اختيار مطرقة DTH وقلم الحفر: الحجم والضغط والمطابقة

For hard, abrasive rock such as granite, basalt and quartzite, use a high-pressure DTH hammer rated for 17–24 bar fitted with a tungsten-carbide button bit, and match both to your hole diameter and your compressor's free air delivery. High-pressure hammers deliver more energy per blow and hold up better in hard rock, while low-pressure hammers (7–10 bar) suit soft to medium formations. A hammer is only 'best' when hammer, bit and air supply are matched — mismatching any one of the three is the usual cause of slow penetration and short bit life.

Low-pressure hammers work at roughly 7–10 bar (100–150 psi); high-pressure hammers typically need 17–24 bar (250–350 psi). Raising pressure increases both the impact energy and the blow frequency, which is why hard-rock projects almost always run high-pressure hammers. Always check the hammer's air consumption at your actual working pressure, not at the compressor's rated pressure.

Three things must line up: the bit shank must match the hammer model, the bit diameter must match the hole size with the correct clearance, and the button design must suit the rock. Use spherical buttons for hard, abrasive rock, and ballistic or parabolic buttons for softer or medium formations where faster penetration matters more than wear resistance.

The most common causes are: air volume at the bit falling off (leaks, an undersized compressor, or hole-cleaning velocity too low to lift cuttings), a worn bit with blunt buttons, and cuttings not being cleared from the hole bottom. Check the compressor output at working pressure, confirm the hammer's air consumption, and replace the bit when the buttons are worn flat or the gauge is under size.