How to Choose Between Tapered Hole and Brazed Cold-Pressed Button Bits

In mining operations and rock drilling applications, selecting the right tungsten carbide button bit directly affects drilling efficiency, tool service life, and overall operating costs. Many purchasing professionals have found that even button bits labeled as "wear-resistant" can deliver significantly different service lives under actual working conditions. In many cases, these differences are related to whether the connection design and manufacturing process are properly matched to the drilling application.

From a practical workshop and field-use perspective, this article explores several key considerations when selecting and using tapered hole button bits and brazed cold-pressed button bits, helping equipment managers and purchasing professionals make more informed decisions.

1. Connection Design Determines Impact Energy Transmission

The first step in selecting a button bit is to match its connection design to the impact energy of the drilling equipment.

Tapered hole button bits rely on an interference fit between the mating tapered surfaces to transmit impact energy. Therefore, taper angle, dimensional accuracy, and surface finish are critical to ensuring a secure connection and stable performance.

Brazed cold-pressed button bits, on the other hand, rely on the combined support of the brazed joint and residual stresses introduced during the cold-pressing process. This design can be suitable for drilling applications involving relatively low to moderate impact energy and layered rock formations, depending on the bit design and manufacturing quality.

When brazed structures are exposed to impact loads beyond their intended operating range, fatigue cracks may develop around the brazed joints.

In practical applications, it is advisable to check the impact energy and drilling specifications of the machine before purchasing. The taper dimensions of the drill rod should also be verified against the supplier's specifications. For example, models such as UP74002 and specifications such as T40 should be confirmed against the actual connection requirements.

Matching the bit to the drilling equipment from the beginning helps avoid unnecessary modifications and additional costs.

2. Button Protrusion and Button Arrangement Affect Drilling Efficiency

The protrusion height and arrangement of tungsten carbide buttons directly influence rock fragmentation efficiency, chip removal, and self-sharpening performance.

If the buttons protrude too little, rock fragments may not be discharged efficiently, reducing drilling speed. Excessive protrusion, however, can leave the carbide buttons inadequately supported, increasing the risk of button breakage when drilling hard rock.

Button arrangement is another important consideration. Compared with conventional circular arrangements, staggered or flower-shaped button layouts can provide multiple points of contact with the rock surface. Depending on the formation characteristics and bit design, this arrangement may help distribute impact loads and reduce the risk of core jamming in fractured rock formations.

During routine inspections, operators can use a vernier caliper to measure the distance from the button tip to the bit face. It is also important to check whether the flushing channels between the buttons are clear and unobstructed.

Button bits manufactured using pressure sintering furnaces and CNC machining centers generally offer better dimensional consistency in button pockets and flushing channels. Nevertheless, batch sampling and inspection are still recommended upon delivery.

3. Carbide Grade Selection Requires a Balance Between Toughness and Wear Resistance

The wear resistance of tungsten carbide buttons is not determined by surface hardness alone. A proper balance between hardness, toughness, and impact resistance is essential for reliable performance.

Common carbide grades such as YG6 and YG8 are generally used in medium-hard rock drilling applications, while grades such as YL10.2 may be considered for demanding hard-rock applications involving higher impact loads. The final selection should always be based on actual operating conditions and the manufacturer's material specifications.

Some manufacturers focus excessively on improving wear resistance by adjusting cobalt content without adequately considering toughness. However, an unsuitable material composition may increase the risk of brittle fracture under repeated impact loads.

Purchasing professionals should therefore request material inspection reports and verify key parameters such as cobalt content and carbide grain size.

For example, Zhuzhou HAO CARBIDE Cemented Carbide Co., Ltd. offers button bit materials covering a range of grades from YG6 to YG20C. This allows customers to select suitable carbide grades according to rock hardness, impact conditions, and specific drilling requirements rather than relying on the general description of "wear-resistant."

4. Taper Hole Accuracy Is Essential for Stable Assembly

For tapered hole button bits, dimensional accuracy directly affects assembly stability and drilling performance.

One common failure mode occurs when the tapered mating surfaces become worn, resulting in radial movement or looseness during operation. This can contribute to hole enlargement, drilling deviation, and accelerated tool wear. Insufficient control of concentricity during machining may also contribute to these problems.

During incoming inspection, the bit can be mounted on a standard taper shank, and a dial indicator can be used to measure face runout. If the measured runout exceeds 0.05 mm, the product should be evaluated against the agreed technical specifications, and a return or corrective action may be necessary.

The tapered hole surface should also be free from dents, corrosion, and other visible defects that could compromise the interference fit.

Suppliers equipped with precision machining capabilities of up to 0.002 mm, along with inspection instruments such as profile projectors and hardness testers, are better positioned to perform dimensional inspections according to customer drawings and technical requirements.

For buyers, specifying taper accuracy, concentricity, and inspection standards in the technical agreement is an effective way to improve product consistency.

Conclusion

Choosing the right tungsten carbide button bit requires more than simply comparing prices or wear-resistance claims. Three essential factors should guide the selection process:

• Connection design and impact conditions: Ensure that the bit connection is suitable for the impact energy and drilling equipment.

• Carbide grade and rock formation: Select the appropriate balance of toughness and wear resistance according to the hardness and characteristics of the rock.

• Taper hole accuracy and assembly requirements: Verify dimensional precision and connection stability to minimize premature wear and drilling problems.

Purchasing professionals are encouraged to include these requirements in their technical purchasing agreements and maintain batch inspection records for quality control.

As a manufacturer specializing in cemented carbide mining tools, Zhuzhou HAO CARBIDE Cemented Carbide Co., Ltd. offers a range of products, including tungsten carbide buttons, HPGR studs, and TBM cutter inserts. With integrated manufacturing capabilities from carbide blanks to precision machining, the company provides various product specifications to meet different mining and drilling requirements.

Its product range and manufacturing capabilities can serve as a useful reference when evaluating suppliers of tapered hole button bits and brazed cold-pressed button bits.