April 8, 2025
Many of our hand-held diamond core drilling motors, such as DM6, DMC6, DMC160, DM8, DM62, and DD160, have a recommendation to not use first gear hand-held. The reason for this is simply that the torque generated by first gear is too high for the average person to safely hold, and so must be used on a drillstand.
Gearing can be boiled down to an inverse relationship of rotational speed vs. torque. The lower the speed, the higher the torque, and vice versa. Newton’s third law states that for every action, there is an equal and opposite reaction. When drilling hand-held, the operator needs to counteract the torque generated by the motor with his hands, and in 1st gear, this torque is too high.
New operators may falsely assume that since 1st gear is turning slower, it will be less intimidating. This couldn’t be further from the truth! Actually, 3rd gear is the most manageable with the lowest torque output, and 1st gear is the most dangerous with the highest torque.
You may ask why we would create a hand-held machine that cannot be used hand-held in first gear? The reason is that the total capability envelope of the tool includes rig-mounted operation. The DM6, DMC6, and DMC160, for example, are rated for Ø162mm wet. To achieve that capacity, the rotational speed and required torque dictate the ratio of its first gear, and this torque output is outside of the range of hand-held operation.
These tools are designed for versatility, covering a range of possibilities. For example, their 3rd gear is fast enough for efficient wet drilling in small diameters, while 2nd gear can drill wet up to about Ø92mm. In this range, it is completely manageable to operate hand-held. But when wet drilling in diameters above this, a drillstand is absolutely required.
This versatility extends to their capability of dry drilling in brick materials. Since dry drilling requires a much higher linear speed and is normally performed hand-held, the speeds of 3rd and 2nd gears can comfortably cover the full range of operation, and so 1st gear is not required for dry drilling of brick with these tools.
Always follow the recommended gear selection criteria for safety and best results.