Machining Pricing Guide for Engineers

• 1
  Key takeaways
• 2
  What a supplier should state before you compare prices
• 3
  The six cost drivers inside a machining price
• 4
  Why tighter tolerances raise the price non-linearly
• 5
  How axis count and part size change the number
• 6
  What to verify before you accept a low quote
• 7
  Quoting speed versus production speed
• 8
  Step by step: getting a quote you can compare

A machining quote is built from a small number of lines, and most of them are decided by the drawing, not by the supplier. Material is the easiest to see and often the least important. Spindle time, setup, programming, inspection and finishing usually account for the rest. If a quote surprises you, it is nearly always one of those.

Start with material. A 6061-T6 aluminium bracket and a Ti-6Al-4V version of the same bracket are not the same job. Titanium and Inconel cut slower, wear tools faster and need more cautious feeds and speeds. The part price can differ by several times before any machining strategy changes. Pick the cheapest grade that meets the load, corrosion and temperature requirement, and say so on the drawing.

Then look at geometry. Deep pockets, thin walls, long reach features and tight internal radii all force smaller tools and slower passes. A wall 0.8 mm thick in aluminium is workable with care, but it needs light finishing passes and often a support strategy. Square internal corners are a common request and a common cost adder. A corner radius at least equal to the tool radius usually removes the need for EDM or a second operation.

Finally, remember that quantity changes the shape of the price, not just its size. A single prototype pays for programming, fixturing and setup in full. At 10,000 parts those costs are almost invisible. The per-part curve is steep at the start and flat later. That is why a prototype quote tells you very little about the production price.

• 1
  Material gradeAluminium 6061 machines fast; titanium TC4 and Inconel are slow and tool-hungry.
• 2
  Feature countEach hole, pocket and thread adds a tool change and a measured feature.
• 3
  Tolerance classApply tight limits only to mating surfaces, not to the whole part.
• 4
  Order quantitySetup and programming amortise across the run size.

General machining tolerance and precision tolerance are different products. A part held to a general tolerance can be checked with calipers and a bench micrometer. A part held to ±0.005 mm needs a temperature-stable environment, a CMM or a vision system, and often a slower finishing pass on the critical features. The cost is not just the extra cutting time; it is the inspection time and the scrap risk.

Surface finish behaves the same way. As-machined aluminium at Ra 1.6–3.2 μm comes straight off a sharp cutter. Ra 0.8–1.6 μm needs a controlled finishing pass. Ra 0.2–0.8 μm may need polishing or a dedicated finish operation, and it is much harder to hold on a large, thin part. Specify finish only on the surfaces that seal, slide or carry an optical function.

There is a practical trap here. When a drawing states a blanket tight tolerance across every dimension, the shop must assume the worst case for all of them. It will quote for slow passes and full inspection on features that were never critical. A short tolerance table on the drawing, with datums and only the key dimensions called out, often cuts the quote by a noticeable margin.

Inspection should be agreed before the run, not after. We inspect 100% of parts before shipment and can supply reports showing raw material check, in-process monitoring and final inspection. If your application needs a first article inspection report or a specific sampling plan, say that at the quoting stage so the cost is visible.

• 1
  General vs precisionMark only mating, sealing and locating surfaces as precision.
• 2
  Finish by functionRa 0.8–1.6 μm for sealing faces; leave cosmetic areas as machined.
• 3
  Report scopeFirst article, sampling or full inspection should be named on the quote.

Axis count is a cost decision, not a quality label. A part with features on three faces can usually be done on a 3-axis machine with two setups. The same part on a 5-axis machine may finish in one setup, which removes a second fixture, a second datum transfer and the positional error that comes with it. For low quantities the 5-axis route often wins overall even at a higher hourly rate.

The reverse is also true. If a part is a simple plate with through holes, a 5-axis machine adds nothing. It ties up a more expensive spindle on work a 3-axis machine handles at the same tolerance. When you send drawings out for quotation, the useful question is not 'can you do 5-axis' but 'how many setups does this part need'.

Size matters as much as complexity. We machine up to 4,000 mm maximum processing size, with large travels up to 4,000 × 400 × 150 mm and medium envelopes such as 750 × 1,150 × 550 mm. A long part that fits one envelope can be a different job in a smaller one, because the shop has to reposition it mid-cycle. That repositioning adds time, risk and often an extra inspection step.

Rotary work is a separate line too. A Ø400 mm rotary table handles cylindrical and indexed features without refixturing, which suits pump bodies, valve parts and round housings. If your part is mostly round with a few milled flats, mill-turn work on one of our 16 mill-turn centres is usually cheaper than milling a round part from a block.

• 1
  3-axisBest for prismatic parts with reachable features in two setups.
• 2
  4-axisAdds indexing for holes and slots around a cylindrical body.
• 3
  5-axisOne-setup machining for contoured, multi-face or deep features.
• 4
  Mill-turnRound parts with milled features finished without refixturing.

A low quote is only useful if it survives the run. Three things separate a real price from a placeholder: the supplier's own capacity, the certification it actually holds, and the way it handles changes. A shop that subcontracts the finishing step cannot control the finish date, and that is usually where a promised lead time breaks.

Certifications tell you which markets the shop already serves. ISO 9001:2015 covers general quality management. IATF 16949:2016 is the automotive standard and implies traced processes and change control. ISO 13485:2016 applies to medical device work. ISO 27001:2022 covers information security, which matters if your CAD files are sensitive. Ask for the certificate scope, not just the logo.

Capacity is the second check. We run 127 high-precision CNC machines across three wholly-owned plants covering 7,600 m², including 16 simultaneous 5-axis machining centres, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centres. That mix matters because a shop with only 3-axis capacity will quote your contoured part as a multi-setup job whether or not that is the best route.

The third check is change handling. Engineering changes after the first article are normal. What matters is whether the supplier re-quotes openly or absorbs the change and quietly drops the inspection scope. Agree in writing what triggers a re-quote, and ask for the revision number to appear on the quote and on the inspection report.

• 1
  Certificate scopeCheck the standard and the processes it covers, not the badge alone.
• 2
  In-house finishingOne supplier for machining and finishing removes a handoff risk.
• 3
  Change rulesWritten re-quote triggers prevent silent scope cuts later.

Lead time in machining has two parts that are often mixed together. The first is quoting and DFM review. The second is production and shipping. A supplier can be fast at one and slow at the other, so ask for both dates separately. We return a quotation and a free DFM analysis within 12 hours, and production can start within 24 hours once the order and drawing revision are confirmed.

Parts typically ship in 3–5 days for standard work. That figure assumes the material is in stock and the drawing does not change after release. Hard-to-source grades, large forgings and multi-step finishing extend it, and a supplier should say so at the quoting stage rather than after the order. Our historical late-delivery probability is below 2%, which comes from quoting realistic dates rather than optimistic ones.

There is a trade-off worth naming. If you push a shop to compress the schedule, the first thing that gets cut is usually the finishing and inspection buffer, not the machining. That is the wrong place to save time on a sealing face or a bearing bore. If the schedule is tight, reduce scope instead: ship the critical parts first and finish the cosmetic ones in a second batch.

For prototypes, speed usually matters more than unit price. No minimum order quantity means a single prototype is a normal job for us, from one part to runs of 10,000 or more. Use the prototype to lock the design, then re-quote the production volume with the same supplier so the setup knowledge carries over.

• 1
  Quote dateAsk when the quotation and DFM notes will arrive.
• 2
  Start dateConfirm when the spindle actually starts, not when the PO is acknowledged.
• 3
  Ship dateTie it to a drawing revision and a material lot.