Deburring internal holes and slots in laser-cut sheet metal is possible when the abrasive tool can reach the opening and the workpiece stays securely supported. A belt-and-rotary-brush process can remove raised burrs and soften accessible hole and slot edges. It is not a universal solution for deep bore walls, blind holes or very narrow openings. The right acceptance test checks every specified edge—not just the outside profile.
Can a machine leave internal holes and slots clean?
Start by defining what “clean” means on the drawing. Removing a protruding burr, breaking a sharp edge, creating a specified radius and removing oxide from a cut wall are different requirements. A part may have a smooth outer perimeter while a slot still contains a burr, or a rounded hole entrance while oxide remains farther down the wall.
For flat sheet metal, a rotary brush deburring machine can work on accessible inner contours as well as the outer profile. Results depend on the opening geometry, sheet thickness, burr condition, brush construction, tool settings and workholding. Where raised burrs need pre-grinding, an abrasive belt may precede the brush stage. The brush must then make effective contact with the relevant edge. Neither additional pressure nor another pass automatically solves an access problem.
Hole edges are not the same as bore walls
A through-hole has an edge on each face and a wall between them. Processing one face does not prove that the opposite edge has been deburred. A narrow slot also has long side edges and tighter ends that need separate inspection. Deep bores, intersecting passages and blind-hole interiors may require dedicated tools or a different process.
Before requesting a machine trial, mark which surfaces need attention: the upper hole rim, lower rim, slot ends, cut walls or all of these. This prevents a sample that looks finished from being accepted against the wrong requirement.
Why burrs remain inside an otherwise finished part
- Limited tool access. A narrow opening or a thick section can restrict contact. The outer edge may receive effective brushing while an internal feature does not.
- Burr condition. A raised, firmly attached burr may need removal before the rounding stage. Brushing alone is not always the right starting point.
- Uneven contact or support. Part movement, distortion and unsuitable settings can make the result inconsistent across the same workpiece.
- Only one face was processed. A burr on the opposite face can remain even when the visible hole entrance looks smooth.
For an overview of the processing stages, use the deburring machine configuration comparison. The configuration should follow the condition of the incoming part and the required outgoing edge, rather than the number of machine stations alone.
Choosing between edge rounding and combined deburring
If the part has already been deburred and the requirement is to soften accessible sharp edges, an edge rounding machine may be the appropriate starting point for testing. Where raised burrs and sharp edges occur together, consider a combined deburring and edge rounding machine.
A grinding belt and a rotary brush do different jobs. Belt processing addresses protruding material on the processed face; brushing can reach accessible contours and soften edges. Whether BR, BBR or BRB is suitable depends on the incoming burrs, surface requirements and trial results. A larger configuration should not be presented as a guarantee that a smaller hole can be processed.
Workholding matters on perforated and complex-shaped parts
A plate with many openings does not behave like a solid rectangle of the same outside dimensions. Cutouts reduce the available support and can affect vacuum holding. Magnetic workholding depends on the material’s magnetic response. Thin webs and projecting tabs also need attention because secure overall holding does not necessarily prevent local deflection.
Provide the complete drawing, not only the outside length and width. For more detail on holding options, see magnetic versus vacuum conveyors. During a trial, include the least stable representative part rather than only the easiest sample.
How to test internal-hole and slot deburring
- Agree on acceptance criteria. Specify burr removal, edge break or radius, dimensional tolerances and surface appearance. Identify both faces wherever both require processing.
- Choose representative samples. Include the narrowest slots, smallest relevant openings, tightest internal contours and typical worst burrs from normal production.
- Record the process. Note the tool configuration, abrasives, settings, feed speed, orientation and number of passes. Include any turning or separate finishing operation.
- Inspect the difficult areas. Use suitable lighting, magnification and measuring methods for the drawing requirement. Inspect slot ends and both hole entrances; do not rely on a general photograph or a bare-finger check.
- Check dimensions and repeatability. Confirm that holes and slots remain within tolerance, then process several representative parts. An attractive first sample does not establish a stable production process.
Photograph the same marked features before and after processing at a comparable angle and scale. If an edge still fails inspection, determine whether the cause is access, burr removal, holding or settings before increasing processing intensity.
What to send Lasvio for a configuration review
Lasvio manufactures sheet metal deburring and edge-rounding machines. For internal holes and slots, the useful starting information is the material, thickness, full part drawing, burr photographs, required edge condition and expected batch size. Include any restrictions on surface marks or dimensional change.
The BR, BBR and BRB range provides configuration options for combined deburring and edge rounding. A sample review should establish whether the required internal edges are accessible, how the part will be held and whether additional processing is necessary. No universal minimum hole or slot size is claimed here because the complete geometry and processing requirements matter.
Send Lasvio your drawing and sample requirements, highlighting the internal features that currently need manual rework. Ask for close-up inspection of those locations, not only a video of the part passing through the machine.
Frequently asked questions
Can a rotary brush deburr internal holes?
It can process accessible hole edges in suitable flat parts. That does not mean it can finish the entire wall of every hole. Access, burr condition and the specified edge requirement must be checked in a trial.
What is the minimum slot width a machine can process?
There is no single value that applies to every machine and workpiece. Slot width, sheet thickness, tool geometry, burrs and the required finish all affect the result. Request a test using the actual slot geometry.
Will one pass remove burrs from both sides of a hole?
Not necessarily. A single-sided process should not be assumed to treat the opposite face. Confirm whether turning the part, another pass or a double-sided process is needed.
Does hole deburring remove oxide from the cut wall?
Not automatically. Burr removal and edge rounding do not prove complete oxide removal. If the wall must be oxide-free, make that a separate requirement and inspect it separately.
Can deburring change hole or slot dimensions?
Abrasive processing removes material and changes the edge. Features with close tolerances require dimensional checks before and after the trial, using methods appropriate to the drawing.
Can thin parts with many cutouts be processed?
They may be suitable if they can be held and supported reliably. The opening pattern, unsupported sections and material influence the setup. Test the actual part rather than assuming that outside dimensions alone establish suitability.