Check Routed PCB Cutout Corners Against the Mating Part

A rectangular cutout drawn with sharp internal corners may not accept a square mating feature after the PCB is routed. A rotating cutter leaves an internal radius. Review that geometry in the mechanical assembly and specify the corners that matter before fabrication.

Compare finished shapes rather than outlines alone

Place the mating part’s maximum material envelope inside the minimum permitted PCB opening. Include its corner shape, positional variation and insertion direction. A nominal width and height comparison can miss interference concentrated at the corners.

Eurocircuits’ routing explanation connects routing-tool diameter with the resulting internal corner radius. Its standard and optional tool sizes describe its services, not every fabricator’s capability. Confirm the applicable tool and finished tolerance with the supplier selected for the board.

Decide whether the corner is functional

If the mating feature is rounded or does not enter the corner region, a normal routed radius may be acceptable. If it needs a sharp clearance envelope, consider a deliberate relief feature or a change to the mating part. Show the intended final geometry rather than leaving an operator to invent a corner treatment.

As a simple geometric example, a 2 mm diameter cutter cannot leave a zero-radius concave corner in an ordinary routed pocket. A 1 mm nominal tool radius explains the interference, but runout, process allowance and dimensional tolerance still belong in the finished-feature review.

Review the cost of a smaller tool

A smaller radius may require a different tool or process and can change manufacturing constraints. Confirm the cutout width, board thickness and access as a combination. Do not request the smallest available tool when a modest change to the mating part or clearance would satisfy the function more robustly.

Check copper clearance around any added relief. A corner hole or dog-bone shape removes material beyond the original rectangular opening. Review every copper layer and nearby mechanical feature, including how the altered corner affects strength and component placement.

Check data and a representative assembly

Use one authoritative finished contour and ensure the fabrication viewer shows the intended radii or reliefs. Do not supply contradictory sharp and rounded versions in different files. The mechanical model used for fit review should match the released contour.

Inspect representative finished cutouts and test the intended insertion and seating process. Record the mating-part revision and tolerance assumptions with the result. Revisit the review after changing supplier, board thickness or enclosure geometry. A successful nominal prototype fit does not establish clearance at the combined dimensional extremes.