Cheap CNC Machining Service: Where the Cost Actually Comes From

A machined part price is not a mystery number. It is machining time multiplied by the shop rate, plus setup, material, finishing and inspection. When a quote comes back low, at least one of those lines is lower than the others. Knowing which one tells you whether the saving is real or borrowed from somewhere else.

Machining time is usually the largest line. It depends on how much metal the tool has to remove, how many tools the part needs, and how many times the part is re-fixtured. A part that needs three setups costs more than the same part machined from two sides. A pocket that is 12 mm deep and 6 mm wide forces a small tool at low feed, and that single feature can double cycle time on an otherwise simple block.

Setup is charged once per operation, not once per part. On a run of 500 pieces the setup is spread thin. On a single prototype it is the dominant cost. This is why the same geometry quoted at quantity 1 and quantity 200 can differ by a factor of five without anyone being dishonest.

Material is priced per kilogram plus a cut charge, and it is the line buyers underestimate most. A 7075 aluminium block costs several times what 6061 costs, and titanium or Inconel can multiply it again. Switching from a stainless grade to 6061 on a non-critical bracket is often the single largest saving available.

Finishing and inspection are the last two lines. Anodizing, plating, powder coating and polishing are priced per part and per batch, and they add handling between operations. Inspection is where a cheap quote usually goes quiet. We inspect 100% of parts before shipment, with raw material checks, in-process monitoring and a final report on request. A supplier that skips that step is not cheaper. They have simply moved the risk to your incoming inspection.

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  Machining timeRemoval volume, tool count, number of setups.
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  SetupCharged per operation, so it shrinks with batch size.
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  MaterialGrade and stock size drive the price more than most buyers expect.
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  Finishing and inspectionPriced per part and per batch; never free.

Most of the money in a machined part is decided before the quote is sent. Tolerances are the first lever. Calling out ±0.005 mm across a whole drawing forces slow finishing passes, extra gauging and sometimes a second machine. Reserve the tight tolerance for the features that actually locate or seal. A bolt clearance hole does not need it.

Depth-to-diameter ratio is the second lever. A pocket or slot with a depth more than about three times its width requires a long, thin tool that must run slower to avoid chatter. Widening a 6 mm slot to 8 mm can cut cycle time by a third with no functional loss. If the slot is a cable route or a clearance channel, nobody will notice.

Corner radii matter as much as depth. An internal corner called out at R0.5 mm in a 20 mm deep pocket means a 1 mm cutter. Relax it to R2 mm and a 4 mm cutter does the job at several times the feed rate. Add the radius in the model rather than leaving a sharp corner for the machinist to interpret.

Finally, think about how the part will be held. Datum surfaces that are flat, parallel and accessible let us machine more faces in one setup. Parts that must be flipped three times accumulate position error and cost. If you can accept a small tab or a soft-jaw mark on a non-cosmetic face, say so on the drawing. It removes a whole operation.

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  ToleranceApply ±0.005 mm only where function requires it.
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  Depth ratioKeep pockets under 3× tool diameter where possible.
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  Corner radiiRelax R0.5 mm to R2 mm to allow larger cutters.
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  FixturingFlat, accessible datums reduce the number of setups.

Aluminium is the default for cheap machined parts and for good reason. 6061 and 6061-T6 machine fast, hold tolerance well and accept most finishes. 2024 and 7075 are stronger but gummier and more prone to movement after roughing, so they cost more in time as well as stock. 5052 and 5083 are for formed or welded assemblies rather than tight-tolerance machining.

Stainless grades split into free-machining and the rest. 303 and 430 cut cleanly and are the cheap end. 304 and 316 are tougher, work-harden if the tool dwells, and need slower feeds. 17-4PH adds heat treatment and a second setup if you need the H900 condition. If corrosion resistance is the requirement and strength is not, 303 is usually the lower-cost answer.

Steels such as 1018, 1045 and 4140 are inexpensive per kilogram but slow to cut compared with aluminium. Tool steel and 4340 push both material and cycle time up. Titanium TA2 and TC4 (Ti-6Al-4V) and Inconel are the expensive end of the list. They are justified when temperature, weight or corrosion demands it, not when a cheaper alloy will pass the same test.

Plastics sit in a different cost band. POM and ABS machine quickly and are forgiving. PEEK and carbon fibre are expensive as stock and abrasive on tooling, so expect both a higher material line and a higher machining line. For a non-structural cover, ABS or PC will usually do the same job for less.

