CNC Lathe Factory Service: 7 Checks Before You Order

• 1
  Key takeaways
• 2
  Turning capability at a glance
• 3
  Turning length and spindle capacity decide the shortlist
• 4
  What ±0.005 mm actually covers on a turned part
• 5
  Live tooling, mill-turn and the second-operation trap
• 6
  Materials, finishes and what changes the quote
• 7
  Inspection, documentation and certifications
• 8
  MOQ, scheduling and how the quote is built
• 9
  How to send a turning RFQ that gets a usable quote

The first question is not price. It is whether the shop can hold your part at all. A shaft that finishes at 900 mm needs a lathe with enough bed and a steady rest to control deflection at the middle. Below roughly 600 mm, almost any turning shop can quote. Above 1,200 mm the list shrinks fast, and above 2,000 mm you are down to a handful of factories with long-bed machines.

Measure the part as it is held, not as it is drawn. A 700 mm shaft held in a chuck with 150 mm inside the jaws has only 550 mm of unsupported length, so a mid-size lathe may still do it. Add a tailstock or steady rest and the same lathe reaches much further. This is why two shops give you two different answers on the same drawing.

Our turning cells run up to 4,000 mm on the long-bed side and 500–750 mm on the compact side, with a Ø400 mm rotary table for mill-turn work. Send the drawing and we will tell you which cell it lands in. If your part is over 4,000 mm, we will say so instead of quoting and hoping.

• 1
  Under 600 mmAny competent shop. Compete on finish, lead time and reports.
• 2
  600–1,200 mmCheck bed length and steady rest availability before you compare price.
• 3
  Over 2,000 mmFewer vendors. Ask for a deflection plan, not just a tolerance number.

A tolerance printed on a quote means little without scope. ±0.005 mm on a 20 mm diameter bearing seat is a normal, repeatable result on a good lathe with the right insert and a temperature-stable shop. The same figure on a 900 mm shaft is a different job: thermal growth along the part can eat the whole band before the tool finishes the pass.

The practical question is which features carry the tight callout and how the shop proves them. Diameters are usually easier than lengths. Lengths stack from a face, and every chucking variation moves that face. A shop that turns both ends in one setup or uses a probe on the machine holds length much better than one that flips the part twice.

Surface finish travels with tolerance. A 0.005 mm bore with a Ra 3.2 μm wall will not seal. When the drawing calls for Ra 0.8–1.6 μm, plan on a finishing pass with a small nose radius and a slower feed, or a grind after turning. Ask which one is in the quote.

• 1
  Diameters before lengthsTight diameters are routine; tight stacked lengths need probing or single-setup work.
• 2
  Finish is a separate costRa 0.2–0.8 μm usually means grinding or fine turning, not a standard pass.
• 3
  Temperature mattersOn long parts, a warm shop moves the number more than the tool does.

A pure lathe makes round features. The moment your part needs a cross hole, a flat, a slot or an off-axis port, someone has to break the setup. That is where cost and error creep in: a second machine, a fixture, a new datum, and a fresh stack of tolerance.

Mill-turn centers remove that step. The part stays in one chuck, the tool rotates, and the cross feature comes off the same datum as the bore. For hydraulic manifolds, motor shafts and sensor housings, this is often the difference between a clean print and a stack-up argument. We run 16 mill-turn centers for exactly this reason.

Not every part earns mill-turn. If the off-axis work is one hole with a loose tolerance, a drilled second op is cheaper. Mill-turn pays when there are three or more cross features, when their position ties back to a turned bore, or when the part is hard to re-chuck without marking. Decide by feature count and datum chain, not by machine type.

• 1
  One cross featureSecond operation is usually cheaper. Keep it simple.
• 2
  Three or more cross featuresMill-turn wins on position and on handling damage.
• 3
  Tight position to a boreSingle setup removes the datum transfer entirely.

Turning aluminum 6061 and turning 17-4PH stainless are not the same purchase. Aluminum runs fast with sharp edges and generous speeds. Stainless work-hardens, so a light pass with a dull insert glazes the surface and ruins the next cut. Titanium TC4 and Inconel move the problem further: heat stays in the tool, and cycle time can triple against the same geometry in steel.

Tell the shop the temper, not just the alloy. 6061-T6 cuts differently from 6061-O. 316L and 303 both machine, but 303 is free-cutting and 316L is not, which shows up in your price. If the drawing says stainless with no grade, expect a clarification email or a padded quote.

Finishing is the second half of the cost. Anodizing, electroless nickel, black oxide, bead blasting and laser marking are all standard add-ons, but each one has its own lead time and its own masking rules. Marking needs a minimum character height of 1.5 mm to stay legible. Put the finish callout on the drawing before you ask for a price.

• 1
  Name the temperT6, O and H14 behave differently on the same lathe.
• 2
  Free-cutting grades303 stainless and C36000 brass quote lower than 316L and beryllium copper.
• 3
  Finish drives lead timePlating and anodizing add a vendor step outside the turning cell.

Ask what ships in the box. A responsible shop sends material certificates, in-process records for critical features, and a final inspection report with actual measured values, not just a pass stamp. If your incoming inspection is short, that packet is what keeps you from re-measuring every part.

Certifications narrow the field in regulated industries. ISO 9001 covers general quality systems. IATF 16949 is what automotive programs expect, ISO 13485 covers medical devices, and ISO 27001 covers how your drawings and CAD files are protected. A shop holding all four can serve several of your programs without a second audit cycle.

Beware of a certificate that does not match the site doing the work. Ask whether the turning cell that will run your parts is inside the audited scope. We run three wholly-owned plants and can name the site on the quote, which matters when your customer audits the chain.

• 1
  Material certsTraceable heat numbers for the bar stock actually used.
• 2
  In-process dataCritical diameters measured during the run, not only at the end.
• 3
  Scope questionConfirm the certificate covers the plant that will machine your part.

A minimum order quantity is really a statement about how a factory schedules. A shop that runs one prototype on Monday and a 10,000-part lot on Tuesday has tooling, fixtures and inspection set up to absorb small jobs. A shop built for volume will quote your prototype high to discourage it, or add a setup line that doubles the piece price.

Read the quote structure, not the total. Ask what is setup, what is piece price, what is tooling, and what is inspection. A clear breakdown lets you see which quantity breaks the setup cost. If a quote is one lump sum with no tiers, you cannot plan a pilot run and a production run from the same vendor.

Lead time belongs in the same conversation. Quotation and DFM analysis within 12 hours, production start inside 24 hours, and parts shipping in 3–5 days are realistic numbers for a turning job with stock material and a standard finish. If your part needs an exotic alloy or a plating step, add time and say so on the RFQ.

• 1
  No MOQ from one to 10,000+Prototype and production from the same process and the same inspection.
• 2
  Ask for tiersThree quantity columns expose the setup cost and the real piece price.
• 3
  Flag the finish earlyPlating and anodizing sit outside the turning lead time.