That is Why You Need to Use Carbide Twist Drills Instead of HSS
In the cutting industry, carbide twist drills are gradually replacing high-speed steel twist drills.
Due to the high hardness of carbide, they can remain sharp for longer periods of time and cut at higher speeds. Especially when cutting certain materials, they have an overwhelming advantage over high-speed steel drill bits.
Carbide Twist Drills Introduction
Twist drills are the most basic yet critical tools in industrial processing, mold manufacturing, and mechanical drilling. The name “twist drill” comes from its spiral-shaped flutes. Additionally, it is widely used due to its excellent cutting performance, chip removal capability, and centering ability.
A typical twist drill consists of the following parts:
Shank: Connects to the machine tool spindle to transmit rotational and axial forces.
Spiral flutes: Participate in chip removal and coolant delivery.
Cutting edges: The core functional area that actually performs the drilling operation.
Operating principle: The drill rotates, using the cutting edges to compress or cut the surface material of the workpiece. Chips are expelled from the bottom of the hole along the spiral flutes. Simultaneously, coolant flows through the spiral flutes to cool the cutting edges.
Despite its simple structure, the performance of a twist drill is highly dependent on the material used, which is why carbide twist drills are gradually replacing high-speed steel drills.
High-speed steel VS cemented carbide
1.Introduction to high-speed steel
High-speed steel is a type of tool steel with high hardness. It is produced through a high-temperature quenching and tempering process to achieve high hardness (HRC62-65) and good toughness. Since its invention in the late 19th century, it has remained in use today, with many different grades developed to suit different working conditions.
Advantages of high-speed steel drill bits
Good toughness: High impact resistance, suitable for processing soft materials or intermittent cutting.
Low cost: Cheap raw materials, simple manufacturing process, and a unit price that is only one-third that of carbide drill bits.
Easy to process: The cutting edge parameters can be adjusted manually using a grinding wheel.
Limitations
Poor heat resistance: Insufficient red hardness; hardness significantly decreases when cutting temperatures exceed 600°C, accelerating wear.
Weak wear resistance: Insufficient edge strength when machining hard materials or during high-speed cutting, leading to wear and rough hole walls.
Short service life: When machining difficult-to-machine materials, the service life is only 1/5 to 1/3 of that of carbide drill bits.
2. Introduction to carbide
Carbide is made by sintering tungsten carbide (WC) as the base material with the addition of cobalt (Co) and other metal binders.
It has a hardness of HRA89-94 (equivalent to HRC90-95), which is far superior to high-speed steel in terms of hardness and heat resistance. Although it is more expensive, cemented carbide drill bits now account for a larger share than high-speed steel drill bits in mass production and the processing of difficult-to-machine materials.
Advantages of Carbide Twist Drills
High Wear Resistance: Maintains a sharp cutting edge even at high cutting speeds due to its ultra-high hardness.
High Temperature Resistance: Can continue to operate in environments up to 1000℃ with minimal hardness degradation.
High Rigidity: Under stable clamping conditions, it can achieve more precise drilling (±0.01mm accuracy) and smoother surface roughness.
Long service life: Under the same material processing conditions, its service life is 5-10 times longer than that of high-speed steel drill bits.
3 Scenarios to Help You Choose Tungsten Carbide Twist Drills
1. Machining Difficult-to-Machine Materials (Stainless Steel, Titanium Alloys, High-Temperature Alloys)
These materials share the common characteristics of high hardness, high toughness, poor thermal conductivity, and a tendency for heat to concentrate at the cutting edge, leading to edge burning and reduced hardness.
High-speed steel experiences a sharp drop in hardness at 600°C, effectively losing its ability to machine these materials.
In contrast, carbide maintains its cutting performance even at 1000°C. Additionally, some carbide drill bits feature internal cooling, which enhances temperature control, enables efficient chip removal, and maintains continuous cooling, resulting in extended tool life.
2. High-speed cutting and precision drilling
The spindles of current CNC machine tools and machining centers are extremely strong and can support speeds of over 20,000 rpm. However, high-speed steel is only suitable for low speeds of 8,000 rpm, and excessive speeds can cause breakage.
In contrast, carbide tools are highly suitable for high-speed machining. Within the appropriate speed range, excessively low speeds can actually cause brittle fracture. In high-speed machining, carbide tools ensure excellent cutting performance, surface finish, and hole diameter consistency.
3. Batch Processing
Although high-speed steel drill bits have a cost advantage initially, in batch processing, we should focus more on downtime. The high wear rate of high-speed steel drill bits means that machines cannot maintain continuous operation and require frequent tool changes. Over time, this will lead to a gradual increase in overall costs.
Carbide drill bits, with a lifespan several times longer than high-speed steel drill bits, can significantly reduce downtime. Under the same conditions, as time increases, the average cost of carbide drill bits will be lower than that of high-speed steel drill bits.
Exceptions: Scenarios suitable for high-speed steel twist drills
In a few scenarios, high-speed steel twist drills still offer high cost-effectiveness.
Sample orders: In small-batch processing, high-speed steel drill bits are less expensive and are recommended for use.
Equipment limitations: Older machine tools have low spindle power and insufficient rigidity, making them more suitable for high-speed steel drill bits with better toughness.
Summary
Carbide twist drills have transitioned from “high-end tools” to mainstream options. An increasing number of factories are adopting them. Unless dealing with easy-to-machine small-batch orders or budget constraints, carbide drills are the optimal solution for enhancing competitiveness and reducing overall costs.
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