Drill Oil Selection: What Actually Goes Down the Hole

Drill oil is the smallest line item on a drilling program budget and one of the biggest levers on hammer life. The wrong oil kills a $12,000 DTH hammer in a week. The right oil keeps it in service for a full season.

Rock drill oil vs standard hydraulic oil

Rock drill oil is a specialty lubricant injected into the air line ahead of a DTH or top hammer. It is not the same as the hydraulic oil in the rig — rock drill oil is engineered for:

• Extreme pressure additives that survive percussive shock loading
• Tackifiers that stay on the piston and bit shank despite high-velocity air
• Water resistance for wet holes and high-humidity air
• Anti-foam agents so the oil does not blow past the piston seals

Running generic 30-weight or hydraulic oil in place of rock drill oil is the fastest way to destroy a hammer.

Injection rate

Manufacturer specs vary, but a common range is 1 to 3 pints per hour of drilling. Cold weather, wet holes, and high-pressure hammers push the injection rate higher. Verify with your hammer manufacturer.

Cold-weather formulations

Standard rock drill oil thickens below about 20°F. In winter operations, switch to a low-pour-point winter formulation or blend with a compatible pour-point depressant. Cold oil that does not reach the piston is the same as no oil.

Bio-based drill oils

Many water well and geothermal programs — especially near potable water sources — require biodegradable drill oils that pass EPA VGP standards. Bio-based rock drill oils are readily available, cost slightly more, and lubricate as well as petroleum-based products when correctly matched to conditions.

What Republic stocks

We carry rock drill oil in 5-gallon pails and 55-gallon drums at all four US hubs, including winter and biodegradable formulations. Order with your bits and hammers and it ships on the same truck.

Browse tooling or call 888-953-7455.