In hammer drilling, the hammer drill’s performance is crucial to the success of the drilling operation. To keep it in good working order, MOTOREX has collaborated with the drilling specialists AG to develop the high-resilience hammer drill oil ROTAC 220. Andreas Bernhard (CEO) answers interesting questions on the topic of hammer drilling.

When precise tunnelling is needed, horizontal drilling machines with hammer drill heads rise to the task with the utmost efficiency. Typical use cases include the laying of cables and pipes beneath built-up areas such as streets or natural obstacles. Andreas Bernhard, CEO of AG, has been familiar with the challenges of microtunnelling for many years.


In hammer drilling, the pneumatically powered hammer mechanism strikes against the rotating drill head (metal on metal). To facilitate this, all moving parts of the hammer mechanism are lubricated and cooled with hammer drill oil to which compressed air is added. Especially when drilling into rock, the pressure and temperature loads are very high. This requires a hammer drill oil with extremely good adhesion and high-pressure stability.

Andreas Bernhard, what pressure do the pneumatic components in a hammer drill mechanism operate at?

“Depending on the situation, we operate at pressures between 13 and 20 bar. The pressure is one big factor and the volume of air is the other. It’s not uncommon for us to run up to six compressors producing approximately 20 m3 of compressed air each (120 m3 in total) in direct proximity to the borehole. The drive and propulsion of the drilling unit are hydraulic and mechanical.”

What distinguishes MOTOREX ROTAC 220 in practice?

“The lubricant is ‘tailor-made’ for hammer drilling. Due to the high viscosity of ISO VG 220, its behaviour is ideal across the entire temperature range and it forms a highly resilient lubricating film. An important factor is the absorption of moisture. In certain use cases (e.g. drilling through rock), we deliberately add water to the compressed air to cool the hammer drill more effectively and to wash away dust. MOTOREX ROTAC 220 absorbs this water and dissipates it in thickened form. We are also impressed by these qualities of the ROTAC 220 mineral hammer drill oil:

  • perfect lubrication and adhesion,
  • no troublesome oil mist formation,
  • excellent wear and corrosion protection,
  • no residue or resin formation
  • and good quality and performance for the price.”

Does ROTAC 220 also protect the hammer drill while it is not in operation?

“Yes and this is an important point. Our equipment has to be ready to deploy within 48 hours. Between deployments, it is out of operation for different periods of time. We have always been able to perform our service and have never had problems with functionality due to corrosion or oxidation of the hammer drill. Evidence of this is also visible when dismantling the drill heads.”

How does the cost of the hammer drill oil weigh up against the value of the hammer drill?

“Our machinery fleet has the most diverse range of hammer drills possible with diameters ranging from 10 to 120 cm. Compared to the value of the hammer drills, the cost of the hammer drill oil is negligible in our calculations. However, from the perspective of maintaining the functionality of the hammer drills, the hammer drill oil is highly valuable. A defective or stiff hammer drill will not only cost a lot of money but also cause unnecessary aggravation. That's why we value MOTOREX lubricants so highly.”

Any closing remarks?

“If you want a successful drilling operation, choosing the right hammer drill oil is everything. Our collaboration with MOTOREX was very professional from our perspective and focused on finding the right solutions.”

MOTOREX ROTAC hammer drill oils are available in a range of viscosity levels and formulations (including biodegradable). They are designed to be used in hammer drills and breaker hammers, pneumatic tools and engines, such as those used in construction and industry. The right drill head is needed for the job. Hammer drilling is the most efficient method of drilling into rock. This presents the hammer drill oil with challenges in a wide variety of disciplines.