EDM Finish

EDM Finish & EDM Surface Technology

Mastering VDI 3400 Surface Comparison & NDT Reference Standards


EDM Finish Scale VDI 3400 Surface Comparison Pattern

EDM Surface Roughness Conversion Chart

For precision engineering and EDM surface evaluation, understanding the correlation between VDI 3400, Ra (Roughness Average), and Rmax is essential.

VDI 3400 Grade Ra (µm) Ra (µinch) Rmax (µm) EDM Surface Class
VDI 12 0.40 16 1.5 Fine Finish
VDI 18 0.80 32 3.1 Medium Fine
VDI 24 1.60 63 6.3 Medium Texture
VDI 30 3.15 125 12.5 Standard EDM
VDI 36 6.30 250 24.0 Rough Texture
VDI 45 18.0 710 70.0 Extra Rough

Expert EDM Surface Solutions

EDM Finish (Electrical Discharge Machining) is critical for creating NDT (Non-Destructive Testing) reference standards and test blocks. The importance of EDM surface finish lies in its ability to produce consistent, high-precision cavities and blind holes in hardened tool steel.

NDT & Quality Control Applications

Precise EDM surface texture is vital for ultrasonic and eddy current testing. Our standards ensure that your reference blocks have the exact edm finish required for calibrated NDT inspections.

Standard Compliance:

  • VDI 3400 Reference: From VDI 12 to VDI 45 (12-45 grain).
  • SPI Finish Standards: Grades A1, A2, A3 (Mirror) to D1, D2, D3 (Textured).

PURCHASE EDM FINISH SCALES

EDM FINISH REFERENCE PLATES

Approve the texture before steel is cut

Stop approving mold texture from photos. Lock the finish with a physical A–F reference plate before machining, molding, or supplier sign-off.

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Choose the right A–F finish reference plate

Match the reference format to the material, inspection point, and people approving the surface.

A · Metal VDI plaqueDurable shop-floor comparison for EDM texture review and supplier alignment.
B · Plastic VDI plaqueSee how VDI texture reads on molded plastic before appearance approval.
C · Portable metal/plastic VDI scaleCompact reference for supplier visits, incoming inspection, and quick comparison.
D · Transparent-material VDI plaqueReview how texture affects clear and transparent molded parts.
E · Plastic SPI scaleBlack and transparent plastic references for SPI finish appearance checks.
F · 12-piece steel SPI setTactile steel references for practical mold-finish comparison and approval.

VDI 3400 to Ra quick reference

Select a common VDI grade for an approximate engineering reference.


Approx. Ra 3.15 µm / 124.0 µin

Engineering reference only. It is not an official equivalence, calibration result, or acceptance certificate. Put the required finish on the drawing and agree the final measurement and visual-approval method with your customer and supplier.

Need an A–F recommendation?

Tell us the part material, required VDI or SPI range, inspection stage, and destination country. We will help narrow the suitable reference format.

Email your requirement

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