DTH Hammer Lubrication Guide: Rock Drill Oil, Oil Rate, and Wet Drilling

DTH Hammer Lubrication: How to Choose Rock Drill Oil and Set the Oil Rate

Short answer: a DTH hammer should be lubricated continuously with a purpose-formulated pneumatic rock drill oil delivered into the compressed-air stream. The correct feed rate is not determined by hammer diameter alone. It depends on the exact hammer model, actual air volume, lubricant viscosity, ambient temperature, and whether water or foam is injected. Start with the hammer manufacturer's manual, meter oil through an inline lubricator, confirm that oil is reaching the hammer, and increase protection when wet drilling requires it.

This guide is written for quarry, mining, water-well, construction, and drilling-service teams that need a practical way to set up DTH hammer lubrication without relying on generic “drops per minute” rules.

1. Why DTH Hammer Lubrication Is a System Setting, Not Just an Oil Choice

A DTH hammer uses compressed air to drive a reciprocating piston and to carry lubricant through the internal working surfaces. The oil film has to survive repeated impact, sliding contact, heat, contamination, and—in many applications—water injection. Correct lubrication helps limit friction, galling, corrosion, and premature wear. The oil film also helps seal running clearances inside the hammer, so lubrication condition can affect hammer efficiency as well as component life.

That is why two rigs using the same nominal hammer size can require different lubrication settings. If one compressor delivers more air, one job injects water, or one site operates in a much colder climate, the oil delivery requirement can change even when the hammer diameter looks the same.

2. What Oil Should You Use in a DTH Hammer?

Use a high-quality rock drill oil designed for pneumatic percussion tools, unless the exact hammer manufacturer specifies another approved product. Major DTH manufacturers consistently treat rock drill oil as a dedicated lubricant category rather than an interchangeable substitute for engine, hydraulic, or gear oil.

Epiroc, for example, describes its Rock Drill 100 as a lubricant developed for the special requirements of DTH, pneumatic, and hydraulic rock drills, with high oil-film strength under demanding conditions. This is a useful reminder that “oil is oil” is the wrong purchasing assumption for a hammer.

Viscosity: follow the hammer and oil supplier, not a universal temperature chart

Viscosity must remain suitable for the operating temperature and the lubricator. Oil that becomes too thick may be difficult to meter and transport; oil that becomes too thin may not maintain the required film. Exact grade recommendations vary by hammer family and lubricant manufacturer, so use the approved viscosity range in the relevant manual or oil data sheet rather than copying a generic ISO or SAE grade from another hammer.

3. How Much Oil Does a DTH Hammer Need?

There is no universal oil rate that is correct for every DTH hammer. The most defensible starting point is the exact manufacturer's lubrication specification, normally tied to air consumption or hammer model. Air volume matters because the compressed air is the carrier that transports oil through the drill string and hammer.

As one model-specific example, Rockmore's ROK DTH Hammer Operation and Service Guide specifies a minimum of 0.2 L/hour per 3.0 m³/min of air (approximately 1/3 pint/hour per 100 cfm) for the ROK and ROK T families. Treat that figure as a Rockmore manual value—not as a universal PerfoMax or industry setting. Another hammer may specify a different rate.

4. How to Set Up an Inline Lubricator

For continuous drilling, use a metered inline lubrication system sized for the compressor flow and recommended by the rig or hammer supplier. A reliable setup should let the operator see or verify oil consumption rather than simply opening a needle valve by feel.

1. Identify the hammer precisely. Record make, model, nominal class, top-sub connection, and the manual revision used.
2. Check the compressor's real operating point. Note air volume and pressure delivered during drilling.
3. Select an approved rock drill oil. Confirm the viscosity is appropriate for ambient conditions and the lubricator.
4. Fill and inspect the oiler. Make sure the reservoir, lines, and metering mechanism are clean and functional.
5. Prime according to the hammer manual. After a long shutdown or before commissioning, oil may need to be introduced directly into the hammer or air line so the machine does not start dry.
6. Set the initial feed rate from the OEM specification. If the manual gives a flow-based formula, calculate from actual air volume.
7. Run and verify delivery. Confirm that lubricant is reaching the hammer and that consumption matches the target over a known time period.
8. Recheck after changing drilling conditions. Water injection, temperature, compressor settings, or a different hammer can all require a new setting.

A useful operating control is to track oil consumed per hour or per shift. If the reservoir level hardly moves during a high-air-flow shift, the issue may be a blocked line, an incorrectly adjusted lubricator, oil that is too viscous for the conditions, or a metering fault—not simply “low oil demand.”

5. What Changes When You Use Water Injection?

Wet drilling needs special attention because water can interfere with the oil film. Mincon specifically advises increasing oil volume when water injection is used so adequate protection is maintained inside the hammer. The required increase depends on the hammer and the amount and location of water introduction.

