Machining PA66 or Nylon: A Comprehensive Guide

 

Nylon CNC machining shapes materials by removing excess material from a workpiece. In manufacturing, it’s essential for creating parts. PA66 or Nylon is a popular material for machining. This article provides a comprehensive guide.

What is PA66 OR NYLON?

Nylon is a synthetic polymer that is widely used in various industries due to its excellent mechanical properties. PA6 and PA66 are thermoplastic materials that are characterized by their high strength, rigidity, and toughness. In addition, it also has good chemical resistance and can withstand high temperatures. Nylon is widely used in the automotive, aerospace, and electronics industries, among others. There are 2 types of Nylon: PA6 and PA6.6. More specific, The impact resistance of PA6 is better than PA6.6 and solubility resistance is also better. On the other hand, PA6 absorbs more water than PA6.6, as a result, it will dehydrate in warm and dry environments and become brittle.

milling parts in PA66 also called Nylon
CNC machining China

Machining PA66: The Process

Machining PA66 or Nylon requires a good understanding of the material properties and the machining process. The following are the steps involved in machining PA66 or Nylon.

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Step 1: Select the Right Tooling
The first step in machining PA66 or Nylon is to select the right tooling. More specific,  the tooling used for machining PA66 or Nylon should be made of high-speed steel or carbide. in addition, it should also have a sharp cutting edge and be able to withstand high temperatures. The recommended tool angles for machining PA66 or Nylon are between 10 and 15 degrees.
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Step 2: Set the Cutting Parameters
The cutting parameters for machining PA66 or Nylon depend on the material properties, tool material, and the desired surface finish. For carbide tools, recommended cutting speeds are between 180 and 350 m/min (600–1,150 ft/min). For HSS tools, use lower speeds of 60–180 m/min (200–600 ft/min). Feed rates should be between 0.05 and 0.3 mm/rev (0.002–0.012 in/rev), with lighter feeds for finishing and heavier feeds for roughing. The depth of cut should be between 0.2 and 3 mm (0.008–0.120 in), depending on whether you are finishing or roughing.
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Step 3: Fixturing
Fixturing is the process of holding the workpiece securely during the machining process. As a matter of fact, the fixturing used for machining PA66 or Nylon should be designed to provide maximum support and stability. The recommended fixturing methods for machining PA66 or Nylon are clamping and vacuum chucking.
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Step 4: Machining
The machining process for PA66 or Nylon involves cutting the material to the desired shape and size with a milling or turning machine. The cutting process should be carried out with a constant flow of coolant to reduce the heat generated during machining. In addition, the coolant should be water-soluble and compatible with the material.
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Step 5: Finishing
The finishing process for Nylon involves removing any burrs or rough edges on the workpiece. To clarify, the recommended finishing methods for machining PA66 are deburring, sanding, and polishing.

Advantages of Machining PA66

Machining PA66 has several advantages, including:

  • High strength: PA66 withstands heavy loads and stresses effectively.
  • Chemical resistance: It resists various chemicals, including oils, fuels, and solvents.
  • Heat resistance: Nylon maintains its mechanical properties even at high temperatures.
  • Easy machinability: PA66 is easily machined using standard equipment.

 

 

Applications of Machining Nylon

Typical parts made of Nylon are gears, bushings, cable binders, hinges, etc. Machining PA66 is used in a wide range of applications, including:

  • Automotive: The Automotive industry uses to manufacture parts such as gears, bearings, and fuel tanks.
  • Aerospace: The aerospace industry uses PA66 to manufacture parts such as engine components, landing gear, and electrical connectors.
  • Electronics: The electronics business selects Nylon to manufacture parts such as cable ties, connectors, and switches.
  • Industrial: The industry in general likes PA66 to manufacture parts such as rollers, gears, and bearings for heavy-duty machinery
  • Consumer goods: Manufacturers of consumer goods use Nylon to manufacture parts such as kitchen utensils, sporting equipment, and toys.

 

Conclusion: Machining PA66 or Nylon is an important process in the manufacturing industry. In other words, it is essential to select the right tooling, cutting parameters, and fixturing methods to ensure a successful machining process. In addition, Nylon offers several advantages, including high strength, chemical resistance, and heat resistance. As a result, the industry uses it widely in various applications, including automotive, aerospace, electronics, industrial, and consumer goods. If you’re in need of machining PA66, be sure to work with an experienced and reputable machining provider to ensure the highest quality plastic parts.

