CNC Mill Pricing Guide for Engineers and Buyers

• 1
  What drives a milling quote
• 2
  Which cost driver dominates at which quantity
• 3
  Setup and programming are fixed costs
• 4
  Tolerance and surface finish compound the price
• 5
  Material choice changes machine time, not just stock price
• 6
  Part geometry: pockets, thin walls, and deep cavities
• 7
  Finishing, inspection, and documentation
• 8
  How to compare two milling quotes fairly
• 9
  Step by step: how to get a usable milling quote

Every milling job starts with a fixed block of work that has nothing to do with how many parts you order. The programmer reads your STEP file, decides the setup orientation, writes toolpaths, and picks tools. On a 3-axis part with two simple faces, that block may be an hour. On a 5-axis part with undercuts and a tight profile, it can be several hours before the spindle turns.

Then there is the physical setup. Fixtures, soft jaws, vises, and zero-point plates all take time to build and dial in. A part that needs four separate setups pays that cost four times, and the operator has to re-datum the part at each flip, which introduces stacked position error.

This is why the same part can quote at two very different numbers from two shops. One shop runs a 3-axis machine with three fixtures. Another runs a 5-axis center and machines five faces in a single setup. The second shop charges more per hour but may still come in lower overall once you count fixtures and re-datum time.

• 1
  One setup beats threeConsolidating faces onto a 5-axis or mill-turn center removes re-datum error and fixture cost.
• 2
  Programming is not freeComplex surfacing can take longer to program than to cut on the first part.
• 3
  Fixtures are sometimes billedAsk whether soft jaws or custom fixtures are a one-time charge you keep.

A milling quote is not priced at a single tolerance. It is priced at the tightest tolerance on the drawing. If one bore is ±0.005 mm and the rest of the part is ±0.1 mm, the shop must still control the whole process tightly enough to hold that bore, including thermal growth and tool wear.

Surface finish works the same way. A face at Ra 1.6–3.2 μm comes off the machine as-machined. A face at Ra 0.2–0.8 μm usually needs a separate finishing pass with a smaller stepover, a sharper tool, or a slower feed. That pass adds cycle time and can add a polishing step.

The trap is applying tight tolerances and fine finishes to surfaces that do not need them. Cosmetic faces, clearance holes, and non-mating edges rarely justify ±0.005 mm. Mark only the features that mate, seal, or locate. Everything else can stay at general tolerance and save real money.

• 1
  Tolerance is a process requirementOne tight feature forces tight control everywhere upstream of it.
• 2
  Finish is a separate operationFine finish often means a second pass, not a slower first pass.
• 3
  Use GD&T to say what mattersA datum and a true position callout tell the shop where to spend time.

Engineers often compare material by the price of the bar or plate. That is only part of the cost. Aluminium 6061 cuts fast, holds tolerance well, and lets the shop run aggressive feeds. Titanium Ti-6Al-4V cuts at a fraction of that rate, generates heat at the cutting edge, and wears tools quickly.

Inconel is worse. It work-hardens, pushes cutting forces up, and demands rigid setups and low feed rates. On a part with deep pockets, the cycle time difference between aluminium and Inconel can be three to five times, before you count tool replacement.

There is also availability. Common grades like 6061, 304 stainless, and 1018 steel sit on shelves. Exotic grades may need to be ordered, which adds lead time. If your design allows a switch from 7075 to 6061 on a non-structural bracket, the quote usually drops and the delivery date gets shorter.

• 1
  Cutting speed drives cycle timeAluminium runs several times faster than titanium at the same tool diameter.
• 2
  Tool life is a real line itemInconel and hardened steel consume carbide inserts quickly.
• 3
  Stock form mattersPlate, bar, and near-net forgings leave different amounts of material to remove.

Geometry decides how much metal the tool must remove and how safely it can do it. A shallow pocket with a 10 mm radius is straightforward. A deep pocket with a 2 mm corner radius forces the shop to use a small, long tool. Small tools deflect, so the shop reduces depth of cut and feed, and cycle time climbs.

Thin walls are a separate problem. When the wall gets thinner than about 1 mm on aluminium or 2 mm on steel, cutting forces start to push the wall away from the tool. The shop has to take lighter passes, add support material, or plan the sequence so the wall stays stiff until the last operation.

The practical rule is to keep the cutter as large and as short as the feature allows. Increase internal corner radii, reduce pocket depth-to-width ratios, and add draft or relief where the function permits. These changes often cost nothing in performance and cut a meaningful amount of cycle time.

• 1
  Small corners force small toolsA 2 mm internal radius limits the cutter diameter and the achievable feed.
• 2
  Deep pockets need long reachLong tools deflect more, so the shop slows down to hold tolerance.
• 3
  Thin walls need supportBelow roughly 1 mm in aluminium, expect extra operations or a fixture.

Post-machining work is where quotes diverge most between shops. Anodizing, hardcoat, electroless nickel, powder coating, bead blasting, and laser marking are all separate operations, each with its own setup, racking, and minimum charge. Laser marking has a minimum character height of 1.5 mm, so a very small logo may need a different method.

Inspection is the other half. A general-tolerance bracket may need only a quick check with calipers. A part with ±0.005 mm features and a true position callout needs a CMM program, a first-article report, and in-process checks. That is skilled labor, and it shows up in the quote.

Documentation matters if you are in a regulated industry. Medical device work under ISO 13485 and automotive work under IATF 16949 carry traceability and record-keeping requirements. Aerospace parts often need material certs and a full inspection report. Ask for these up front, because retrofitting documentation after the run is expensive.

• 1
  Finishing has minimum chargesAnodizing a handful of small parts may cost the same as a full rack.
• 2
  Inspection scales with toleranceCMM time and first-article reports are billed labor.
• 3
  Certs drive process controlISO 9001, IATF 16949, ISO 13485, and ISO 27001 each add specific obligations.

Two quotes are only comparable if they cover the same scope. Ask each shop to break the number into material, setup, programming, cycle time, finishing, and inspection. A blended figure hides which stage is expensive, and you cannot negotiate what you cannot see.

Check the assumptions too. Does the quote include material certs, a first-article report, and shipping? Does it assume a single setup or several? Is the lead time counted from PO or from drawing approval? Small differences in scope explain most of the gap between a low quote and a high one.

At GreatLight, quotes come back with a free DFM analysis within 12 hours, and production can start within 24 hours of approval. Parts typically ship in 3–5 days. There is no minimum order quantity, so the same pricing logic applies whether you need one prototype or a 10,000+ part run.

• 1
  Demand line itemsMaterial, setup, cycle, finish, and inspection should be visible.
• 2
  Confirm scope in writingCerts, reports, and shipping are the usual hidden gaps.
• 3
  Ask what was assumedA quote built on a different setup plan is not a lower price, just a different plan.