Technical Guide · Drilling Tools

DTH Hammer and Drill Bit Selection: Match Tools to Your Rock

By Windrilling Technical Team · August 2026 · 8 min read

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A few years back I stood on a granite quarry bench and watched a crew lose a week to a pairing problem. The rig was sound. The hammer was new. But the compressor feeding that five-inch hammer was simply too small. Penetration dropped to a crawl. Two rods stuck. By Friday the hole was still unfinished, and everyone had learned the hard way what the spec sheet could have told them on day one.

The hammer was never the problem. The match was.

I have watched this same mistake repeat on water wells, road cuts and mine sites across three continents. Most buyers pick a hammer by habit instead of by spec. This guide is the short version of what I tell those crews: the five decisions that get DTH hammers and drill bits right the first time, and the mistakes that quietly eat your meterage.

1. Start With the Rock, Not the Hammer

Rock hardness comes first because it decides two things: the carbide grade of your bit and the impact energy your hammer must deliver. Granite, basalt and quartzite punish cheap bits fast. For that ground I recommend button bits with tougher carbide, driven by a hammer with real blow energy — which usually means a high-pressure hammer, fed properly.

Limestone, sandstone and weathered formations are more forgiving. You can open up the gauge, push rotation speed and stretch wear life. The order matters: choose the bit for the rock, then the hammer that drives that bit, then the air that drives the hammer. Most crews work the list backwards and pay for it in penetration.

2. Match the Bit to Hole Size and Casing

Hole diameter decides bit gauge. Hammer size decides the hole range your rig can hold. On our ZJ516 crawler rig, customers run 90–145 mm holes with 3″, 4″ or 5″ hammers. Step up to a bigger integrated machine like the D452C and you can hold 200 mm holes with an on-board air system and a six-plus-one rod carousel.

If you case the hole, the bit must clear the casing shoe. In broken or cavey ground, a retrac bit lets you pull back without wedging — a small extra cost that saves a long afternoon. The full range of DTH hammers, drill bits and rods is on our tools page, matched to the rigs we ship.

3. Air Is the Hammer’s Fuel — Match CFM and PSI

Every hammer size has a rated air demand. Underfeed it and penetration falls, the string starts to stick, and you burn fuel for nothing. Overfeed it and you are paying for air you never used. My rule: take the hammer spec, then add 15–20 percent reserve for wet ground, worn seals and leaking hoses.

The numbers matter. A machine like the D452C carries an integrated air system delivering 15 m³/min at up to 18 bar — a true one-rig setup for large-hole work. On the compact side, we pair the ZJ516 with a towed compressor matched to the hammer you actually run. Tell us your compressor output and we will tell you which hammer will not choke on it.

4. Drill Rods, Threads and Shank Adapters

Rods are the part everyone forgets until something bends. Diameter matters: 76 mm rods suit smaller holes, while 89 mm rods add the stiffness you want for deeper or larger work. Thread type has to match the hammer and bit system — API regular threads are the common standard, but many hammers use special threads, and that is exactly where a shank adapter earns its keep.

A worn rod is a hidden deviation problem. A bent rod is a stuck string waiting to happen. When you order, confirm rod length, thread and shank together. Mismatched threads in the field are a two-day headache nobody budgets for.

5. Three Field Mistakes That Cost You Meterage

First: mismatched air. A big hammer on a small compressor drills slowly, sticks easily and wears the bit unevenly — the quarry story at the top of this page is that mistake in its purest form. Second: the wrong bit for the formation. Hard-rock button bits in clay will plug. Soft-formation bits in granite will shave away in hours. Third: ignoring wear limits. A bit with a dull gauge reams instead of cutting, and you pay for it in re-drilling. Check gauge wear after every shift. It takes thirty seconds and saves a day.

6. Quick Selection Table

Rock Type	Typical Hole	Hammer Size	Bit Style
Granite, basalt, quartzite	110–150 mm	4″ high-pressure	Button, drop-center
Limestone, sandstone	130–200 mm	5″	Button, flat face
Weathered, mixed ground	90–130 mm	3″	Button, retrac
Cased or cavey holes	100–160 mm	3–4″	Retrac or cross

These are starting points, not rules. The final match depends on your compressor output and site conditions.

7. Checklist Before You Order

• Confirm hole diameter and the casing plan before you pick a bit.
• Match the hammer to your compressor output — with reserve.
• Check rod size, thread and shank adapter compatibility together.
• Ask where wear parts are stocked. Bits, hammers and drill pipes are the consumables you reorder every season.
• Consider the full package. Rig, compressor, tools and spares shipped together is how most of our customers buy, and it is the fastest way to get drilling. See our complete rig packages.

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FAQ

Can I run a 5-inch hammer with a small compressor?

Physically, yes. Practically, no. An underfed hammer drills slowly, sticks easily and wears the bit unevenly. Match the hammer to your real air output, or drop a size — your meterage will thank you.

How long should a DTH drill bit last?

That depends mostly on rock and rotation speed. In hard granite, expect measurable gauge wear in days, not weeks — that is the signal to dress or replace. Track cost per meter and you will know exactly when a bit has paid for itself.

Do you supply hammers, bits and rods with the rig?

Yes. We match hammers, bits, drill rods and compressors to the rig as a complete package. Tell us your rock type, hole size and target depth, and we will send a full package quote within 24 hours.