Knob
Is a knob usually a turned part or a milled part?
Geometry decides the process. Rotationally symmetric knobs are commonly turned on a lathe or turning center, while complex profiles, pockets, flats, or decorative surfaces require milling or live-tool machining to produce the final shape in one setup.
Why are knobs often knurled or chamfered?
Knurling improves grip for the operator, while chamfers remove sharp edges and improve handling and perceived quality. CNC shops and knob projects call out these features specifically because they affect both function and feel.
What tolerances matter most on a machined knob?
The critical dimensions are the bore diameter, shaft interface, concentricity or runout, and any threaded or set-screw features. Industrial examples quote extremely tight control, including 0.001-inch precision and sub-hundredth-millimeter tolerance ranges.
In manufacturing, a knob is a manually operated component used for positioning, adjustment, clamping, indexing, or machine control. It is commonly CNC-machined from aluminum, brass, or steel to hold consistent dimensions and tactile feel. In CNC work, the term also refers to the machined part itself, such as a control knob, jog knob, shift knob, or door-hardware knob.
In a typical job-shop run, cylindrical knob bodies start as bar stock on a turning center, where the bore, outside form, and knurled grip are generated in one setup. Live tooling then mills set-screw flats or cross-holes without a second operation. If the knob is sculpted rather than round, the CAM program roughs the blank on a mill, leaves a small support stub for fixturing, and finishes with a ball end mill before the stub is filed off by hand. Throughout this work, the bore and shaft interface control everything: a brass door-knob project can demand 0.001-inch precision, and commercial knob suppliers quote size limits of a few micrometers. After deburring and chamfering, the operator checks the knob on its mating shaft to confirm there is no wobble, binding, or interference.
Bore or shaft mismatch: A bore cut a few tenths oversize or a misplaced set-screw hole lets the knob wobble, bind, or slip on the shaft, leaving a control that fails fit-up and feels loose in operation.
Sharp corners from skipped edge breaks: Omitting chamfers or radii leaves burrs and harsh edges that make the knob uncomfortable to handle and can interfere with assembly, producing a rejected finish.
Inadequate support stub strategy: Poor cleanup of the remaining support material leaves a visible nub, forces rework, or allows the part to shift during deburring and scratch the finished surface when clamped without protection.