- Find the smallest hole in the drawing — Zorocut's pre-cut check flags any hole smaller than the thickness
- Compare it with the laser table below, or with two times the thickness on air plasma
- Tell the customer before you quote: drilled after cutting for a charge, or cut as drawn with no promise on roundness
Fiber laser: minimum hole by thickness
| Thickness | LaserBoost minimum | SendCutSend rule (50 %) | Zorocut warns below |
|---|---|---|---|
| 1 mm | 0.5 mm | 0.5 mm | 1 mm |
| 2 mm | 1.5 mm | 1 mm | 2 mm |
| 3 mm | 2.5 mm | 1.5 mm | 3 mm |
| 5 mm | 3.5 mm | 2.5 mm | 5 mm |
| 6 mm | 4 mm | 3 mm | 6 mm |
| 10 mm | 5.5 mm | 5 mm | 10 mm |
| 12 mm | 6 mm | 6 mm | 12 mm |
| 15 mm | 8.5 mm | 7.5 mm | 15 mm |
LaserBoost cuts on Trumpf lasers; its table covers steel, and for aluminium and copper it asks for holes equal to the thickness, otherwise clearing the scraps out of the holes is the customer's job. SendCutSend's 50 % is a rule of thumb: it finds its limits by cutting smaller and smaller holes until the laser fails to pierce, leaves the cut incomplete or makes a dirty edge, then backs off, and lists the tested value on each material page. Below the minimum, it says, holes distort, char or fail to cut. Zorocut's pre-cut check is stricter on purpose: it warns about any hole smaller than the thickness.
Why small holes fail
- The pierce is wider than the kerf — SheetCAM has a setting for exactly that — and the lead-in needs room inside the hole. In a tiny hole the crater and the lead-in overlap the finished edge.
- Heat: SendCutSend compares the narrow areas between cuts to a fuse — too little material absorbs too much energy, and it burns or warps.
- Taper: the beam spends longer at the top of the sheet than at the bottom, so cut edges lean slightly (SendCutSend), and more so in thick material.
- Slugs: in aluminium and copper below LaserBoost's minimums, the cut-out pieces may stay in the holes.
Plasma: one to two times the thickness
Plasma holes taper and pick up a ding where the cut starts and ends; Hypertherm names both as the problems of plasma hole cutting. Its True Hole process — XPR and HPRXD high-definition systems, mild steel up to 25 mm, applied by ProNest, EDGE Connect or an approved CAM — covers holes from 2:1 down to 1:1 diameter to thickness, possibly 0.5:1 on some machines. In Kinetic's example every hole under 21 mm in 10 mm plate gets True Hole with a semicircle lead-in, and larger holes are cut the normal way. A Hypertherm customer story reports that 1/2 in holes in 1/4 in mild steel (2:1) take a bolt. On air plasma, such as a Powermax, there is no published minimum: treat two times the thickness as the smallest bolt hole you promise and drill anything smaller (our rule of thumb).
What to tell the customer
- Put the limit in the quote: holes under a stated size in this thickness are drilled after cutting.
- Offer the choice: cut as drawn with no promise on roundness or straightness, or drilled to size for a charge.
- For tapped holes, cut them undersize or mark the position and drill to the tap-drill size, so the thread does not depend on the cut.
- Price drilled holes as a second operation, not as pierces — and a cut hole as a pierce plus a lead, see pierce time.
Sources
- LaserBoost, Design guide for flat laser-cut parts (minimum holes, bridges, micro-joints)
- SendCutSend, Sheet cutting guidelines (minimum hole size, common-nested parts)
- SendCutSend, EDU[CAD]TION study guide 5.2: Design parts that pass DFM
- SendCutSend, EDU[CAD]TION study guide 5.1: Design around cutting processes
- Hypertherm, About True Hole technology
- Hypertherm, Plasma hole cutting
- Kinetic PrimeCut help, Hypertherm True Hole
- SheetCam TNG Setup and Operation Manual v3.1.17
- Hypertherm, Powermax45 XP/65/85/105 Cut Charts Guide 811300MU (cartridge, Duramax torches)
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