Rock bolts are one of the support systems, that are widely used support systems in mining and various civil engineering operations. Rock bolts or anchors play a very important role as systematic support during the excavation stage of tunneling or mining work, the bolts can go into the roof of underground mines or the walls of tunnels to prevent caving. The anchor bolts reinforce the loose and weak strata to make them, self-supportive by enhancing their inherent strength. Anchoring of the rock bolt plays an important role when the deformation or movement of the layers in the rock mass induces axial tensile load in the installed rock bolts. Their purpose is to improve the resistance of the ground. Bolts will fail if the applied or induced axial load to the bolt exceeds the anchorage strength. Anchorage strength depends on many factors such as type of bolt, annular space, grouting media, shear behavior at the bolt-grout interface, surface profile, installation mechanism and position. The stability of structures in any tunneling and mining excavation is critical and roof rock stability has long been the primary concern in all underground excavations. Rock bolting has been successfully utilized worldwide for excavation support and slope stabilization and its use continues to grow rapidly. A single use drill bit, selected to suit the ground condition, is fitted to the leading end of the hollow bar ( also called Self-Drilling Anchors)with an anchor plate and anchor nut fitted on the trailing end. Couplings can be used to combine hollow bar sections for extension bolting. What are purposes of Rock bolts installed? 1. Provide pre-tension in fragile geology conditions;2. Serves as a mortar bolt for passive loading. For the pre-tension purpose, immediate anchoring of rock bolts with loose rock geology is necessary. Rock bolting carries the tension and shear forces to prevent the displacements of rock mass, There are three kinds of anchoring material to fulfill the pre-tension purpose within 2-3 hours at most which are liquid accelerator cartridge, two-component resin cartridge, and mechanical expansion shell. Friction force from the grout body also enables rock bolts to prevent the loosening of different geology layers. It also prevents rusting by covering the metal parts eliminating the chance of water getting into the connection. Based on different geology conditions and physical performances of tunneling rock bolts, there are different designs of rock bolts including the following: Fully threaded rock bolts:

A: Enough space for cuttings to evacuate the hole efficiently; B: High-performance design for harsh and abrasive conditions formations; C: Components Replace Easy to Save Drill Cost; D: Choose Right DTH Drill Rods; E: Choose Right Friction-welded joints; A: Enough space for cuttings to evacuate the hole efficiently: As experienced, the smallest hole diameter a DTH hammer can drill is its nominal size. i.e. standard 102 mm (4 inches) hammer will drill a hole down to a minimum diameter of 102 mm (4 inches). The limiting factor is the outside diameter of the hammer dth, because as the hole diameter reduces due to diameter wear of the dth hammer bit, airflow is restricted. Maximum hole size for production drilling is the nominal hammer size plus 25 mm (1 inch), so for a 102 mm (4 inches) hammer the maximum hole size is 127-130 mm (5 inches). The right drill bits are determined by the type of application, hole size, and type of rock formation, the size of the hammer DTH should match the required hole dimension as closely as possible, leaving just enough space for cuttings to evacuate the hole efficiently. B: High-performance designed DTH Rock Tools for harsh and abrasive conditions formations: VD DRILL DTH hammers are purpose-matched for all rock types and applications where high performance and low total cost per drill meter are the main criteria. ) VD Drill’s DTH Hammer with a common design is a suitable choice for dth drilling in quarries, shallow water well drilling, and underground blast hole drilling. ) VD Drill’s standard DTH hammer is the optimum selection for demanding conditions in abrasive formations. It has the same internal components as the common design, but with larger OD of the drive chuck and wear sleeve. These also protect the top sub from excessive wear when rotating out of the hole through broken rock. Each hole hammer is made from quality alloy steel and has been precision machined to produce a perfect body, heat treated to the required hardness, given surface compression for fatigue resistance, and the head of DTH Hammer is fitted with a top sub-fitted with tungsten carbide buttons for wear protection in harsh and abrasive conditions. Each DTH hammer can be quickly and easily adjusted to different compressor air pressures and air volumes, making our hammers fit all drill rigs, operating at different altitudes and climates. C: Components Replace Easy

Operation Instruction Put DTH Hammer on the Bench Adjust the position of DTH Hammer and wrench; use a wrench to block the top subside of the hammer; let the wrench and jack in the same face. Fix K-Shaped base with a nut. Fix wrench with nuts. Shake handle of Jack slowly till the top sub away from hammer After the top sub is dismantled, release hydraulic oil pressure in the jack, release nuts, discharge the K-shaped base and turn around the Hammer. The part of the external cylinder thread is prohibited to wrap by the jaw to avoid any damage to the hammer dth. Adjust the position of hammer and wrench; use a wrench to block the drive bit of the hammer; let the wrench and jack in the same face. Fix hammer Fix K-Shaped base and the wrench with the nut. Shake handle of Jack slowly till dive chuck away from hammer dth.     For more about DTH Hammer Hydraulic Manual Breakout Bench Please read How to avoid DTH Bits loss in the hole with DTH Hammer Hydraulic Manual Breakout Bench : https://drillbitsupplier.com/how-to-avoid-dth-bits-loss-in-the-hole/   More information please contact our Expert or ask for a quote.

