Milled-Tooth vs. TCI Tricone Bits: Making the Right Choice

When it comes to drilling through various formations—whether for oil, gas, mining, or trenchless engineering—the tricone bit remains one of the most trusted tools in the industry. But a crucial decision must be made before the bit hits the ground: Should you choose a Milled-Tooth (MT) or a Tungsten Carbide Insert (TCI) Tricone Bit?

This blog breaks down the core differences between milled-tooth and TCI tricone bits, their use cases, pros and cons, and how to choose the right one for your drilling project. Whether you're in soft, abrasive formations or hard, compact rock, choosing the right bit affects performance, tool life, and overall ROI.

What Is a Tricone Bit?

A tricone bit consists of three rotating cones, each equipped with cutting structures that crush or shear rock as the bit rotates. These bits are categorized based on the cutting elements:

• Milled-Tooth (MT): Steel teeth machined directly from the cone body.

• TCI (Tungsten Carbide Inserts): Tungsten carbide buttons pressed into holes in the cone for greater durability.

Milled-Tooth Tricone Bits: Features and Applications

Key Characteristics

• Machined from a single piece of steel (integrated with cone)

• Larger tooth spacing for improved cleaning in sticky formations

• Typically unsealed or open-bearing designs

Best for:

• Soft to medium-soft formations

• Unconsolidated sandstones, clays, or shale

• Drilling environments where high penetration rates (ROP) are needed

Advantages

• High ROP in soft formations

• Lower cost compared to TCI

• Simpler design, easier to manufacture

Limitations

• Poor wear resistance in abrasive formations

• Shorter tool life

• Limited performance in hard or interbedded rock layers

TCI Tricone Bits: Features and Applications

Key Characteristics

• Tungsten carbide inserts brazed into the cone structure

• Enhanced wear resistance and durability

• Available in sealed-bearing designs for longer life

Best for:

• Medium to hard formations (e.g., limestone, basalt, granite)

• Deep well drilling and high-pressure environments

• Applications requiring longer tool life and stable penetration

Advantages

• Superior wear resistance

• Better performance in hard rock

• Sealed bearings extend operational hours

Limitations

• Higher upfront cost

• Slightly lower ROP in soft formations

• Can chip under shock loads in extremely hard formations

Comparison Table: Milled-Tooth vs. TCI Tricone Bits

When to Use Milled-Tooth Bits

• Projects where drilling speed outweighs longevity

• Shallow wells or temporary access holes

• Situations where budget constraints limit the use of premium tools

• Unconsolidated formations that might clog TCI inserts

When to Use TCI Tricone Bits

• Long horizontal or deep vertical wells

• Harsh, abrasive, or fractured formations

• Applications demanding longer tool life and minimal bit trips

• When drilling costs per foot are a critical KPI

People Also Ask 

1. What is the difference between TCI and milled tooth bits?

The key difference lies in the cutting structure: TCI bits use tungsten carbide inserts for harder formations, while milled-tooth bits have steel teeth better suited for soft rock.

2. Are TCI bits better than milled tooth?

Not always. TCI bits are more durable and ideal for hard formations, but milled-tooth bits often outperform them in soft rock due to their higher ROP and lower cost.

3. Can I use a milled-tooth bit in hard formations?

It's not recommended. Milled-tooth bits wear rapidly in hard or abrasive formations, leading to poor performance and increased operational costs.

Sanlong Petroleum's Tricone Bit Solutions

At Sanlong Petroleum, we offer a full range of tricone drill bits from 3" to 26", engineered to meet API 7-1 and ISO standards. Whether you’re looking for a rugged TCI bit for hard formations or a high-speed milled-tooth bit for clay or shale, we can customize to match your project geology and budget.

Our Offerings Include:

• TCI Tricone Bits with sealed roller or journal bearings

• Milled-Tooth Bits optimized for high ROP in soft rock

• Hybrid Drill Bits combining PDC and roller cone technologies

• Special coatings and custom nozzles for abrasive environments

Sanlong bits are trusted in oil, gas, geothermal, mining, and HDD projects worldwide, with exports to the US, Turkey, South Africa, Russia, and beyond.

How to Choose the Right Tricone Bit Type

✅ Factors to Consider:

• Formation Type & Abrasiveness

• Bit Size Requirements

• Drilling Method (Rotary, HDD, Vertical)

• Desired ROP vs. Bit Life

• Budget vs. Performance Priorities

A reliable supplier like Sanlong Petroleum can assist you in analyzing borehole conditions and recommending the most appropriate bit type, size, and cutter material.

Choosing between milled-tooth and TCI tricone bits doesn’t have to be confusing. By understanding the formation, budget, and performance demands of your project, you can select a tool that enhances efficiency, reduces downtime, and maximizes ROI.

At Sanlong Petroleum, we’re ready to assist you with custom-engineered drilling tools, superior customer service, and fast global delivery.