Compare CNC Milling Turning Companies

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  What to compare before you award the job
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  Machine mix is the first real filter when you compare CNC milling turning companies
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  Why milling and turning together change the result
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  Tolerance, inspection and the paperwork behind them
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  Engineering support separates a vendor from a partner
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  Volume, materials and finishing in one quote

A quote sheet rarely tells you which machine will run your part. Ask instead. A shop with 16 simultaneous 5-axis centers, 16 mill-turn centers and 12 four-axis mills can hold a complex geometry in fewer setups than a shop running only 3-axis verticals. Fewer setups means fewer datum shifts and less stack-up error.

Size matters too. GreatLight runs a 4,000 mm maximum processing size, with travels of 4,000 × 400 × 150 mm on the large frame, 750 × 1,150 × 550 mm and 600 × 600 × 600 mm on the mid frames, and 500 × 500 × 450 mm or 500 × 310 × 200 mm on the compact machines. A Ø400 mm rotary table covers round work that would otherwise need a separate turning setup.

If your part is a shaft with a milled flat, a housing with a bored bore, or a bracket with angled holes, you want milling and turning in the same building. When they are split across two vendors, you own the tolerance stack between them. That is a real cost, and it lands on your desk.

One caution. Big travel numbers do not mean a shop is right for deep pockets or thin walls. Ask what fixture they would use and how they would control chatter. The answer tells you more than the machine list.

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  Ask for the machine, not the categoryWhich model, how many axes, what work envelope.
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  Match travel to part envelopeLeave room for fixture and tool clearance.
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  Prefer one roof for mill-turn partsOne supplier owns the whole tolerance stack.

Milling handles pockets, sculpted surfaces and 3D contours. Turning delivers concentricity, roundness and a tight finish on diameters. Many real parts need both: a turned body with milled ports, or a milled plate with a turned boss. Splitting that across two suppliers adds a second setup, a second datum and a second inspection report.

A mill-turn center or a Swiss-type lathe with live tooling does the turning and the milling in one program. The part stays in one chuck, so the bore and the bolt circle keep their relationship. On a Ø50 mm hub with six milled slots, that is often the difference between holding position and chasing it.

There is a limit. Very large prismatic parts still belong on a 5-axis mill, and long slender shafts still belong on a lathe. A good supplier will tell you which route they would take and why, before you commit to a purchase order.

Material also steers the choice. Aluminum 6061, 7075 and 6082 cut fast on either platform. Stainless 17-4PH and 316L, titanium TC4 and Inconel work-harden, so the shop needs the right inserts, coolant strategy and a spindle with enough rigidity. Ask what feeds and speeds they would start with. Vague answers are a warning.

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  One chuck, one datumConcentric features keep their relationship.
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  Match platform to geometryPrismatic to mill, rotational to turn, mixed to mill-turn.
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  Ask about hard materialsTooling and coolant plan for 17-4PH, TC4, Inconel.

Any shop will print ±0.005 mm on a website. The question is how they prove it. A credible answer names the CMM, the fixture, the temperature and the sampling plan. GreatLight inspects 100% of parts before shipment, covering raw material check, in-process monitoring and final inspection, with reports available on request.

Finish is the other half of the spec. As-machined surfaces land around Ra 1.6–3.2 μm. A high-quality finish sits at Ra 0.8–1.6 μm. Fine finishing reaches Ra 0.2–0.8 μm. If your drawing calls for Ra 0.4 μm on a sealing face, ask whether that is measured or assumed, and whether the quote includes the extra pass.

Certifications act as a gate. ISO 9001:2015 covers general quality systems. IATF 16949:2016 is required for automotive and EV work. ISO 13485:2016 applies to medical devices. ISO 27001:2022 covers information security, which matters when your drawings are the asset.

None of these certificates make a good part by themselves. They tell you the shop has a documented process and gets audited against it. That is worth something when a deviation appears and you need a corrective action, not an apology.

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  Ask how tolerance is verifiedCMM, gauge, sampling plan, report format.
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  Match finish to functionRa 0.8–1.6 μm for most sealing and sliding faces.
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  Check certificates against industryIATF 16949 for auto, ISO 13485 for medical.

The fastest way to compare CNC milling turning companies is to send one real part and watch the reply. A price-only response tells you a sales desk is quoting. A reply with DFM notes, flagged features and an alternative route tells you an engineer read the file.

Useful DFM feedback is specific. It names a corner radius that needs a smaller tool, a wall that will deflect at the current depth of cut, or a tapped hole too close to a shoulder. It also offers a trade: loosen this tolerance and save a setup, or keep it and accept the cost.

Timing signals matter as much as content. GreatLight returns a quotation and free DFM analysis within 12 hours, and production can start within 24 hours. Parts typically ship in 3–5 days. Those numbers only help if the first reply is technically useful, so read the notes before the price.

Confidentiality should be settled early. Uploads are secure and confidential, and an NDA is available on request. For defense-adjacent, medical or unreleased automotive work, sort that out before you send the STEP file, not after.

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  Send a real partA test quote reveals more than a brochure.
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  Read the notes firstSpecific DFM comments signal a real engineering desk.
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  Handle NDA up frontAvailable on request before files move.

Order size should not be a barrier at either end. GreatLight has no minimum order quantity, running from a single prototype to 10,000+ part runs. That matters when you need three units to prove a design and a thousand units six months later from the same program.

Material coverage decides how much you have to split the job. Aluminum grades run from 6061-T6 and 6082 to 7075 and ADC12. Stainless covers 303, 304, 316L, 17-4PH and 440C. Steel includes 1018, 1045, 4130, 4140 and 4340. Copper and brass span C101 to C36000, plus beryllium copper. Titanium and special alloys include TC4 (Ti-6Al-4V), Inconel, and magnesium AZ31B or AZ91D.

Finishing is where quotes often diverge. Anodizing, electroless nickel, zinc, silver and gold plating, powder coating, black oxide, bead blasting, tumbling, brushing, polishing, and laser marking with a minimum character height of 1.5 mm all sit under one supplier here.

Keep the finishing in-house with the machining when the finish affects fit. Anodizing adds a thin build-up on dimension, and hardcoat adds more. If the anodizer is a third party, someone has to own that allowance. Make sure the quote says who.

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  No MOQOne prototype or a 10,000+ run, same program.
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  Broad material listCuts the number of suppliers you have to manage.
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  Own the finish allowanceDecide who adjusts dimensions for coating build-up.