Is DTH drilling better than top hammer?

Power tool

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A corded hammer drill next to a drill bit and a chuck key

A hammer drill, also known as a percussion drill or impact drill, is a power tool used chiefly for drilling in hard materials.[1][2] It is a type of rotary drill with an impact mechanism that generates a hammering motion. The percussive mechanism provides a rapid succession of short hammer thrusts to pulverize the material to be bored, so as to provide quicker drilling with less effort. If a hammer drill's impact mechanism can be switched off, the tool can be used like a conventional drill to also perform tasks such as screwdriving.

History

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Ancient China's principal drilling technique,[3] percussive drilling, was invented during the Han dynasty. The process involved two to six men jumping on a lever at rhythmic intervals to raise a heavy iron bit attached to long bamboo cables from a bamboo derrick.[4][5][6] Utilizing cast iron bits[7] and tools constructed of bamboo, the early Chinese were able to use percussion drilling to drill holes to a depth of 3,000 ft (910 m). The construction of large wells took more than two to three generations of workers to complete.[8] The cable tool drilling machines developed by the early Chinese involved raising and dropping a heavy string of drilling tools to crush through rocks into diminutive fragments.[9] In addition, the Chinese also used a cutting head secured to bamboo rods to drill to depths of 915 m (3,002 ft).[10] The raising and dropping of the bamboo drill strings allowed the drilling machine to penetrate less dense and unconsolidated rock formations.[11]

In J.J. Couch invented the first pneumatic percussion drill.[12][13][14]

The origin of the first hammer drill is a matter of contention. German company Fein patented a Bohrmaschine mit elektro-pneumatischem Schlagwerk ("drill with electro-pneumatic striking mechanism") in . German company Bosch produced the first "Bosch-Hammer" around in mass production. The US company Milwaukee Electric Tool Corporation states that in , it was selling a lightweight 1&#;4 in (6.4 mm) electric hammer drill (cam-action).[15]

Hand-cranked percussion drills were made in the UK in the mid-twentieth century.[16]

Design

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Hammer drills have a cam-action or percussion hammering mechanism, in which two sets of toothed gears mechanically interact with each other to hammer while rotating the drill bit. With cam-action drills, the chuck has a mechanism whereby the entire chuck and bit move forward and backward on the axis of rotation.

This type of drill is often used with or without the hammer action, but it is not possible to use the hammer action alone as it is the rotation over the cams which causes the hammer motion. A hammer drill has a specially designed clutch that allows it to not only spin the drill bit, but also to punch it in and out (along the axis of the bit).

The actual distance the bit travels in and out and the force of its blow are both very small, and the hammering action is very rapid&#;thousands of "BPM" (blows per minute)[17] or "IPM" (impacts per minute). Although each blow is of relatively low force, these thousands of blows per minute are more than adequate to break up concrete or brick, using the masonry drill bit's carbide wedge to pulverize it for the spiral flutes to whisk away.

For this reason, a hammer drill drills much faster than a regular drill through concrete, brick, and thick lumber. In standardized drilling speed tests, the most effective hammer drills improve drilling speeds by upwards of 30% compared to completing the same task with the hammer mode disabled.[18] Hammer drills are increasingly powered by cordless technology.

Uses

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Holes in hard materials are needed for anchor bolts, concrete screws and wall plugs. Hammer drills are not typically used for production construction drilling, but rather for occasional drilling of holes into concrete, masonry or stone. They are also used to drill holes in concrete footings to pin concrete wall forms and to drill holes in concrete floors to pin wall framing. SDS rotary drills are more commonly used as dedicated masonry drilling tools in construction.

Hammer drills almost always have a lever or switch that locks off the special "hammer clutch," turning the tool into a conventional drill for wood or metal work. Hammer drills are more expensive and more bulky than regular drills, but are preferable for applications where the material to be drilled&#;concrete block or wood studs&#;is unknown. For example, an electrician mounting an electrical box to a wall would be able to use the same hammer drill to drill into either wood studs (hammer disabled) or masonry walls (hammer enabled).

See also

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• Rotary hammer &#; type of rotary drill

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• Volatiles Investigating Polar Exploration Rover &#; Canceled NASA lunar rover

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References

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In the dynamic world of rock drilling, two prominent techniques have emerged as frontrunners: Down-the-Hole (DTH) drilling and Top Hammer drilling. These methods have their unique features and advantages, making them popular choices in various applications. In this article, we will delve into the intricacies of both techniques, comparing their strengths, weaknesses, and the scenarios where each excels. By the end of this read, you'll have a comprehensive understanding of whether DTH drilling or Top Hammer drilling is the superior choice for specific drilling endeavors.

 DTH Drilling - Pioneering Penetration Rates and Efficiency

Down-the-Hole (DTH) drilling is renowned for its outstanding penetration rates and efficiency, making it an ideal choice for deep-hole drilling. The DTH technique involves a pneumatic hammer that drives a drill bit down into the rock with its percussive action, chipping away at the formation. Key advantages of DTH drilling include:

1.Deep Drilling Capability: DTH drilling is particularly effective in deep-hole applications, allowing for precise and reliable drilling at significant depths.

2.Low Deviation: The straightness and accuracy of DTH drilling ensure minimal deviation, making it suitable for projects where precision is critical.

3.Versatility: DTH drilling can handle various rock types, ranging from soft to extremely hard formations, making it a versatile option for diverse geological conditions.

4.Reduced Hole Deviation: The guidance provided by the drilling rod directly attached to the bit minimizes hole deviation during the drilling process.

 Top Hammer Drilling - Optimal for Surface Applications and Smaller Holes

Top Hammer drilling, on the other hand, utilizes a percussive mechanism mounted on the top of the drill string. This method is favored for its efficiency in surface drilling and smaller-scale projects. Key advantages of Top Hammer drilling include:

1.Speed and Efficiency: Top Hammer drilling excels in surface drilling applications, offering higher drilling speeds and efficiency for shallower holes.

2.Lower Equipment Cost: As compared to DTH drilling, Top Hammer equipment generally incurs lower initial costs, making it attractive for projects with budget constraints.

3.Ideal for Cohesive Formations: Top Hammer drilling is particularly effective in cohesive rock formations, providing reliable performance in such geological conditions.

4.Ease of Maintenance: The top-mounted design of the hammer simplifies maintenance and reduces downtime, contributing to increased productivity.

The Right Choice for the Right Application

While both DTH and Top Hammer drilling techniques have their strengths, selecting the appropriate method depends on various factors, including:

1.Drilling Depth: For deep-hole drilling projects, where straightness and precision are crucial, DTH drilling emerges as the superior choice.

2.Geological Conditions: The hardness and composition of the rock formation significantly impact drilling performance. DTH drilling's adaptability to varying rock types makes it a versatile option, while Top Hammer excels in cohesive formations.

3.Project Scale: Smaller-scale surface drilling projects often benefit from the speed and cost-effectiveness of Top Hammer drilling.

4.Budget and Investment: Companies must consider their budgetary constraints and long-term investment plans when deciding between DTH and Top Hammer drilling equipment.

In conclusion, DTH drilling and Top Hammer drilling each have their niche in the world of rock drilling. DTH's efficiency in deep-hole drilling and versatility in various geological conditions position it as the preferred choice for demanding projects. Meanwhile, Top Hammer drilling's swiftness, cost-effectiveness, and suitability for cohesive formations make it a viable option for certain surface drilling applications. By understanding the nuances of these techniques and carefully evaluating project requirements, drilling professionals can make informed decisions to optimize performance and achieve exceptional results in their rock drilling endeavors.

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