CNC Engraving Custom Products: How Depth, Tools and Fixtures Set the Limits

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  What Engraving Actually Removes
• 2
  How Small Can Letters Go Before They Stop Reading
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  Material Choice Changes the Cut, Not Just the Speed
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  Why Fixturing Decides Whether the Mark Lands in Place
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  Where Engraving Cost Comes From
• 6
  Engraving Route Compared With Other Marking Methods

Engraving is a subtractive cut, not a print. A rotating cutter follows a toolpath and removes material along letters, logos, part numbers or textures. The finished mark is the negative space left behind. Because the cut is mechanical, the mark cannot flake off, fade under UV or wash out in a solvent bath the way an ink layer can.

The cut geometry is simple to describe. A ball nose cutter of radius r at depth d leaves a groove whose width follows the toolpath stepover and whose profile follows the ball. A V-bit with included angle a leaves a groove whose width grows with depth: at 0.2 mm deep, a 60° V-bit cuts roughly 0.23 mm wide. Go to 0.4 mm deep and the same tool cuts about 0.46 mm wide. Depth controls width, so you set depth to control stroke weight.

Three numbers decide whether a drawing is machinable. Character height sets the minimum stroke width the cutter can enter. Groove depth sets tool load and cycle time. Wall angle sets how the mark reads under raking light. Change one and the other two move. That coupling is the reason engraving drawings need a process review, not just a dimension callout.

Cutting forces are light compared with milling a pocket. A 0.5 mm ball nose at 0.1 mm depth in 6061 aluminium sees a small radial engagement, so spindle speed can run high and heat stays low. The trade is speed of the toolpath. Fine detail means many short moves, and those moves, not the spindle, set the cycle time.

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  Ball noseWidth comes from stepover; profile is rounded
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  V-bitWidth grows linearly with depth; good for sharp corners
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  Flat end millConstant width; leaves square shoulders and burrs
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  Engraving insertReplaceable tip; used on hard steel and long runs

A stroke narrower than the cutter tip cannot be cut. The tool either skips the stroke or ploughs a groove wider than the drawing asks. In practice, the smallest reliable stroke is about the tip diameter of the smallest cutter you are willing to run. On our machines that is a 0.5 mm ball nose for soft metals, and a 1.0 mm cutter for stainless and tool steel, where a thin tool breaks.

Height follows from stroke. Most fonts need a stroke about one seventh to one tenth of the cap height to stay open at a distance. A 0.5 mm stroke therefore supports roughly 3.5 to 5 mm cap height. Below that, the counters in letters like e, a and g start to close up, and the mark reads as a smudge rather than text.

Marking depth changes the answer. A shallow mark of 0.05 mm is enough to catch light on a bead blasted face, and it can hold finer strokes because the cutter is barely loaded. A deep 0.3 mm groove needs more tool pressure and a sturdier cutter, which pushes the minimum stroke up. Decide the reading distance first, then set depth to match.

Laser marking is a different route on the same part. Our laser marking holds a minimum character height of 1.5 mm and adds no tool load, but it produces a shallow, low-contrast mark that can fade on some anodised colours. When a buyer asks for CNC engraving custom products in a metal housing, the choice between a cut groove and a laser mark is usually about depth and feel, not about resolution.

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  Read at arm's length3 mm cap height with a 0.5 mm stroke
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  Read at 300 mm5–6 mm cap height; 0.8 mm stroke is safer
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  Read under a loupe2 mm cap height max, shallow depth, polished face

Aluminium engraves cleanly. Grades 6061 and 7075 both take a sharp edge, and 7075 holds a crisper wall on thin strokes because it is stiffer. Chips clear well, so a shallow pass at high spindle speed leaves little burr. Anodising after engraving darkens the groove and raises contrast, which is why so many control panels are cut first and anodised clear or black afterwards.

Stainless steel behaves differently. Grades 304 and 316 work harden under a dull tool, so a light pass with a worn cutter can raise the surface hardness and ruin the next pass. Use a fresh cutter, keep the feed per tooth up and avoid dwelling. Grade 303 machines better and is the practical choice when the part is a knob or a plate and corrosion demand allows it.

Copper and brass cut easily but burr heavily. C110 copper tears at the edges and needs a sharp tool plus a light finishing pass. C36000 brass gives the cleanest engraving of the common alloys and is the usual pick for instrument plates. Plastics split into two groups: POM, PMMA and ABS cut cleanly, while PP and HDPE smear and need a different feed and a sharp, polished cutter.

Wood is the least predictable. Grain direction decides whether a stroke tears or shears. Cutting across the grain gives a clean line; cutting along it lifts fibres. A down-cut cutter helps on veneered panels because it pushes the fibres down instead of lifting them. Hardwoods such as maple and walnut hold detail better than softwoods.

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  Best contrast after anodising6061 and 7075 aluminium
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  Best all-round cutC36000 brass
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  Watch work hardening304 and 316 stainless
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  Watch smearingPP, HDPE, soft copper

A groove 0.1 mm deep has no tolerance for part movement. If the blank shifts 0.2 mm between the datum face and the engraving pass, the mark moves with it. On a curved housing, the same shift also changes the local depth, so one end of the text cuts deep and the other end barely scratches. Fixturing is not a secondary concern here. It is the main one.

Flat plates are the easy case. Clamp them on a machined face, probe the top surface, and cut in one pass. The probe step matters: it tells the control where the surface actually sits, so a 0.1 mm plate thickness variation does not become a 0.1 mm depth error.

Curved and cylindrical parts need either a rotary table or a contoured soft jaw. A Ø400 mm rotary table lets us engrave around a cylinder in one setup, keeping the text aligned to the axis. For one-off parts we often cut a soft jaw from POM that matches the outer profile, then clamp the part in it. That jaw costs a little setup time and removes most depth variation.

Thin walls are the hard case. A 0.8 mm wall deflects under even light cutter pressure, and the mark comes out uneven or the wall dents. Support the back of the wall with a matching insert, reduce depth to 0.05 mm, and take two light passes instead of one heavy one. When none of that works, laser marking is the fallback.

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  Flat plateMachine face, probe, single pass
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  CylinderRotary table or contoured soft jaw
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  Thin wallBack support, shallow depth, two passes
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  Freeform surface5-axis toolpath keeps depth normal to the surface

Cost tracks toolpath length, not part size. A large plate with two engraved lines is cheap. A small plate covered in fine texture is not, because the toolpath runs for hours at a small stepover. When a drawing asks for a full-surface texture, ask whether the same visual result can come from a coarser stepover at greater depth. Often it can, and the cycle time drops by half.

Tool life is the second cost driver. A 0.5 mm cutter in aluminium lasts a long time. The same cutter in 316 stainless may need changing mid-run, and every change costs a re-probe and a test cut. Batch the parts so one setup covers as many pieces as possible, and keep stainless engraving on the same machine to avoid re-qualifying the tool offset.

Volume changes the method, not the principle. There is no minimum order quantity here, so a single prototype and a 10,000 part run use the same cutting logic. At higher volume we look at whether a dedicated soft jaw pays for itself, and whether a fixture can hold six parts instead of one. Those choices cut the per-part time without touching the drawing.

Post-processing adds its own step. Anodising, bead blasting or electroless nickel all change how the groove reads. Bead blasting softens edges and lowers contrast. Clear anodising darkens the groove slightly. If the mark must stay legible after finishing, cut it deeper and plan the finish into the drawing from the start.

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  Cheapest markFew strokes, large stepover, one pass
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  Most expensiveFull-surface fine texture on stainless
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  Finish interactionBlasting softens; anodising darkens