Custom CNC Machining Precision Parts for Every Industry

• 1
  What matters before you send a drawing
• 2
  Which industries use custom CNC machining precision parts
• 3
  Matching the process to the part, not the other way round
• 4
  Tolerances, surface finish and where the money goes
• 5
  Material choices and what each one asks of the process
• 6
  From upload to shipped parts in six steps
• 7
  Choosing a process for common part types

Aerospace housings, brackets and actuator bodies are usually thin-walled and pocketed, so chatter and distortion decide whether the part passes. Our 16 simultaneous 5-axis machining centers hold contoured surfaces in one setup, which keeps datums consistent across the part. Titanium TA1, TA2 and TC4 (Ti-6Al-4V) are routine here, and so are 7075 and 2024 aluminium. The limit is not the machine but the wall thickness: below roughly 0.8 mm on aluminium, workholding becomes the main risk.

Medical devices bring a different set of constraints. Instruments, manifolds and implant trial parts need edge break control, clean surfaces and a documented route from raw material to final inspection. ISO 13485:2016 governs how we run that route. Stainless 316L and 17-4PH (SUS630) dominate, with finishes in the Ra 0.2–0.8 μm band when a sealing face or sliding fit demands it. Every one of those finishes adds a step, so name the surfaces that need it.

Automotive and EV work is volume-driven. A single motor housing or inverter plate may run from one prototype to 10,000+ parts, and the same program has to hold across that range. IATF 16949:2016 shapes the process controls, first-article checks and change management. Aluminium ADC12, 6061-T6 and 6082 cover most housings, while 4140 and 4340 appear on shafts and gears that see load.

Robotics, electronics and industrial machinery sit between those extremes. Joint housings, end-effector plates, heat sinks and fixture bodies are often mixed-material assemblies where the flatness of one face sets the accuracy of everything bolted to it. Electronics work also tends to need shielding features, connector cutouts and laser marking at a minimum character height of 1.5 mm.

Start with the geometry and the batch size. A flat plate with through-holes and a few tapped features is three-axis work, and putting it on a five-axis machine only adds cost. A part with compound angles, sculpted surfaces or features on five faces is the opposite case: every extra setup on a three-axis machine adds a datum shift, and datum shifts are where tolerance stacks go wrong. Our 27 three-axis and 12 four-axis mills exist for the first category.

Turned parts follow a similar split. Shafts, bushings and fittings belong on a lathe, and our 16 mill-turn centers handle parts that need milling after turning without a second fixturing step. That matters on parts where a cross-hole must be true to a turned bore. Beryllium copper, C36000 brass and 303 stainless are common here. Long, slender turned parts are the weak spot: below about Ø6 mm with a 10:1 length-to-diameter ratio, deflection shows up and we will usually suggest a different approach.

Size sets the machine. The largest envelope we run is 4,000 × 400 × 150 mm, and we also work in 750 × 1,150 × 550 mm, 600 × 600 × 600 mm, 500 × 500 × 450 mm and 500 × 310 × 200 mm envelopes, with a Ø400 mm rotary table for round work. If a part sits near the top of an envelope, say so early. Fixture clearance and tool reach, not the travel itself, are usually what limits the cut.

Prototypes and production parts are not the same job. A prototype should prove function and fit, so we may leave a roughing allowance or skip a cosmetic finish. A production part needs a stable program, defined tool life and a repeatable inspection plan. Both start from the same 3D model, but the routing differs. Tell us which one you are buying.

The tightest tolerance we hold in normal production is ±0.005 mm (±0.0002 in), and that number should be reserved for features that genuinely need it. A bore that locates a bearing may need it. A clearance hole for an M4 screw does not. When a drawing calls out a tight tolerance across a whole part, the cost lands in extra setups, slower feeds, more frequent tool changes and a longer inspection cycle.

Surface finish runs on a similar scale. As-machined surfaces sit at Ra 1.6–3.2 μm, a good general-purpose band for brackets, housings and covers. A high-finish cut reaches Ra 0.8–1.6 μm for sealing faces, sliding contacts and visible parts. Fine finishing at Ra 0.2–0.8 μm is used where a seal, a bearing or an optical surface demands it, and it usually needs a separate light-cut pass and a polished tool.

Some features are geometry problems rather than tolerance problems. Sharp internal corners cannot be cut by a round cutter, so a 3 mm end mill leaves a 1.5 mm radius. Deep pockets need tool reach, and reach costs rigidity. Threads smaller than M2, holes with a depth over 10× diameter, and features on the underside of an overhang all raise the risk of a scrap part. Mark them on the drawing so we can quote them honestly.

Finishes change dimensions in small but real ways. Anodizing builds a few micrometres per surface, hardcoat more than a decorative coat, and plating adds its own layer. If a coated part has a tight fit, tell us and we will machine to allow for the coating rather than after it.

Aluminium is the default for prototypes and most enclosures. 6061 and 6061-T6 machine cleanly and take anodizing well. 7075 gives higher strength for structural brackets but is less forgiving of thin sections. 2024 and 5052 suit formed or riveted assemblies, and ADC12 is a die-casting grade that occasionally appears as a machined equivalent.

Stainless covers a wide range. 303 is the easiest to machine and is fine for fittings and bushings. 304 and 316L resist corrosion and are common in medical and food-contact parts, though they work-harden and need steady feeds. 17-4PH (SUS630) can be heat treated to high strength and is a favorite for shafts and valve parts. 440C goes into bearings and wear surfaces.

Steel grades split by purpose. 1018 and 1045 are general-purpose. 4130, 4140 and 4340 carry load in aerospace and automotive parts and are often heat treated after machining, which means leaving stock and planning for distortion. Tool steel appears on dies and wear plates. Titanium TA1, TA2 and TC4 (Ti-6Al-4V) bring low weight and high strength but demand slow speeds, sharp tools and coolant discipline. Inconel is harder again and is quoted only when the application truly needs high-temperature strength.

Plastics behave differently from metals. POM and PA are stable and machine to tight tolerances. PEEK handles heat and chemicals but is expensive and abrasive on tooling. ABS, PC, PMMA and PP are used for covers, guards and prototypes. Carbon fibre reinforced grades are strong but abrasive, and cut edges need care to avoid delamination.