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R25 All Threaded Self-Drill Rock Bolt

The core of the Onton R25 All Threaded Self-Drill Rock Bolt is a hollow, thick-walled, central drilling rod with a drill bit at the top. The system is modular, meaning that the most appropriate configuration can be put together to suit on-site circumstances and the forces that apply.

You can see its application mainly in tunneling constructions. (NATM method)

The all threaded self-drill rock bolts are available in the steel grade S460NH and other common types. All of steel materials are produced according to EN 10210-1 “Hot finished structural hollow sections of non-alloy and none grain steels” and have excellent capacity to the short time simultaneously dynamic loads (torque, frequent percussion impact, bending moments) during drilling as long-term load and durability.

Working Process

The system is used to create anchors in soft or unstable ground. Drilling, positioning of the reinforcement and injection are carried out in a single operation, thereby avoiding the difficult task of drilling a casing hole.

A disposable drill bit is screwed onto the first rod. The steel hollow bar is then connected directly to the drill rig (if necessary using an injection swivel).

Drilling starts with simultaneous injection via the central hole in the bar. As the drill bit features a hole, the cement grout spreads into the ground as the drill moves forward.

When the first bar is fully inserted in the ground, injection and drilling are stopped, and the bar is unscrewed from the drill rig.

The second bar can then be coupled to the first bar and the machine, and operation can be resumed.

The following is a copy of publication in 1990s which described the operation methods of R25 self-drilling anchor rock bolts. It was original published by ontonbolt.

Operation Guide for R25 Self-Drilling Anchor Bolt

Operation Guide for R25 Self-Drilling Anchor Bolt

  • Matching System: Atlas/MAI Drilling Systems
  • Surface treatment: galvanised,epoxy
  • Material: Steel, S460
  • Usage: mining,tunnel,slope,foundation pit
 Typical technical performance for R25 All Threaded Self-Drill Rock Bolt:
R25 SDA Hollow Bar Specifications
SDA Size Outer Diameter (mm) Inner Diameter (mm) Ultimate Load (kN) Yield Load (kN) Weight (kg/m)
R25N 25 14.5 200 150 2.0
Other standards available on request

Threaded hollow bars (all lengths)

Hollow Bars have a continuous external thread with an R (rope thread) or T (trapezoidal thread) profile.


Flexibility in length by using couples. A specially designed stopping system ensures that the coupler is correctly positioned on the bars to be coupled.

Nuts and plates

The plates and nuts are used to create the anchor head. There are straight nuts and spherical nuts, each with their appropriate plates.

Drilling bits

Choice of drill bits for different ground conditions.

R25N Drill bits:
X R25/42, R25/51
EX R25/42, R25/51
EXX R25/42
ESS-F R25/42

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Drill Bits for self-drilling anchoring system
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