Wire EDM offset calculator
A 0.30 mm wire with a 0.05 mm spark gap runs 0.200 mm off the part’s edge and leaves a 0.40 mm kerf; to cut a 20 mm punch its centre runs 20.40 mm across. Enter the wire Ø and the spark gap, choose the cut and whether you keep a punch or a die, for the offset, the kerf, the smallest inside corner and the wire’s path across the part.
The drawing shows the wire, the gap and the corners to one scale; the wire table loads any common size into it.
- Wire offset
- Wire offset in inches
- Kerf width
- Smallest inside corner radius
- Wire path across the punch
- Fanuc's gap for a rough cut
- 15–70µm
How it’s calculated
The kerf is d + 2g, and the smallest inside corner radius is the offset. The wire path across a punch is its size + 2o, across a die opening its size − 2o. Here: o = 0.150 + 0.050 = 0.200 mm, kerf 0.400 mm.
| Wire Ø | Sold as | Offset at this gap | Kerf | Inside R after a finish pass |
|---|---|---|---|---|
| 0.10 mm | .004″ | 0.100 mm | 0.200 mm | 0.058 mm |
| 0.15 mm | .006″ | 0.125 mm | 0.250 mm | 0.083 mm |
| 0.20 mm | .008″ | 0.150 mm | 0.300 mm | 0.108 mm |
| 0.25 mm | .010″ | 0.175 mm | 0.350 mm | 0.133 mm |
| 0.30 mm | .012″ | 0.200 mm | 0.400 mm | 0.158 mm |
| 0.33 mm | .013″ | 0.215 mm | 0.430 mm | 0.173 mm |
Why can a wire cut a sharp outside corner but not an inside one?
The spark reaches a full offset all round the wire. Going round an outside corner the wire’s centre swings on an arc and the corner is left sharp; at an inside corner the centre turns sharp, and the part keeps a radius equal to the offset. A thinner wire, or a finish pass with its smaller gap, makes that radius smaller.