or rattle bits loose by running the drill at low throttle with no rotation.
Recondition bits on interval. Sharp bits mean more penetration, more production, and longer drill and string life. If couplings run hot or joints jam so tight they will not break, something is wrong upstream – look for dulled bits, worn threads, or excessive feed. And scrap any component showing blue or purple heat discoloration: the heat treatment has been cooked out of it.
Troubleshooting: What the Drill Is Telling You
| Symptom | Likely Cause | Fix |
|---|---|---|
| Penetration falls off gradually | Dull bit – wear flats on buttons or rounded inserts | Inspect the face; replace or recondition the bit. A dull bit spends drill time and air to avoid a bit purchase. |
| Penetration falls off suddenly | Plugged flushing, broken button, or collapsed hole | Stop. Clear ports and bore; inspect the face; ream or fish as needed. |
| New bits jam in existing holes | Previous bit wore undergauge | Chase down a bit size; ream transitions with the old bit; measure gauge each shift. |
| Bit spins loose on the steel | Bouncing – insufficient feed unseating the shoulder | Hold constant feed pressure; inspect bit and steel threads before reusing. |
| Threads gall or seize | Dry make-up; worn parts mixed with new | Thread grease on every make-up; replace rod and coupling as sets. |
| Couplings overheat or jam solid | Dulled bits, worn threads, or excessive feed | Find the upstream cause; do not just muscle the joint apart. |
| Rod breaks at the thread runout | Fatigue – loose joints, bent rod, or corrosion pits | Tighter make-up, roll-check straightness, dry storage; scrap pitted rods. |
| Shank mushrooms; collar cracks | Dry firing, dry shank, or wrong shank for the chuck | Steady feed, verify shank size, keep the oiler filled. |
| Drill runs hot, oil smell, rough note | Dieseling – insufficient feed or full throttle on withdrawal | More feed, less throttle; throttle down before pulling steel. |
| Stuck steel | Collapsing ground, packed cuttings, undergauge transition | Keep flushing ahead of penetration; recover with rotation and reverse feed under power – never a sledge; run retrac bits in bad ground. |
Non-Negotiables: Safety Around the Drill String
Efficiency never outranks these. They come straight from OSHA and MSHA drilling rules and manufacturer operating manuals.
Old Holes Are No-Drill Zones
Never collar in a bootleg (the stub of an old blast hole) and never drill where you could intersect a misfired charge. This is federal law, not advice.
Control Silica Dust
Drilling rock and concrete makes respirable crystalline silica. Use wet drilling or shrouded HEPA dust collection to meet the 50 microgram exposure limit.
Retainers and Whip Checks
Never run without the steel retainer latched. Secure hose couplings with whip checks, and disconnect and bleed the air line before every steel change.
Hands Off the Steel
Never hold or steady the drill steel while collaring, and keep hands off the chuck while drilling. Collar at reduced throttle against the work.
Protect Ears and Hands
Pneumatic drills exceed 110 dB – run plugs plus muffs. Sharp bits vibrate less than dull ones; rotate operators on long drilling shifts.
Efficient Drilling, Answered
How much down pressure should I put on a rock drill?
Enough that the bit stays planted on the bottom of the hole and the drill never bounces – but not so much that the steel buckles, binds, or stalls rotation. Listen for a smooth, even exhaust note. Reduce feed in hard rock (penetration is slower there), and reduce both feed and throttle in soft ground.
What air pressure does a pneumatic rock drill need?
90 psi measured at the tool inlet is the industry rating point; most handheld drills allow about 100-102 psi maximum. The pressure at the compressor does not count – undersized or overlong hose can drop 100 psi at the compressor to 70 psi at the drill. Keep total line loss to 10-15 psi.
Why does my new bit jam in a hole the old bit drilled?
Because the old bit wore undergauge and cut a smaller hole than its nominal size. Follow a starter bit with a smaller bit in longholes, or ream the transition gently with the old bit before sending a new full-gauge bit down.
What is dieseling in a rock drill?
Drill oil igniting inside the tool, usually from running with insufficient feed pressure or holding full throttle while withdrawing the bit. It overheats the drill and burns off its lubricant, and can destroy the hammer. Slow the throttle and increase feed to stop it.
What oil should I use in a rock drill?
Dedicated rock drill oil, fed continuously by a line oiler within about 8-10 ft of the tool and refilled roughly every two hours of run time – lighter grades in cold weather, heavier in heat. Motor oil lacks the tackiness and emulsifiers a wet air stream demands. The shank should always come out of the chuck wet with oil.
How often should I grease drill steel threads?
Every single make-up – rod to coupling and bit to steel – with a copper-based rock drill thread compound, not once a shift. Consistent thread lubrication prevents galling and is credited with extending rod life on the order of 30 percent.
Choosing Equipment? Start With the Buyer’s Guides
This page covers how to run the string you own. These guides cover what to buy in the first place.
Choosing a Rock Drill
Weight classes, sinkers vs. jacklegs, air requirements, and which drill fits your holes.
Buyer’s GuideChoosing Drill Steel & Rock Drill Bits
Shanks, thread systems, cross vs. button bits, and matching the consumables to the drill and the rock.
Buyer’s GuideChoosing a Concrete Breaking Tool
Breakers, chipping hammers, and rivet busters – sized to the job.
Stocked for Every Foot You Drill
Rock drill oil, thread grease, drill steel, bits, couplings, and the drills themselves – with product experts who have heard every symptom on this page.