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What is FR-4 (Glass Epoxy)? CNC Machining

CNC Machining

FR-4 is a high-pressure thermoset glass-epoxy laminate with a good strength-to-weight ratio and near-zero water absorption. Through our UK CNC machining service, FR-4 (Glass Epoxy) CNC parts can be produced as one-off prototypes or repeat batches.

It is most commonly used as an electrical insulator with considerable mechanical strength, retaining its properties in both dry and humid conditions. Typical uses include automotive applications, electrical insulation and PCBs. Its quoted tensile strength of around 415 MPa gives a useful guide when sizing parts.

Parts are CNC milled or turned and available in green, yellow or black. Upload your CAD file for a quick quote on CNC machining FR-4 (Glass Epoxy), with delivery anywhere in the UK. Finish options (as machined) can be confirmed when you order.

Material

FR-4 (Glass Epoxy)

Description

Strengths

Lead time 10 business days. Strong glass-epoxy laminate with excellent insulation and very low moisture uptake.

Weaknesses

Abrasive dust when machined

Colour & Finishes

Green / yellow / black

Mechanical properties

Ultimate tensile strength

415 MPa

Yield strength

Not specified

Modulus of elasticity

24 GPa

Elongation at break

Not specified

Physical properties

Density

1.85 g/cm³

Hardness

110 HRM

Water absorption

< 0.10%

UK equivalent

Thermal properties

Maximum service temperature

140°C

Thermal expansion coefficient

Not specified

Thermal conductivity

0.29–0.34 W/(m·°C)

Electrical properties

Dielectric breakdown

> 50 kV

Post treatments

Post-processing

Deburring

Recommended finish

As machined

Common applications

Automotive applications

Electrical insulation

PCBs

Fixtures & test jigs

Values shown are typical supplier figures for FR-4 (Glass Epoxy) and may vary with stock condition. Please confirm critical properties before production.

Frequently asked questions

Is FR4 easy to CNC machine?

FR4 machines accurately, but it is abrasive glass-epoxy laminate and produces fine dust, so it needs suitable tooling and extraction.

What tolerances can be held on FR4 parts?

As a rigid thermoset, it holds its shape well, but edges can chip or fray, so sharp corners and very thin sections need care. Achievable tolerances depend on part size, geometry and features, so mark any critical tolerances on a 2D drawing with your upload and they will be reviewed and confirmed in your quote.

What finishes are available for FR4?

FR4 is usually supplied as machined and deburred.

What is FR4 used for?

Typical uses include electrical insulation, PCB-related parts, fixtures and test jigs, and automotive applications.

Should I choose FR4 or Bakelite?

FR4 offers higher strength, excellent insulation and very low moisture uptake. Bakelite is a rigid insulating thermoset that is easier to machine but more brittle.

How long does it take to make FR4 parts?

The typical lead time shown for FR4 is 10 business days from an approved order. Quantity, finishing and any heat treatment can affect this, and your quote confirms the date before you order.

FR-4 CNC Machining