Mastering CNC · Knowledge & glossary
Sawing, engraving, swarf milling, nesting, surface finishing …
From our workshop: 12 milling strategies and machining methods, clearly explained and illustrated with manufacturing photographs.
Click an image to enlarge.
Contours are machined in a plane, for example when cutting an outline from a sheet. The cutter diameter limits the smallest internal radius.
The first photograph shows milling with a tracing aggregate in our workshop.
Pockets, holes and contours are machined at defined depths. Small holding tabs can keep cut-out parts attached to the sheet until machining is complete, then are removed.
Holding tabs keep individual parts secured within the sheet during machining. They are removed and finished afterwards. Ramp or helical entries help suitable tools reach the required cutting depth.
Free-form surfaces are machined along three-dimensional toolpaths. Roughing removes bulk material; finishing brings the surface closer to the intended geometry and quality. In surface finishing passes, the cutter follows closely spaced paths across the surface, building up the intended three-dimensional form. Examples from our workshop include a mirror frame machined from deep-routing MDF and a Viking-style bed headboard.
Free profile shaping with surface toolpaths: the profile is built up from many individual machining passes instead of a fixed profile cutter. This allows curved paths and custom profiles for historic components.
The gallery includes a Venetian mask in Swiss stone pine during three-axis machining, alongside custom profile shaping through closely spaced milling passes. Further photographs show different examples of our 3D machining. One example is Freialtar Fahrenberg: we scanned the 70-year-old original and recreated it in oak. The digital twin is retained for future manufacturing.
A rotary axis complements the three linear axes. Depending on the machine design, it orients the tool or the workpiece. It can be positioned or move during machining. These photographs show examples on curved workpieces.
The tool is tilted to the required angle before a machining operation. Its orientation stays fixed during that operation and can then be indexed to another position. This allows openings and surfaces to be machined from different directions without reclamping the workpiece each time.
Two additional rotary or tilting axes allow different tool orientations. In indexed machining the orientation stays fixed during cutting; simultaneous machining allows it to change along the toolpath. Swarf milling uses the side of the cutter to machine a suitable surface, with tool orientation following the geometry.
One application is a plywood pressing form: its machined geometry guides the component during subsequent pressing. Contour, counter-form and workholding are coordinated with the component.
Nesting arranges parts on a sheet to reduce waste while respecting grain direction, clearances and workholding. Transformations repeat a machining operation at defined offsets or angles.
Nesting arranges different contours on the stock to minimise waste. Transforming repeats a source operation at a defined offset. Grain direction, tool clearance and holding points also influence the best arrangement.
V-shaped tools produce lettering and ornaments of varying width by changing cutting depth. Lifting the tool creates pointed surface details. Vertical inside corners in through-cut parts remain limited by the cutter radius.
Engraving can also be applied to curved free-form surfaces. The pointed corners typical of V-carving result from the sloped cut in depth. This differs from a through-cut contour with vertical walls, where the rotating tool limits the internal corner radius.
Fluting consists of lengthwise concave grooves, for example on columns. CNC machining also supports twisting paths and individual profiles, subject to tool access and workholding.
Fluting structures columns and other components with lengthwise grooves. Alongside straight grooves, twisted forms can be machined. Individual profiles can also be made, for example to complement historic components in restoration work. Profile shape, mitres and connectors are considered together.
Internal and external threads can be made in suitable woods and plastics. Dimensions, loading and material determine whether a threaded connection is appropriate.
Internal and external threads, left- and right-hand threads and different pitches can be milled depending on material and dimensions. Metal-free connections in wooden furniture are one application. Strength and fit must suit the intended use.
Suitable sanding tools allow workpiece edges and curved free-form surfaces to be machined under CNC control. The images show sanding drums and discs in use in our workshop. Further finishing depends on the shape, material and required surface quality.
CNC-controlled sawing enables precisely positioned incisions and separating cuts. The saw blade can also be used for shaping. The examples show parallel cuts, notching, cutting tenon shoulders and shaping bases for an artwork. Notching removes a defined section of the workpiece; shoulder cuts define the transition to the tenon.
This happens too: the expanded gallery includes manual rough cutting with a chainsaw directly on a workpiece clamped on the CNC machine. Hands-on craft and digital manufacturing complement each other.
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