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Published by VMT at Jun 30 2025 | Reading Time：About 2 minutes
In precision CNC machining, material selection is critical. A small miscalculation in density can affect everything—from performance and weight to safety and regulatory compliance. Many CNC machining factories and services rely on lead due to its unique characteristics, but failing to understand the correct density can result in machining errors, material waste, or functionality failure. If you're manufacturing CNC machining parts like radiation shields, battery components, or custom weights, understanding lead’s density is not optional—it’s essential. This article breaks down everything you need to know about lead density, how it's measured, how it varies, and why it's so important in CNC milling and CNC turning operations.
Lead has a standard density of approximately 11.34 g/cm³, equivalent to 11,340 kg/m³ or 0.410 lb/in³. This makes it one of the densest commonly used metals in CNC machining parts, especially where weight, shielding, and vibration control are required.
Now that we know the standard density of lead, let's dive deeper into its various units, influencing factors, and how this crucial property affects CNC machining decisions. From selecting the right alloy to fine-tuning the cutting process, knowing the density of lead helps CNC machining factories deliver precision and performance consistently.
Interested in how lead compares to aluminum, stainless steel, or copper in CNC milling? Explore our guides on metal properties in CNC turning and how density affects chip load and feed rate.
Key Points
Lead (chemical symbol: Pb) is a soft, malleable, and highly dense metal. It’s resistant to corrosion and is commonly used in applications requiring weight or radiation protection. In the CNC machining industry, it’s valued for parts requiring mass and stability, such as counterweights, radiation shielding, and vibration dampeners. Its machinability allows for precise CNC milling and CNC turning, even at complex geometries.
What Is the Density of Lead?
Density is defined as mass per unit volume. For lead, its standard density is:
This is equivalent to 11.34 g/cm³, a commonly used expression in industrial design, alloy analysis, and material comparison.
Approximately 0.410 lb/in³, this unit is suitable for imperial system applications, such as ballast design in shipbuilding or heavy component engineering in the U.S. and other imperial-based industries.
These values are crucial when designing or machining CNC parts to ensure correct mass and function.
Pure lead, with minimal impurities, has a consistent density of 11.34 g/cm³ under standard temperature and pressure (STP). However, this value can vary slightly if the lead is alloyed or contains residual contaminants—something CNC machining factories must account for during production planning.
When used for CNC machined parts—such as components that undergo casting followed by CNC machining or turning and polishing—it is essential to account for slight deviations caused by factors like processing temperature, cutting heat, and tooling tolerances. These variables can subtly affect material density, dimensional stability, and overall part performance.
For CNC machining services, knowing the density of lead isn’t just theoretical—it directly affects:
Whether you’re involved in CNC milling or turning, having the exact density in mind allows for smarter material selection and better product results.
Temperature
As temperature increases, lead expands, slightly reducing its density. This is critical during CNC machining processes that generate heat.
Pressure
While solids like lead are relatively incompressible under normal conditions, extreme pressure environments may cause minor density changes—important for aerospace and deep-sea applications.
Alloys and Impurities
Adding elements like tin or antimony to lead (common in CNC machining for strength or hardness) alters its density. CNC machining factories must measure alloy density accurately to avoid deviations in part weight or performance.
When selecting materials for CNC machining parts, understanding density is essential. In industries like aerospace, medical, defense, and electronics, density affects everything from performance and stability to radiation shielding and part weight. Lead, known for its high density, is frequently compared to other industrial metals like aluminum, iron, stainless steel, copper, zinc, titanium, and gold. CNC machining factories must carefully evaluate these properties when choosing the most suitable material for CNC milling or CNC turning processes. Let’s take a detailed look at how lead's density compares to other metals commonly used in CNC machining services.
Aluminum is known for its light weight and excellent machinability, making it a favorite for CNC milling and CNC turning in automotive and aerospace industries. Compared to lead, aluminum is almost 4.2 times less dense, meaning parts made from aluminum are significantly lighter. While aluminum lacks the weight and shielding properties of lead, it's ideal where low mass and high strength-to-weight ratio are required.
Iron is denser than aluminum but still ~30% less dense than lead. It offers strength and magnetic properties that lead does not, making it useful in mechanical CNC parts and structural components. Iron is also less toxic and more commonly accepted in environmental regulations, although it lacks the damping and shielding capabilities of lead.