Cutting Parameters for Machining PA6 and PA66

When machining PA6 (Polyamide 6) and PA66 (Polyamide 66), the recommended cutting speeds, feed rates, and other parameters depend on the operation (milling or turning) and the tool material. Below are general guidelines:

Material Preparation

Before machining, dry the raw stock at 80–90°C for 8–12 hours to bring moisture content below 0.2%. PA6 can absorb up to 2.5% moisture, PA66 up to around 2.0%, and wet material will expand, produce poor surface finish, and make it impossible to hold tolerances. For tight-tolerance work (±0.05 mm or better), anneal the stock at 90–100°C for 2–4 hours followed by slow furnace cooling to relieve internal stresses before machining. For critical parts, consider a second annealing step after roughing and before finishing.

1. Turning PA6 & PA66

Cutting Speed (Vc):

  • HSS Tools: 60–180 m/min
  • Carbide Tools: 180–350 m/min

Feed Rate (f):

  • Roughing: 0.1–0.3 mm/rev
  • Finishing: 0.05–0.15 mm/rev

Depth of Cut (ap):

  • Roughing: 1–3 mm
  • Finishing: 0.2–1 mm

Tool geometry: Use a positive rake angle of 10°–15° with a relief angle of 8°–12°. A nose radius of 0.4–0.8 mm is a good starting point for general work. A larger nose radius improves surface finish but increases cutting forces and may cause deflection on slender parts. Use tools with chip breaker geometry to manage nylon’s tendency to produce long, stringy chips.

2. Milling PA6 & PA66

Cutting Speed (Vc):

  • HSS Tools: 50–150 m/min
  • Carbide Tools: 150–300 m/min

Feed per Tooth (fz):

  • Roughing: 0.1–0.3 mm/tooth
  • Finishing: 0.05–0.15 mm/tooth

Axial Depth of Cut (ap):

  • Roughing: 2–5 mm
  • Finishing: 0.5–2 mm

Radial Depth of Cut (ae):

  • Full slotting: up to 1× tool diameter
  • Side milling: up to 50% of tool diameter for roughing, 10–25% for finishing

Use climb milling rather than conventional milling. It reduces chatter and produces a better surface finish on nylon. Prefer 1- or 2-flute end mills, as fewer flutes give chips more room to evacuate and reduce heat buildup. Sharp, polished carbide end mills work well; uncoated is generally fine for unfilled nylon.

3. Calculating Spindle Speed

To convert cutting speed (Vc) into the RPM you actually set on the machine, use:

n (RPM) = (Vc × 1000) / (π × D)

Where Vc is the cutting speed in m/min and D is the workpiece diameter (turning) or tool diameter (milling) in mm. For example, a 20 mm end mill at 200 m/min gives roughly 3,180 RPM.

4. Troubleshooting Common Problems

  • Material melting or smearing: The feed is too low relative to the speed. The tool is rubbing instead of cutting. Increase the feed rate, reduce the speed, or both. Ensure the tool is sharp; a dull edge generates friction heat instead of shearing cleanly.
  • Stringy or wrapping chips: Increase the feed rate and use compressed air directed at the cutting zone. On turning operations, use a tool with chip breaker geometry.
  • Poor surface finish: Check for tool wear. Reduce the feed rate for the finishing pass. A larger nose radius (turning) or lower stepover (milling) will improve the finish. Make sure the material was dry before machining.
  • Parts warping after machining: Internal stresses are releasing. Anneal the stock before machining. For parts with uneven cross-sections, rough from both sides to balance material removal, then allow the part to rest before finishing.
  • Dimensional drift: Likely caused by moisture re-absorption or thermal expansion during cutting. Machine dry material, use compressed air for cooling rather than liquid coolant, and measure parts at a consistent temperature.

5. Coolant and Lubrication

Dry machining with compressed air is the preferred approach for unfilled nylon. The air clears chips and provides enough cooling without introducing moisture. If additional cooling is needed, use a light mist of water-soluble coolant — but keep it minimal, as nylon absorbs moisture and may swell. Never flood-cool nylon parts.

6. Workholding

Nylon is softer and more flexible than metal, so excessive clamping force will deform the part and cause dimensional errors. Use soft jaws, padded fixtures, or vacuum chucking where possible. Ensure the workpiece is fully supported underneath during milling to prevent deflection.

7. Tolerances

For general machining of unfilled PA6 and PA66, expect to hold ±0.05 mm with proper preparation (dry material, stress-relieved stock, stable temperature). Achieving tolerances of ±0.02 mm is possible but requires pre-dried and annealed material, tight fixturing, and controlled environment. Keep in mind that nylon’s coefficient of thermal expansion is roughly 80–100 × 10⁻⁶/°C, far higher than metals, so parts will change size with temperature. Measure at a consistent temperature.

