Why small holes are a problem
Every hole starts with a pierce, and the pierce and the first millimetres of cut put heat into a small area. In a small hole in thick sheet the edge gets rough and the hole loses its shape. Xometry writes that features smaller than the thickness are still possible, but the quality of the hole and its accuracy will be poor.
The rules differ because machines, gases and quality expectations differ, and not every rule is a laser rule: Protolabs' guideline covers sheet metal fabrication in general, Bystronic's is for its mix-gas cutting. Where a hole is below its rule, a shop may cut it with a lower quality, drill it or refuse it.
CutMeter's check reports tiny contours, those under 0.5 × 0.5 mm, in any thickness. It does not compare holes with your thickness: use the table below or your shop's own rule.
What each source says
Protolabs' sheet metal design guidelines: holes and slots should be a minimum of material thickness in diameter.
Xometry's sheet cutting page: holes and cutouts should be larger than the material thickness or 0.050 in, whichever is greater.
Tolery: the recommended minimum hole diameter is the material thickness × 0.7; the same for webs and slots.
MEILLER's tolerance guide: minimum hole diameter = 0.7 × sheet thickness as a common rule of thumb, so a 7 mm hole in 10 mm sheet.
SendCutSend's sheet cutting guidelines: on the laser, holes and cutouts at least 50% of the material thickness; the exact minimum for each material and thickness is on that material's page.
Bystronic's mix-gas FAQ, word for word: «Up to 15 mm, we guarantee 0,5x material thickness above 0,7x material thickness. But obviously, we are able to make a 2 mm hole in 30 mm.» We read it as 0.5 × up to 15 mm and 0.7 × above.
The rules side by side
| Source | Rule | 1 mm | 3 mm | 6 mm | 10 mm | 20 mm |
|---|---|---|---|---|---|---|
| Protolabs (sheet metal) | ≥ 1 × t | 1 mm | 3 mm | 6 mm | 10 mm | 20 mm |
| Xometry (sheet cutting) | > t, at least 0.050 in (1.27 mm) | 1.27 mm | 3 mm | 6 mm | 10 mm | 20 mm |
| Tolery (recommended) | 0.7 × t | 0.7 mm | 2.1 mm | 4.2 mm | 7 mm | 14 mm |
| MEILLER (rule of thumb) | 0.7 × t | 0.7 mm | 2.1 mm | 4.2 mm | 7 mm | 14 mm |
| SendCutSend (laser) | ≥ 0.5 × t | 0.5 mm | 1.5 mm | 3 mm | 5 mm | 10 mm |
| Bystronic (mix-gas cutting) | 0.5 × t up to 15 mm, 0.7 × t above | 0.5 mm | 1.5 mm | 3 mm | 5 mm | 14 mm |
Questions
What is the usual rule for the smallest laser-cut hole?
A hole at least as large as the sheet is thick is the safe rule most shops accept. Some shops cut down to 0.7 × or 0.5 × thickness; ask before you design below 1 ×.
Is there a lower limit in thin sheet?
Yes, the rules have floors. Xometry asks for at least 0.050 in (1.27 mm) whatever the thickness, and SendCutSend writes that no geometry should ever be smaller than 0.015 in (0.38 mm). CutMeter reports contours under 0.5 × 0.5 mm as tiny.
Do the same rules apply to slots and webs?
Usually similar ones: Tolery applies 0.7 × thickness to webs and slots too, and Protolabs names holes and slots together. Xometry also gives distances from hole to edge and between holes.
What if my hole must be smaller?
Ask the shop: it may cut it with a lower quality, drill it afterwards or refuse it. MEILLER, for example, shows such a hole as a marking or drills it, and cuts a through hole below 0.7 × thickness only when the order says so explicitly.
Does CutMeter check hole sizes?
It reports tiny contours under 0.5 × 0.5 mm in any thickness, and measures every hole's contour. It does not apply a thickness rule, because shops use different ones.
Sources
- Protolabs: Sheet Metal Fabrication Design Guidelines protolabs.com
- Xometry: Custom Sheet Cutting Service xometry.com
- Xometry: Laser Cutting and Designing: Guidelines, Rules, and Safety Tips xometry.com
- Tolery: Découpe laser en ligne (French) tolery.io
- MEILLER: Ratgeber zu Lasertoleranzen (German) meiller-lasertechnik.de
- SendCutSend: Sheet Cutting Guidelines sendcutsend.com
- Bystronic: Laser mix gas, FAQ bystronic.com