Stainless steel is a versatile material used in CNC machining for parts requiring corrosion resistance and mechanical durability. While denser than iron, it is still ~28% lighter than lead. Stainless steel is preferred over lead when hygiene, strength, and appearance are prioritized, such as in medical or food-grade CNC applications.
Copper offers excellent thermal and electrical conductivity and is widely used in electronics and heat-exchange CNC components. Though denser than stainless steel, copper is still ~20% less dense than lead. Lead is favored in CNC machining when mass or radiation shielding is needed, while copper is chosen for electrical performance.
Gold
Gold is significantly denser than lead—about 70% more. However, due to its cost, it is rarely used in bulk machining applications. In specialized CNC machining, gold is used for connectors or micro-parts in aerospace and electronics where performance outweighs cost. Lead offers a cost-effective dense material alternative for non-electrical, non-luxury purposes.
Zinc
Zinc is commonly used in die casting and some CNC machining services due to its malleability and corrosion resistance. It’s about 37% lighter than lead, making it unsuitable for applications requiring dense mass. However, it is easier to machine than lead and often used in decorative or structural components.
Titanium is valued in CNC machining for its high strength-to-weight ratio and biocompatibility. It’s around 60% lighter than lead. While titanium is ideal for aerospace and medical implants, it is not used where density is a critical factor. Lead remains the superior option for weight-based applications such as ballast or shielding.
Silver
Silver comes close to lead in terms of density, being only about 7.5% less dense. It also provides excellent thermal and electrical conductivity, making it valuable in precision CNC machined electronics. However, like gold, silver is costlier than lead. For applications requiring mass without conductive properties, lead is the practical and affordable choice.
Summary Table: Lead vs. Other Metals
| Metal |
Density (g/cm³) |
Compared to Lead |
| Lead |
11.34 | Reference |
| Aluminum |
2.70 | ~76% less dense |
| Iron |
7.87 | ~31% less dense |
| Stainless Steel |
7.90–8.10 | ~28% less dense |
| Copper |
8.96 | ~21% less dense |
| Zinc |
7.14 | ~37% less dense |
| Titanium |
4.51 | ~60% less dense |
| Silver |
10.49 | ~7.5% less dense |
| Gold |
19.32 | ~70% more dense |
Why This Matters in CNC Machining
Selecting the right material isn’t just about strength or cost—it’s also about density, especially when CNC machining parts for use in weight-sensitive, vibration-damping, or radiation-shielding environments. Lead’s high density makes it indispensable for certain niches where other metals simply don’t measure up. CNC machining factories offering both CNC turning and CNC milling services must weigh these factors carefully to deliver the highest-quality custom parts for their clients.
Use the basic formula:
Temperature Effects
Adjust for thermal expansion using:
where β is the thermal expansion coefficient.
Purity and Impurities
Density may shift by up to 0.5–2% if the lead includes impurities or alloying metals.
Alloy Composition
Use weighted average of constituent densities based on volume or mass fractions.
Archimedean Principle
Weigh the object in air and then in water. Use displacement to calculate volume. Suitable for CNC machining parts with simple geometry.
Pycnometer Method
Best for powdered or small samples. Requires lab conditions but provides high accuracy.
X-ray Diffraction
A non-destructive method useful for analyzing internal structures and confirming density without physically altering the CNC part.
Radiation Shielding
Lead's density absorbs X-rays and gamma rays, making it indispensable in medical and nuclear CNC machining applications.
Lead-Acid Batteries
Heavy plates improve energy density. CNC milling ensures uniformity and proper contact.
Sound & Shock Absorption
Lead parts reduce vibrations in heavy machinery, thanks to its mass and damping ability.
Weights and Ballast
Used in aerospace, automotive, and nautical applications where compact mass is vital.
Ammunition & Fishing Sinkers
Lead’s density ensures rapid descent and stable trajectory.
Where Can We Find Lead?
Batteries
The most common modern use. CNC machining ensures plate accuracy.
Paints & Pigments
Though regulated, still used in industrial applications.
Alloys
Blended for soldering, casting, and structural CNC components.
Pipes
Still found in older infrastructure.
Radiation Shielding
Hospitals, labs, and nuclear sites often require custom CNC machining of lead blocks.
