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The optimum range of hole size for blast hole drilling with DTH is 90 mm to 254 mm (3 ½”–10″). Smaller blast holes are generally drilled using tophammer, and larger holes generally use rotary machines.
In other applications, like foundation drilling, DTH hammers can be used with single bit in hole sizes up to . 750 mm (30″). With multiple hammer units CD (Cluster drills) drill holes up to 70″ or 1778 mm.
As a rule of thumb, the smallest hole diameter a DTH hammer can drill is its nominal size. A 4 inch hammer will drill a 4 inch (102 mm) hole. The limiting factor is the outside diameter of the hammer, because, as hole diameter reduces, airflow is restricted. Maximum hole size for production drilling is the nominal hammer size plus 1 inch, so for a 4 inch hammer the maximum hole size is 5 inch (127–130 mm).
Choosing the right hammer is largely determined by hole size and type of rock formation. 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.
Q: Are you trading company or manufacturer ?
A: We are factory.
Q: How many workers in your factory?And what is your company scale?
Area of our factory: over 50,000SQM;
Numbers of our employees: Over 700;
Numbers of our equipment &facilities: Over 1000 sets
Numbers of DTH Hammer production yearly: Over 20,000 sets
Numbers of Drill bits production yearly: over 250,000 pcs
Annual turnover in USD: 60 Million
Market share(China): 40%-50%
Export market volume: 30 Million USD
Q: How long is your delivery time?
A: Generally it is 25 working days.
Q: Do you provide samples ? is it free or extra ?
A: Yes, we will charged the sample but will return it back to you in your bulk order.
Q: What is your terms of payment ?
A: Usually we accept T/T and L/C, but it is negotiable.
