What Are The Differences between R thread and D Thread Anchor Bars

The anchor bar thread types mainly include D thread, R thread, and T thread. Different thread shapes have an impact on the bearing capacity and other properties of the anchor bars. For self-drilling anchor bolts, the technology which integrates drilling and grouting has high requirements for the performance of the anchor bars, so the R thread anchor bar is generally used as the rod body. This article will introduce the difference between the D thread anchor bar and the R thread anchor bar in detail.


Introduction of the D thread anchor bar and the R thread anchor bar

At present, the common hollow anchor bars on the market mainly have two thread shapes, R thread, and D thread. The thread pitch of D-type is mostly 12 and 13mm, and there are other sizes. The main feature is that the top of the tooth is flat, and the bottom of the tooth is arc-shaped, the tooth depth is generally 1-1.2mm. The tooth top and flat of the R thread are arc-shaped.

R threadV.S. D thread


The difference between the D thread and the R thread

The difference between D thread and R thread is mainly in the outer diameter, tooth depth, tooth shape, pitch, chamfer, interfit, etc. There are also differences between different manufacturers or even different batches from the same manufacturer. So the data below is for reference only.


D Thread Anchor Bars

R Thread Anchor Bars

outer diameter

Generally larger than the nominal value, such as D25 outer diameter is generally between 25-25.5mm

Generally smaller than the nominal value, generally the outer diameter of R25 is between 24.44-24.74mm

tooth depth

The standard requires between 1.5-2mm, and the actual is generally <1.3mm

Generally between 1.5-1.7mm

tooth shape

There is no exact standard, and there are certain differences between different manufacturers.

Conforms to the standard of drilling tools and the shape standard is relatively fixed


Generally between 8-13mm, mostly 12.7mm

12.7mm on average


Without chamfer

With chamfer


Hollow anchor bars and accessories from different manufacturers cannot match, and there is a risk of poor cooperation between bar bodies and accessories from different batches of the same manufacturer

Different batches of R thread anchor bars and accessories from the same manufacturer or different manufacturers can cooperate with each other


Thread requirements for self-drilling bolts

sinorock r38 hollow anchor bar

The common D-thread hollow anchor bars usually adopted the construction process of drilling first and then placing the anchor bars, so the rod body does not need to bear the force during installation. However, when drilling with the self-drilling hollow anchor bars, the rod body needs to withstand the force from impact, torque, and resistance to be bent. Therefore, the rod body and thread are required to have the sufficient bearing capacity, so that the rod body will not break or plastically deform during construction. The tooth shape of the D-thread anchor rod determines that the tooth depth is relatively shallow, and the size is not standard enough, resulting in a loose fit between D-thread anchor bars of the same specification. During the construction process, it is easy to fall off or difficult to disassemble, and the thread is worn and cannot be constructed. If the D-thread anchor bar is used as the self-drilling anchor bolt, it will cause thread deformation and wear, the rod body will bend, and the quality will be uneven, and it will break during the drilling process.


The above is the introduction of what is the difference between the D-thread and the R-thread anchor bars. Self-drilling anchor bolts are more commonly used in broken rock formations with relatively harsh conditions. They have high requirements for the force value of the rod body, and there are different requirements from material to thread shape. Sinorock provides R thread and T thread self-drilling hollow anchor bars. Welcome contact at sinorock@sinorockco.com.



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