The one-to-one rule for small holes is a guideline, not a law
Cutting a hole smaller than the material thickness is difficult because melt cannot escape. Pulsed piercing and process tuning move the limit further than most shops try.
The familiar guideline is that a laser-cut hole should be at least as large in diameter as the material is thick. Below that ratio, quality falls off: the hole becomes tapered, dross accumulates, and the entry may not clear at all.
Why the limit exists
Cutting a hole means the beam traverses a small closed contour. Molten material must be expelled downward through the kerf, and in a small hole the assist gas has very little room to work. The gas jet is roughly the diameter of the nozzle, considerably larger than the hole, so much of the flow is deflected around rather than through it.
Meanwhile, the pierce that starts the hole deposits significant energy in a small area, and heat accumulates because there is nowhere for it to go.
What extends the limit
Pulsed piercing. Reducing pierce energy and extending its duration limits the molten crater and the heat accumulated before cutting begins.
Reduced power during the contour. Cutting the small circle at lower power and speed than the surrounding profile prevents overheating.
Nozzle selection. A smaller nozzle concentrates gas flow, which helps at the cost of more frequent changes.
Beam shaping. Where adjustable ring mode is available, a higher core fraction narrows the kerf, which helps small features specifically.
Sequencing. Cutting small holes when the surrounding material is cool, rather than immediately after adjacent cuts, avoids compounding heat.
The honest limit
With attention, shops routinely cut holes at ratios well below one to one in thin material — down to perhaps half the thickness in mild steel with good process control. Below that, quality degrades in ways that no parameter fixes, and mechanical punching or drilling becomes the right answer.
Why it matters
Designers who apply the one-to-one rule mechanically sometimes redesign parts to avoid small holes that the machine could actually produce. Conversely, designers who ignore the constraint entirely specify features that will scrap parts.
The useful practice is for the shop to characterise its own limit on its own machine and material mix, and to give design a real number rather than a rule of thumb inherited from a handbook.
This article was produced by the LasersNews AI desk and reviewed by our editors.
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