Prepared from parser behavior, machining-file examples and visual checks performed in CNC Viewer. Always confirm the result against the CAM setup and machine documentation before production.
Woodworking operations
Horizontal holes and edge drilling in CNC previews
A horizontal hole is defined by more than an X and Y point. Its entry face, axis direction, center height, diameter and drilling depth must agree before a side bore can be shown as real removed volume.
The entry face establishes the coordinate plane
Top drilling uses the panel face as its working plane, but an edge operation starts on the front, back, left or right side. Coordinates that look identical can therefore describe different physical locations. MPR and HOP families may store this through a surface code, a side identifier, an angle or a transformation established by an earlier block.
The viewer must transform the local operation into stock coordinates only once. Applying both an explicit edge transformation and a second inferred rotation can mirror the bore or place several holes on top of one another.
Center height and depth control the bore
For a left-edge hole, one coordinate normally locates the bore along the panel length and another gives its height through the stock thickness. Drilling depth then extends inward from the left face. A 30 mm depth on a 600 mm-wide panel is not a through-hole; it is a blind side bore extending 30 mm into the material.
If center height is absent, a format may imply the middle of the panel or refer to a machine variable. That fallback should be visible to the user because an assumed center can look plausible while being wrong for dowels drilled close to a surface.
- Correct entry edge
- Axis points into the stock
- Center remains within stock thickness
- Depth starts at the selected face
Why a side hole can appear as a black mark
A circular mark on an edge usually means the operation was drawn as an overlay but was not subtracted from the solid geometry. This can happen when the renderer supports only vertical height-map removal, when the bore axis is reversed, or when the cylinder stops exactly at the surface and never intersects the stock volume.
A useful check is to hide the toolpath and inspect the model from the opposite side. A valid blind bore has a visible opening and an internal end; a through-bore has openings on both affected faces. Lighting and material color should reveal that depth without relying on a black decal.
Distinguish duplicates from coaxial machining
Some woodworking programs repeat the same operation in a macro expansion or reference table. Other programs intentionally drill from both sides along the same axis. The first case should be deduplicated for statistics; the second represents two physical operations and may leave a meeting point inside the stock.
Compare face, direction, diameter, depth and source record before merging. Coordinates alone are not enough. Preserving the source line or operation identifier in diagnostics makes it possible to explain why apparently overlapping holes remain separate.