Gutters by cut method: router, knife and laser
·5 min read
Gutters are not a styling choice, they are a consequence of the tool. Set them from the cut method and material yield stops being guesswork.
Router: the bit sets the floor
A router removes material. The gutter has to swallow the kerf plus enough shoulder that the vacuum still holds both parts while the bit passes between them. In practice that means a little more than the bit diameter, not exactly the bit diameter.
The working defaults: a 2mm bit takes a 3mm gutter, a 4mm bit takes 6mm, a 6mm bit takes 8mm. Below those figures the offcut between parts turns into a thin rib that lifts into the spindle.
Knife: butt them up
A drag or tangential knife removes nothing, so pieces can share a line. Gutter zero, and on a butted layout the cut serves both neighbours — half the cut length and no waste strip.
The catch is bleed. Butted pieces with 3mm bleed each overlap by 6mm, so either the bleed overhangs into the neighbour deliberately or the layout has to allow for it. Overhanging bleed is fine when the knife cuts on the trim line and the artwork either side is continuous or hidden.
Laser: allow for the burn
A laser kerf is narrow but the heat-affected zone is not. A 2mm gutter keeps scorching off the neighbouring piece's edge on acrylic and keeps the extraction airflow between parts.
When to override
- Thick material: a 10mm acrylic cut with a 6mm bit wants more than 8mm, because the bit deflects.
- Small parts: tiny pieces need either a bigger gutter or holding tabs, or they end up in the extraction.
- Weeding channels: if a kiss-cut channel runs around each part, the gutter has to clear two channel widths plus the bit.
- Guillotine finishing: cut in strips, so the gutter only matters in one axis.
Centre first, then count
Once the gutter is fixed, the imposed block should be centred on the sheet with even margins all round rather than pushed into a corner. Even margins mean the same grip either side, the same distortion either side, and register marks that sit at a repeatable distance from the bed edge.
Centring also makes the yield honest. If a layout only fits because it is jammed against two edges, it does not really fit.
In the suite
Pick the cut method and bit size and the gutter fills itself in from the table above, still editable per job. The imposed block centres on the sheet or roll automatically, and the piece count updates live so you can see the moment a gutter change costs you a row.
Run it on a live job
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