These sources highlight the importance of proper handling and machining processes in CNC machining factories.
Proper safety measures must be in place during any CNC machining operation involving lead.
Lead is toxic. CNC machining services handling lead must follow strict environmental and safety protocols, including:
Lead density isn’t just a number—it’s a critical property that influences performance, safety, and machining precision. For CNC machining parts, understanding this density ensures better quality, reduced waste, and optimal design. Whether you’re working with lead for shielding, balance, or damping, knowing how to measure and apply its density is key to machining success.
This section addresses the most common and critical questions related to lead density, its properties, and how they impact CNC machining parts. Whether you're sourcing materials, planning a CNC milling or CNC turning operation, or simply need clarity, these concise answers will help you make better decisions in your CNC machining services.
Is lead the densest metal?
No, lead is not the densest metal. While it is very dense (11.34 g/cm³), osmium (22.59 g/cm³) and iridium (22.56 g/cm³) are denser. However, due to cost and machinability, lead remains one of the most practical high-density materials used in CNC machining.
Is lead density variable?
Yes, lead density can vary slightly due to temperature, pressure, and especially impurities or alloy content. CNC machining factories must consider this during part design and when selecting lead-based materials for high-precision CNC components.
How do I measure the density of lead in my home?
The most accessible method is the Archimedes principle. Weigh the object in air, then in water to find the volume of displaced water. Divide the mass by the volume to get density. While this is not as precise as lab methods, it offers a decent estimation for small-scale testing.
Does lead block radiation simply because of density?
Primarily, yes. Lead's high atomic number and density make it very effective at absorbing and attenuating radiation. This is why lead is widely used in CNC-machined parts for medical and nuclear shielding.
How do I calculate the relative density of lead?
Relative density = Density of Lead / Density of Water.
So, 11.34 g/cm³ ÷ 1 g/cm³ = 11.34.
This means lead is 11.34 times denser than water.
Which element has a density of 11.85 g/cm³?
A material with a density of 11.85 g/cm³ is likely a lead alloy with minor metal additives (such as tin or antimony), or potentially bismuth-based compounds. It could also be a slightly impure form of lead used in specific CNC machining applications.
What is the actual density of lead?
The standard density of pure lead is 11.34 g/cm³, 11,340 kg/m³, or 0.410 lb/in³, at room temperature. This value may slightly vary in alloys or depending on processing conditions in CNC machining factories.
Is lead really that dense?
Yes, lead is extremely dense compared to common industrial metals like aluminum, iron, and even copper. This density is why it’s ideal for CNC machining parts that need weight, vibration damping, or radiation shielding in compact dimensions.
Is lead denser than steel?
Yes, lead is significantly denser than steel.
This means lead is about 44% denser, making it the better choice for mass-driven designs.
Is lead the heaviest of all metals?
Not quite. While it’s among the heaviest commonly used metals, elements like osmium, iridium, and platinum are heavier. Lead, however, is often the most cost-effective dense material available for CNC machining.
Is lead the densest element?
No. Osmium holds the record as the densest naturally occurring element, with a density of 22.59 g/cm³, nearly twice that of lead. Lead is still more widely used in machining because of its affordability and ease of shaping.
What is the density of 13.6 g/cm³?
A density of 13.6 g/cm³ typically refers to mercury, a liquid metal at room temperature. It is not used in CNC machining due to toxicity and handling difficulties, but is referenced for comparison in high-density materials.
What is the density of steel?
Steel density ranges from 7.85 to 8.05 g/cm³, depending on the grade and alloy composition. CNC machining factories must consider this when selecting materials for strength-to-weight ratio optimization.
What is the densest metal?
Osmium is the densest metal, with a density of 22.59 g/cm³. Due to cost and rarity, it's not commonly used in CNC machining. Lead remains a practical alternative for most high-density applications.
What is the density of diamond?
Diamond has a density of 3.51 g/cm³. Although extremely hard, it's much less dense than metals. It’s not used for mass-based CNC parts but often as a coating or cutting tool in CNC milling due to its exceptional hardness.
Who can produce the best steel in the world?
Countries like Japan, Germany, and Sweden are globally recognized for producing high-quality steel, thanks to advanced metallurgy, precision control, and rigorous quality standards. CNC machining factories often source steel from these regions for premium CNC machining services.
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