Kerf guide
Laser Cut Gasket SVG Generator: Kerf Offset & Materials
A laser beam, a waterjet stream or a drag knife removes a thin strip of material — the kerf. If the cut path runs on the nominal line, the outside of the gasket comes out half a kerf too small and every hole half a kerf too big, so bolts rattle and the seal starts closer to the edge than designed.
The kerf SVG from the gasket DXF generator fixes that: the outer path moves out by your kerf offset and every hole and bore moves in by the same amount, so the part measures true after cutting.
Kerf offset
Outer path out, holes in
Enter half the kerf width; the SVG already carries it.
With a 0.15 mm offset, the ASME 4-inch gasket's Ø19.05 bolt holes are cut on Ø18.75 paths and the Ø114.30 bore on Ø114.00; the outside path becomes Ø228.90. The DXF stays at nominal size for CAD and quoting, and notes the offset on its DIMENSIONS layer.
Methods
Kerf by cutting method
| Cutting method | Typical kerf width | Kerf offset to enter (half the kerf) | Good for |
|---|---|---|---|
| CO2 laser (40–100 W) | 0.10–0.30 mm | 0.05–0.15 mm | Rubber, silicone, fiber sheet; never PTFE, FKM or PVC |
| Fiber laser | 0.03–0.10 mm | 0.02–0.05 mm | Copper and thin metal shims |
| Cricut Maker / drag knife | ≈ 0.00 mm | 0.00–0.05 mm | Soft sheet up to 2.4 mm (Knife Blade) |
| Waterjet (pure water) | 0.10–0.25 mm | 0.05–0.12 mm | Rubber, PTFE, fiber, cork |
| Waterjet (abrasive) | 0.80–1.10 mm | 0.40–0.55 mm | Copper, steel shims, thick laminates |
Measure your own kerf with a 20 mm square
- Cut a test squareDraw a 20.00 mm square with no offset and cut it from the real sheet at your real settings.
- Measure the squareUse calipers on both axes; say it measures 19.80 mm.
- Halve the loss20.00 − 19.80 = 0.20 mm total kerf, so the offset is 0.10 mm.
- Enter and keep itType 0.10 in Kerf offset; note it per material and thickness.
Materials
Seven gasket materials and their laser safety
Several common gasket sheets must never go in a CO2 laser.
| Material | Temperature | Oil / fuel / media | Sheet | CO2 laser | Cricut / knife | Waterjet | Starting kerf offset |
|---|---|---|---|---|---|---|---|
| Nitrile NBR | −30 to +100 °C (−22 to +212 °F) | Excellent: engine oil, fuel, grease, water | 0.8–6.0 mm | Yes, with fume extraction (rubber smoke) | Cricut Maker Knife Blade up to 2.4 mm | Pure water | CO2 0.08–0.12 · knife 0.00 · waterjet 0.05–0.10 |
| Viton FKM | −20 to +200 °C (−4 to +392 °F) | Excellent: fuel, oil, many acids | 0.5–6.0 mm | NO — burning fluoroelastomer releases hydrogen fluoride | Yes (knife / die) | Pure water | knife 0.00 · waterjet 0.05–0.10 |
| PTFE | −200 to +260 °C (−328 to +500 °F) | Inert to almost all chemicals; creeps under bolt load | 0.5–3.0 mm | NO — toxic fluorinated fumes | Yes, up to 1.5 mm | Pure water | knife 0.00 · waterjet 0.05–0.10 |
| Aramid non-asbestos (CNAF) | −40 to +250 °C typical (grade dependent) | Good: water, steam, oil, fuel | 0.4–3.0 mm | Possible, chars edges and smokes binder — knife preferred | Thin sheet (≤ 0.8 mm) with Knife Blade; test first | Pure water | CO2 0.10–0.15 · knife 0.00 · waterjet 0.05–0.10 |
| Silicone VMQ | −60 to +200 °C (−76 to +392 °F) | Poor with fuel and mineral oil; good water, air, food | 0.5–6.0 mm | Yes, leaves white silica ash — wipe edges | Yes (rotary or knife blade) | Pure water | CO2 0.08–0.12 · knife 0.00 |
| Annealed copper | to ~500 °C+ (exhaust, head, banjo) | Exhaust gas, coolant, oil, fuel | 0.3–2.0 mm | NO — reflective; use a fiber laser or abrasive waterjet | Only foil ≤ 0.3 mm (hollow punch + shears) | Abrasive | fiber 0.03–0.05 · abrasive waterjet 0.40–0.55 |
| TPU 95A (3D printed) | −30 to +80 °C (softens above ~80 °C) | Good: oil, grease, water; fair: fuel | 1.0–10.0 mm printed | NO — not a laser material (isocyanate fumes) | n/a — print it | n/a | print: 0.00 (tune flow instead) |
PTFE, Viton FKM, TPU and copper never go in a CO2 laser: fluoropolymers and TPU release toxic fumes, copper reflects the beam. Kerf values are half-kerf offsets in mm — measure your own machine with a 20 mm test square.
Viton FKM releases hydrogen fluoride when burned, PTFE gives off toxic fluorinated fumes and TPU releases isocyanates; cut them with a knife, die or waterjet. Copper reflects a CO2 beam back into the optics, so use a fiber laser or abrasive waterjet. Nitrile and silicone cut on a CO2 laser with good extraction.
Import
Importing the SVG at true size
The SVG root carries width and height in millimetres (or inches) with a matching viewBox, so it imports 1:1. In LightBurn use File › Import and check that the size field reads the gasket size; in RDWorks import the SVG and confirm the dimensions; in Cricut Design Space upload it and keep the size as uploaded.
Cut order matters: the INNER_BORE and BOLT_HOLES groups are blue and cut first while the sheet is still held; OUTER_CUT is red and cut last. For waterjet CAM, import the SVG or the DXF and assign lead-ins on the inner contours first.
Hole positions to check against the drawing come from the bolt circle calculator; the layer list is explained on the parametric gasket CAD generator page.