NHD Ultra-Fine-Grained Graphite Molds | Specifically Designed for The Hot-press Sintering Process of Diamond Drill Bits

Product Description:

A precision sintered core designed for geological drilling

In the manufacturing process of diamond core drill bits, graphite molds serve not only as forming containers but also play a critical role in determining the density and structural integrity of the drill bit matrix. Our graphite molds, specifically designed for diamond drill bits, are engineered to withstand the harsh conditions of geological drilling and mining operations.

Unlike standard molded graphite, we use high-purity isotropic graphite as the base material. During the hot-press sintering process, this material perfectly balances the thermal expansion differences between the steel body, the metal matrix, and the mold itself. We understand that microcracks appearing in drill bits during the cooling phase often stem from mold designs that fail to precisely match the material’s properties. Therefore, through exceptional dimensional stability and thermal performance, our products ensure that every drill bit achieves perfect geometric accuracy and mechanical strength upon demolding.

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Product Specifications and Customization Parameters

Parameter Items	Specifications	Note
Molding Process	Isostatic pressing	Ensure isotropy and eliminate directional variations in strength
Flexural strength	≥35 MPa	Withstands high-temperature, high-pressure sintering conditions
Bulk density	≥1.78 g/cm³	High-density structure with excellent impermeability
Dimensional tolerances	±0.05mm - ±0.1mm	Custom-made to meet the precision requirements specified in the drawings
Surface treatment	Polished/Impregnated Anti-Oxidation Coating	Improving Demolding Performance and Service Life

Product Advantages:

Technology-Driven Quality Assurance

• Overcoming the Challenge of “Cooling Cracks”

  A major industry challenge lies in the fact that the thermal expansion coefficients of steel and the matrix are significantly higher than that of graphite. During the cooling phase, conventional molds restrict the contraction of the matrix, causing immense tensile stress to build up inside the drill bit and resulting in cracks. We utilize specialty graphite materials with low thermal expansion coefficients and incorporate a clearance design that allows the matrix to contract freely during cooling, thereby significantly reducing the scrap rate.

• Superior Thermal Shock Resistance

  The sintering process involves extreme temperature cycling. Our molds undergo a special impregnation treatment that enhances oxidation resistance by over 30%, enabling them to withstand thousands of rapid cooling and heating cycles without structural fatigue or fracture, significantly extending mold service life.

• Seamless Demolding Experience

  Leveraging graphite’s natural self-lubricating properties, combined with our precision cavity polishing process , effectively prevents metal powders from infiltrating the mold’s micro-pores under high-temperature and high-pressure conditions. The demolding process is smooth and obstruction-free, avoiding damage to the drill bit’s cutting teeth caused by forced removal.

• High Purity Ensures Matrix Performance

  Mold ash content is strictly controlled below 500 ppm. The high-purity graphite material prevents chemical reactions with metal powders during high-temperature sintering, ensuring the chemical purity and cutting performance of the diamond drill bit matrix.

Product Specifications and Customization

Given the wide variety of diamond drill bit specifications, NHD offers fully customized machining services with no minimum order quantity (orders as small as one piece are accepted).

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This product is available in a variety of core mold specifications and features a highly polished inner surface. The resulting sintered drill bits have smooth inner bores, making them suitable for the production of diamond drill bits with varying inner diameters and structures. Customers do not need to create separate molds for each specification. A special surface treatment minimizes reactions with the matrix, prevents impurities from forming in the drill bit’s inner bore, and enhances the drill bit’s mechanical properties and service life.

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The pattern design on the bottom of this mold allows for the direct formation of chip evacuation channels and cooling channels in the drill body, optimizing chip evacuation efficiency and increasing drilling speed. It clearly illustrates the clearance between the core and the outer mold. A properly designed clearance is key to preventing “chip leakage” (where metal powder escapes under high temperature and pressure) and also ensures smooth demolding.

Product Applications:

Comprehensive coverage of the drilling industry

This product is widely used in the manufacturing of various types of diamond core drill bits and is suitable for industries including.

Geological Exploration & Core Drilling

Our graphite molds produce diamond core bits with high-density and uniform hardness, ensuring stable performance in complex geological formations, improving core recovery rate and exploration efficiency.

Mining & Hard Rock Drilling

Designed for high-intensity mining operations, our graphite molds produce impact-resistant diamond bits that reduce tooth breakage, extend service life, and adapt to continuous mining drilling.

Construction & Engineering Drilling

Our precision CNC-machined molds ensure high accuracy diamond bits for construction drilling, meeting the requirements of concrete, rock, and pile foundation projects, improving construction efficiency and safety.

FAQ：

• Q1: What is the primary use of your graphite molds?

  A: This series of graphite molds is specifically designed for the high-temperature hot-press sintering of diamond core bits, geological drill bits, and mining drill bits. They serve as essential forming consumables in the drill bit manufacturing process, are compatible with standard hot-press sintering equipment, and are widely used in the production of drill bits for hard rock drilling, geological exploration, and engineering drilling.

• Q2: Why do my graphite molds always stick to the drill body, making demolding difficult?

  A: The root cause is the high microscopic porosity of the mold surface. During hot pressing, molten metal seeps into these pores and forms a mechanical bond upon cooling. NHD’s ultra-fine graphite mold manufacturing process has been further refined to physically block the pathways for metal penetration, enabling easy demolding.

• Q3: What is the approximate service life of the mold?

  A: Compared to ordinary, low-quality graphite molds, this high-density graphite mold can withstand a higher number of cycles. Under normal sintering conditions, it wears slowly and is resistant to burn-out, significantly reducing the frequency of replacement and effectively lowering production costs for the factory.

• Q4: Can you customize molds based on my drill bit dimensions?

  A: We offer full-scale customization. We can perform precision CNC machining based on customer drawings, drill bit specifications, cavity structures, hole diameters, and overall dimensions. This includes non-standard designs such as core molds, sleeve molds, parting plates, and modular molds, all customized to your specific needs.