CNC machining technology explained.

CNC machining is a subtractive manufacturing process in which computer-controlled cutting tools remove material from a solid workpiece. It produces accurate functional parts from metals and engineering plastics without requiring a mold.

Three-axis milling moves the cutter along X, Y and Z and suits many prismatic parts. Four-axis machining adds controlled rotation, useful for features around a part. Five-axis machining adds another rotary direction, enabling complex angled surfaces and fewer setups. The simplest suitable process usually offers the best cost.

Turning is normally preferred for round components such as shafts, bushings, pins and threaded cylindrical parts because the workpiece rotates against a cutting tool. Milling is better for flat faces, pockets and irregular geometry. Mill-turn or secondary milling may combine both.

Wire EDM cuts conductive material with an electrically charged wire and is useful for precise profiles, narrow slots and hardened materials. Small Hole EDM creates very small, deep or difficult holes in conductive metals, including start holes for wire cutting. EDM is slower than conventional cutting but creates features that milling may not reach.

Achievable tolerance depends on part size, geometry, material, feature location, setup count and inspection method. General tolerances are more economical; critical dimensions can be held tighter when clearly identified on a drawing. We review each design before confirming tolerance capability.

A 3D model defines nominal geometry but usually does not communicate tolerance, datum, surface roughness, thread class or inspection requirements. A controlled 2D drawing prevents assumptions and tells the machinist which dimensions affect function.

STEP or STP is generally the most reliable neutral 3D format. Parasolid X_T, IGES and native SolidWorks files may also be used. Add a PDF drawing for tolerances, threads and notes. DXF or DWG can support 2D profiles, while compressed ZIP or 7Z files are useful for multi-file projects.

Rotating end mills leave a radius in internal corners. Larger radii allow stronger, faster tools; very small radii require small cutters and slower machining. A practical internal radius should be larger than the cutter radius, and deep pockets benefit from generous corner relief.

Deep narrow pockets require long tools that may vibrate and deflect. Thin walls can distort under cutting force or when unclamped. Increasing wall thickness, reducing depth-to-width ratio, adding corner radii and allowing multiple setups can improve accuracy and reduce cost.

Yes. Internal and external threads can be tapped, thread-milled or turned depending on size and quantity. Clearly specify thread standard, pitch, class, depth and whether a helical insert is required. Thread gauges may be used when the drawing requires them.

Specify roughness only where it affects sealing, sliding, fatigue, appearance or another function. A finer finish normally needs slower cutting or secondary processing and therefore costs more. Unspecified surfaces can use the supplier's standard machined finish.

Inspection may include calipers, micrometers, height gauges, pin or thread gauges and, when appropriate, coordinate measuring equipment. The inspection plan should focus on drawing-defined critical dimensions. Material certificates, dimensional reports or additional documentation should be requested before quotation.

A DFM review identifies features that may be difficult, risky or unnecessarily expensive to machine. Engineers may recommend changing radii, tolerances, hole depth, tool access, stock size or setup strategy while preserving the intended function.