8. Differences Between PA6 & PA66

PA66 has higher crystallinity, giving it greater stiffness (flexural modulus ~3.0 GPa vs ~2.7 GPa for PA6), better creep resistance, and a higher melting point (~260°C vs ~220°C). This makes PA66 easier to machine cleanly with less tendency to deform under cutting forces, and it’s preferred for precision parts, gears, and high-load applications. However, PA66 tends to have higher residual stress, so annealing before machining is more important.

PA6 has better impact resistance and toughness, making it better suited for snap-fits, shock-absorbing components, and large structural parts. It absorbs more moisture than PA66 (up to 2.5% vs ~2.0%), so pre-drying is especially critical. PA6 is also generally more cost-effective.

For both materials, if the part will be exposed to moisture in service, account for dimensional growth due to moisture absorption when setting your machining tolerances.

Explaining milling versus turning
FAQ — Machining PA66 or Nylon | Davantech

FAQ

Frequently Asked Questions

Common questions about machining PA6 and PA66 Nylon — cutting speeds, feeds, tolerances, and troubleshooting — answered by Davantech's engineering team.

Cutting speeds depend on the tool material and operation. For turning with HSS tools, use 60–180 m/min; with carbide tools, 180–350 m/min. For milling with HSS tools, use 50–150 m/min; with carbide tools, 150–300 m/min. These ranges apply to unfilled PA6 and PA66 — glass-filled grades require lower speeds (around 100–180 m/min) due to their abrasive nature.
For turning, use feed rates of 0.1–0.3 mm/rev for roughing and 0.05–0.15 mm/rev for finishing, with depths of cut of 1–3 mm (roughing) and 0.2–1 mm (finishing). For milling, use 0.1–0.3 mm/tooth for roughing and 0.05–0.15 mm/tooth for finishing, with axial depths of 2–5 mm (roughing) and 0.5–2 mm (finishing). If the material starts melting or smearing, increase the feed — the tool is rubbing instead of cutting.
Yes. PA6 can absorb up to 2.5% moisture and PA66 up to around 2.0%, which causes dimensional expansion, poor surface finish, and difficulty holding tolerances. Dry the raw stock at 80–90°C for 8–12 hours to bring moisture content below 0.2% before machining. For tight-tolerance work (±0.05 mm or better), also anneal the stock at 90–100°C for 2–4 hours with slow furnace cooling to relieve internal stresses.
Dry machining with compressed air is the preferred approach for unfilled Nylon. The air clears chips and provides enough cooling without introducing moisture. If additional cooling is needed, use a light mist of water-soluble coolant — but keep it minimal, as Nylon absorbs moisture and may swell. Never flood-cool Nylon parts.
For general machining of unfilled PA6 and PA66, expect to hold ±0.05 mm with proper preparation — dry material, stress-relieved stock, and stable temperature. Achieving ±0.02 mm is possible but requires pre-dried and annealed material, tight fixturing, and a controlled environment. Nylon's coefficient of thermal expansion is roughly 80–100 × 10⁻⁶/°C, far higher than metals, so parts will change size with temperature. Always measure at a consistent temperature.
This happens when the feed rate is too low relative to the cutting speed — the tool rubs the material instead of cutting it, generating friction heat. Increase the feed rate, reduce the speed, or both. Also check that the tool is sharp; a dull cutting edge generates heat instead of shearing cleanly. Use 1- or 2-flute end mills for milling, as fewer flutes give chips more room to evacuate and reduce heat buildup.
Post-machining warping is caused by internal stresses releasing as material is removed. To prevent this, anneal the stock before machining at 90–100°C for 2–4 hours with slow cooling. For parts with uneven cross-sections, rough from both sides to balance material removal, then allow the part to rest before the finishing pass. For critical parts, consider a second annealing step after roughing and before finishing.
PA66 has higher crystallinity, greater stiffness (flexural modulus ~3.0 GPa vs ~2.7 GPa for PA6), better creep resistance, and a higher melting point (~260°C vs ~220°C). It machines cleanly with less tendency to deform and is preferred for precision parts, gears, and high-load applications. PA6 has better impact resistance and toughness, making it better suited for snap-fits, shock-absorbing components, and large structural parts. PA6 is also generally more cost-effective. PA66 tends to have higher residual stress, so annealing before machining is more important.