 Improve Threaded Design Keep Borehole Open Adopt DTH Hammer Breakout Bench Choose Right Thread Lubrication When the driller use drill rigs to drill holes, he runs the risk of loosing his dth drilling tooling, it is very important for DTH rock drill tools with suitable design, especially in thread design. Improve Threaded Design: If the threads are fixed design may be hard to unscrew, if for simple design, they may become unscrewed in the hole with the loss of dth button bits and retaining rings. VD Drill manufacturer adopt the 3-start thread design for bit dth, where there will be 3 threads following each other, instead of just the one that is common on a simple bolt and nut. Keep Borehole Open: The 3-start thread makes it easier to unscrew components and if the pitch is right then it is less likely to become unscrewed in the hole, although this can happen in soft ground conditions, may be made up of broken or fissured rock, clays, sands or damp heavy conditions where dust can cling to the wall of the hole. – usually as the driller attempts to clear a blocked hole, Naturally it is important to keep the borehole open during the dth drilling process. To keep DTH Tools with good effect without loss, there are two further ways below: Adopt DTH Hammer Breakout Bench: Even with a 3-start thread arrangement, the tool that has been on the rig for a time or has been used in the difficult ground with a powerful drill rig is likely to have screwed up so tight that it is nigh impossible to loosen it, therefore, change DTH bit or Strip the DTH Hammer Bit only to find that it cannot be dismantled without extreme difficulty. Then Drillers then resort to bashing the case around the thread with a sledgehammer that can cause serious damage to this region which may then result in catastrophic cracking of the Wear-Sleeve or Chuck so that the parts then become un-serviceable. Having the right tools, such as correctly fitting spanners and utilizing the hydraulic wrench on the rig or using a purpose-made stripping bench, can save a lot of time and money and avoid damaging hole hammer components. VD Drill manufacturer has provide own Hydraulic manual Breakout Bench or Hydraulic Automatic Breakout Bench, help the driller change parts on DTH tools. Choose Right Thread Lubrication: Thread lubrication is important too,

Two common methods of drilling approaches are used in industrial applications, Down The Hole Hammer Drilling and Top Hammer Drilling methods, which perform similar functions but in different ways. To develop more efficient and cost-effective means of drilling to greater depths, here we talk about how to use the drilling methods to save cost-effectively. Difference Drilling Methods DTH Drilling / Down The Hole Hammer Drilling DTH Drilling is more accurate than TOP Hammer Drilling, DTH rigs use compressed air to drive the hammer behind the drill bit through dth drill rods, the piston directly hits dth button bit, and the hammer cylinder provides a straight and stable guide for the drill bit. This keeps the effects of energy from being lost in the joints,  DTH rigs drill straight holes with less deviation providing more accurate blasting and better fragmentation as a result, and allowing deeper percussion drilling, DTH drills are proven at depths of more than 20 meters. In addition, producing less noise than TOP Hammer drills. DTH drilling is more suitable for large holes in hard rock drilling, typically the maximum hole size for DTH drilling in a production environment is 254-330mm, especially for rocks with a hardness of more than 200Mpa. However, for rocks below 200 MPa, not only energy will be wasted, but also the drilling efficiency will be low, which will cause serious wear on the dth drill bit. This is because when the hole hammer’s piston strikes, the soft rock cannot fully absorb the impact, which severely reduces the efficiency of drilling and slagging.  (DTH drills mainly use pressurized air for slag flushing, and sometimes air foam for special applications.) Top Hammer Drills The impact force of the top hammer drilling generated by the piston of the pump in the hydraulic drilling rig is transmitted to the drill bit through shank adaptor (shank joint) and drill rod, which is the most different from down-the-hole drill. Meanwhile, the percussion system drives the drilling system to rotate. When the stress wave reaches bit dth, the energy is transferred to the rock in the form of penetration by dth drill bit.  The percussive system strikes the drill rod, for example, 2,000-5,000 strikes per minute, and the rotation speed can be, for example, 60-200 rounds per minute. Together these elements make it possible to drill holes in the hard rock. The excess material (cuttings) is flushed up from the

DTH hammer, also called down the hole ( DTH) hammer, is a kind of pneumatic rock drilling tool, DTH hammer is an integral part of the DTH Rig. The difference from others is that during DTH drilling process, down the hole hammer always stays at the bottom of the hole, impacting the rock by bit from DTH hammer directly. The rotating power acting on DTH hammer comes from rotation motor on the drill rig, the pull force comes from feeding device and transfers the energy to DTH hammer through drill pipe; High-pressure air enters into the DTH hammer through DTH drill rods, then run out from DTH hammer bits, exhaust air is used to blow up cuttings from the bottom of the hole; The rapid hammering process shreds hard rock into small fragments and dust, they are then blown away by a fluid, be it air, water, or the drilling mud itself. DTH Drilling technique was created to drill big holes vertically in ground boring drilling and other industrial applications, such as metallurgy, coal, chemical industry, water conservancy, hydropower, highway, railroad, national defense, construction, and other engineering hole-forming operations. You should keep the following points in mind while choosing the right DTH hammer for your projects: 1. DTH Hammer Size:The selection of DTH hammer size is largely determined by the hole diameter and type of rock formation, 3.5 to 10 inches is the best range of blast holes for DTH drilling. Smaller holes are typically drilled with a top hammer rather than a DTH hammer, and larger holes generally use the rotary drilling technique; DTH rigs drill straight holes with less deviation providing more accurate blasting and better fragmentation as a result. the size of the DTH hammer should be selected as close as possible to the size of the hole to be drilled. The larger the diameter of the DTH hammer, the larger the diameter of the piston, and the higher the working efficiency. Ideally, the size of the hammer should match the required hole dimension as closely as possible, leaving just enough space for cuttings to evacuate the hole. Usually, the smallest hole diameter a DTH hammer can drill is its nominal size. i.e. standard 127 mm (5′) hammer will drill a hole down to a minimum diameter of 127 mm (5′). The limiting factor is the outside diameter of the DTH hammer, because as the hole diameter reduces