Do not apply one universal multiplier to every hammer. Instead:

• confirm the hammer manufacturer's wet-drilling lubrication instruction;
• record the water or foam injection rate;
• check that the lubricator can still meter oil consistently at the selected viscosity;
• inspect the hammer more frequently during the first shifts after a change; and
• treat corrosion, scoring, or rapid wear as evidence that the complete air-water-oil system needs review.

6. Under-Lubrication vs. Over-Lubrication: What Should Operators Look For?

Lubrication problems can resemble other DTH faults, so do not diagnose only from penetration rate. Use several observations together and confirm the hammer's internal condition during scheduled inspection.

Robit's current H-series troubleshooting guidance lists both insufficient and excessive lubrication as possible causes of operating problems and recommends checking oil level and adjusting the lubrication valve. The practical lesson is simple: “more oil” is not a substitute for a measured setting.

7. Five Lubrication Mistakes That Create Avoidable DTH Hammer Cost

1. Choosing oil only by viscosity. A similar viscosity does not prove the product is appropriate for pneumatic percussion service.
2. Setting the oiler by hammer diameter alone. Air consumption and the exact hammer design matter.
3. Keeping the same rate after adding water. Wet drilling can require more lubrication.
4. Starting a dry hammer after a long shutdown. Oil may take time to travel through the air system, so follow the manufacturer's priming procedure.
5. Never measuring consumption. An operator cannot confirm a lubrication target if the team never records how much oil actually passes through the system.

8. A Practical Pre-Shift DTH Lubrication Checklist

• Correct hammer make and model identified.
• Correct rock drill oil and viscosity grade available.
• Lubricator reservoir filled and clean.
• Metering system, hoses, and fittings free from leaks or blockages.
• Compressor flow and pressure appropriate for the hammer.
• Water or foam injection status recorded.
• Lubrication rate set from the correct manual.
• Hammer primed if required after storage or long shutdown.
• Oil delivery verified before sustained full-load drilling.
• Oil consumption logged for the shift.

9. What Information Should You Send When Requesting a DTH Hammer or Lubrication Recommendation?

A supplier cannot responsibly recommend a lubrication setting from “4-inch hammer” or “5-inch hammer” alone. Include the system information that changes the answer:

• hammer brand and exact model;
• nominal hammer class and bit shank;
• top-sub / drill-pipe connection;
• required hole diameter and application;
• compressor air volume and operating pressure;
• water or foam injection rate and injection point;
• ambient temperature range;
• current rock drill oil product and viscosity;
• lubricator type and current hourly consumption;
• photos of piston, cylinder, chuck, shank, and unusual wear if troubleshooting.

For a current PerfoMax DTH system starting point, see the DTH Hammer Selection Guide, the CIR90 4-inch-class DTH Hammer, the CIR110 5-inch-class DTH Hammer, or browse the DTH Tools collection. For a project-specific review, send the operating data above through the Request a Quote page.

FAQ

What kind of oil should I put in a DTH hammer?

Use a purpose-formulated pneumatic rock drill oil that is approved for the hammer and suitable for the operating temperature. Do not assume that engine, hydraulic, or gear oil is interchangeable just because its viscosity looks similar.

How much oil does a DTH hammer need per hour?

Use the exact hammer manufacturer's rate, often expressed relative to air consumption. Do not use one universal number across brands and models. For reference only, Rockmore's ROK manual specifies a minimum of 0.2 L/hour per 3.0 m³/min of air for its ROK and ROK T families.

Should I increase DTH hammer oil when drilling with water?

Usually, wet drilling requires additional attention to lubrication because water can reduce the protective film. Mincon explicitly advises increasing oil volume with water injection. The amount should follow the exact hammer manufacturer's guidance rather than a universal multiplier.

Is an inline lubricator necessary?

For continuous DTH drilling, a metered inline lubrication system is the normal way to deliver rock drill oil through the compressed-air stream. Manual priming may still be required at commissioning, after storage, or after a long shutdown, depending on the hammer manual.

Can too much oil cause problems?

Yes. Excessive lubrication can contribute to poor or erratic operation in some hammer systems, while too little oil accelerates wear. The target is the manufacturer-specified amount delivered consistently—not the maximum possible flow.

Technical References

• Mincon — Extending Hammer Life in Blast-Hole Drilling
• Epiroc — Rock Drill 100
• Rockmore — ROK LT DTH Hammer Operation and Service Guide
• Robit — DTH Hammer Operation and Service Manuals

Next Step: Match Lubrication to the Complete Drilling System

Correct oil is only one part of DTH reliability. The hammer, bit, air supply, drilling fluid, drill string, and lubrication system have to work as one system. If you are selecting or replacing a DTH hammer, send PerfoMax your hole diameter, formation, compressor capacity, connection details, water/foam setup, and current lubrication method. That information makes it possible to check compatibility before quotation instead of correcting mismatches in the field.