Process choice follows the same logic. Three-axis milling covers most prismatic parts. When a part has features on five faces, or needs a single-setup datum for position accuracy, a 5-axis machine removes setups and fixture error. That is a cost trade, not an upgrade for its own sake. For round parts with milled flats, a mill-turn center does the work in one cycle instead of two.

Quantities below about 50 pieces rarely justify a casting or a mold. Above a few hundred, die casting or injection molding can beat machining on unit price, but they add tooling cost and lead time. We quote both routes when the quantity is in that overlap so you can compare the real total, not just the piece price.

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  Cheapest to machine6061-T6, 303 stainless, brass C36000, POM.
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  Mid band7075, 304, 17-4PH, 4140, PC and PMMA.
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  Expensive to machineInconel, TC4 titanium, PEEK, carbon fibre.
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  Process switch5-axis or mill-turn only when it removes setups.

There are jobs where chasing the lowest piece price costs more overall. The clearest case is a part with a functional surface that also carries a tight tolerance and a fine finish. If you need Ra 0.2–0.8 μm on a sealing face at ±0.005 mm, that is a deliberate, slow operation. A quote that ignores it will produce parts that leak or fail assembly.

The second case is a run where a defect found late is expensive. Medical and automotive parts carry documentation, traceability and process control that a bare-bones shop does not have. We hold ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022 for exactly these programs. If your part needs that paperwork, price it as part of the part.

The third case is a part that will be revised many times. Prototypes change, and a supplier who quoted from a single drawing without reviewing manufacturability will re-quote every revision. We return a free DFM analysis with every quotation within 12 hours, which usually surfaces the expensive features before the first chip is cut.

A cheap price with no inspection plan is not a saving. It is an unknown. Ask what is measured, on what equipment, and whether the report ships with the parts. If the answer is vague, the price is not comparable to a quote that includes inspection.

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  Fine finish plus tight toleranceBoth operations are slow by design.
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  Regulated programsTraceability and process control are part of the cost.
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  High revision countDFM review up front prevents repeat quoting.
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  No inspection planThe risk moves to your incoming inspection.

Our capacity is built around removing setups and idle time. We run 127 high-precision CNC machines across three wholly-owned plants, including 16 simultaneous 5-axis machining centers, 16 mill-turn centers, 12 four-axis mills and 27 three-axis machines. Maximum processing size is 4,000 mm, with common travels of 750 × 1,150 × 550 mm, 600 × 600 × 600 mm and 500 × 500 × 450 mm, plus a Ø400 mm rotary table.

Having the right machine for the part is where the cost comes from. A long shaft goes on a machine with the travel to hold it in one setup. A complex housing goes on 5-axis so five faces are cut without re-fixturing. A turned part with cross holes goes on a mill-turn center. Matching the part to the machine avoids the two most common hidden costs: extra setups and rework.

Quotation is fast on purpose. You get a price and a free DFM analysis within 12 hours, and production can start within 24 hours after approval. Standard parts ship in 3–5 days. Our historical late-delivery probability is below 2%, which matters because a late part is expensive no matter what the unit price was.

We work with no minimum order quantity, from one prototype to runs of 10,000 or more. Materials cover aluminium 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075 and ADC12; stainless 303, 304, 316, 316L, 420, 430, 431, 440C and 17-4PH; steels 1018, 1045, 4130, 4140, 4340, A36 and tool steel; copper and brass including C101, C110, C27400, C28000 and C36000; titanium TA1, TA2 and TC4, plus Inconel and magnesium AZ31B and AZ91D; and plastics ABS, PC, PMMA, POM, PA, PEEK, PP, HDPE and carbon fibre.

Finishing is in-house so parts do not travel between vendors and lose time or dimensional control. Options include anodizing in clear, colour, hardcoat and conductive grades, electroless nickel, zinc, silver and gold plating, powder coating, black oxide, bead blasting, tumbling, brushing and polishing, plus laser marking with a minimum character height of 1.5 mm.

Tolerance and inspection are the part of the offer we do not trade away. We hold ±0.005 mm (±0.0002 in) where the drawing calls for it, with finishes from Ra 0.2–0.8 μm to Ra 1.6–3.2 μm as machined, and a 99.99% qualification rate. Uploads stay secure and confidential, and we sign an NDA on request.

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  Machine fit5-axis and mill-turn remove setups, which removes cost.
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  TurnaroundQuote and DFM in 12 hours; parts ship in 3–5 days.
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  QuantityNo MOQ, from one part to 10,000+.
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  ConfidentialitySecure uploads; NDA available on request.