What Actually Drives the Price of a Machined Stainless Part

Cost / 21 Sept 2026

Quotes for the same stainless part can differ by a factor of two between competent shops. That is rarely because one is greedy. It is because the drawing left room for interpretation, and each shop priced its own reading.

Understanding where the money actually goes lets you write a drawing that gets consistent quotes, and lets you find savings that do not compromise the part.

The rough proportions

For a typical machined stainless part in moderate quantity:

Element	Share of piece price
Machine time	45 to 60 %
Material	15 to 25 %
Setup, amortised	5 to 20 %, depending on quantity
Tooling consumption	5 to 10 %
Inspection and paperwork	3 to 10 %
Outside processes	0 to 20 %
Deburring, handling, packing	3 to 8 %

The single most useful thing to take from that table: machine time is the big number. Anything that shortens the cycle beats anything that reduces the bar cost.

1. Grade

The largest lever, and the one most often left unexamined.

Grade	Machinability index	Relative cycle
SUS303	78	Fastest
SUS430	54	Fast
SUS304	45	Reference
SUS316 / 316L	36	Roughly 20 to 30 % slower

A turned part moved from SUS304 to SUS303 can approach half the cycle time at a similar bar price. That is the cheapest specification change available on most stainless jobs, and it costs nothing at the drawing stage.

The conditions are real, though. SUS303 cannot be welded and must not go near chlorides. SUS430 cannot be welded easily, is magnetic and is not for wet service. Four questions settle it: is the part ever wet, ever welded, ever cold, ever near something magnetically sensitive? Details in SUS303 vs SUS304 vs SUS316 and SUS430 vs SUS304.

2. Tolerances

The second largest lever, and the easiest to overspecify.

±0.1 mm: free
±0.05 mm: small increase
±0.02 mm: a finishing pass and measured inspection
±0.01 mm: grinding or hard turning, separate operation

The mistake is blanket application. A drawing where every dimension carries ±0.02 mm is priced as though every dimension matters. Tolerance the three or four features that carry function, set the general class to medium, and the price falls without the part changing. The realistic bands are in stainless machining tolerances, and the general tolerance classes in JIS B 0405 and B 0419.

3. Surface finish

Ra 3.2 and 1.6: free, this is what normal machining leaves
Ra 0.8: small, more attention and more frequent tool changes
Ra 0.4: real, usually an additional operation
Ra 0.2 and below: grinding, lapping or electropolishing

The step from 0.8 to 0.4 is where an operation enters. As with tolerances, the failure mode is a general note applying a tight finish to the whole part. Specify the general finish once and the exceptions on the faces that need them. See JIS surface finish symbols.

4. Geometry that forces slow cutting

Several features make a part slow without making it better:

Thin walls. Below about 1 mm the price climbs steeply. See thin wall stainless machining
Deep holes. Over 5 times diameter needs through coolant, over 10 times needs gun drilling. See deep hole drilling and tapping
Sharp internal corners. A 1 mm radius forces a small tool and a slow feed. A 3 mm radius can halve the time in a pocket
Deep narrow pockets. A long tool deflects, deflection means light cuts, and light cuts in stainless work harden
Features on five or six faces. Each additional setup is a fixture, an alignment and a tolerance stack
Excessive thread depth. Engagement beyond about 2 times diameter adds tapping time and tap breakage risk for negligible strength

Each of these is worth a question: is it functional, or is it inherited from a model that was never reviewed?

5. Quantity

Setup is a fixed cost spread across the batch.

1 to 5 pieces: setup and programming dominate. The unit price will look absurd against the material cost, and it is not padding
6 to 50: setup still significant, curve falling steeply
51 to 200: the comfortable middle for most job shops
200 to 1000: dedicated tooling and optimised fixturing become justifiable, unit price drops again
Over 1000: bar fed automatics or dedicated cells, a different class of shop

Give the real quantity in the enquiry. A shop that quotes 500 and receives an order for 5 will requote, upward.

If you expect to reorder, say so. A shop that knows a fixture will be reused prices the first order differently.

6. Paperwork and inspection

Each of these is real hours:

Mill certificate: small
EN 10204 3.1: small, but it narrows which stock the shop can use
First article inspection report: moderate, a one off per revision
Full CMM dimensional report: significant, and per batch if you ask for it per batch
Heat lot traceability and part marking: moderate, and it constrains the whole process

Ask for what the part needs. A 3.1 certificate and a CMM report on a bracket is money spent on documents nobody opens. On a regulated part, the same documents are not optional. See material certificates.

7. Outside processes

Passivation, electropolishing, heat treatment, plating and bead blasting each carry a minimum lot charge and a lead time of their own. On a small batch the minimum charge can exceed the machining.

Passivation is cheap. Electropolishing is several times more, and it removes 10 to 40 micrometres of material that the machining has to allow for. Heat treatment adds a full cycle and a finishing operation after it. See passivation vs electropolishing.

8. Drawing quality

This one does not appear on any cost sheet and it affects every quote.

A drawing with an unclear datum scheme, a missing tolerance class, triangle finish symbols and an ambiguous material note gets quoted with risk priced into it. The shop cannot tell what it is committing to, so it adds margin. A clean drawing gets quoted at cost.

The difference is often larger than any single feature on the part. Running the JIS drawing checklist before the enquiry goes out is the highest return activity on this list.

Where to look first

In order of return per minute spent:

Review the general tolerance class and the blanket surface finish note. Ten minutes, frequently a double digit percentage saving
Ask whether the grade can change. Four yes or no questions about service
Check the thin walls, the deep holes and the small internal radii. Are they functional?
Check the thread depths. Anything beyond 2D is waste
Review the certificate and inspection requirements. Are they specified because a standard requires them, or by habit?
Give the real quantity and say whether it repeats
Fix the drawing before the enquiry, not after the first quote

None of these change what the part does. All of them change what it costs.

Want a second opinion on where the cost sits in your part? Get a quote. An engineer reads it and prices it with the cost drivers named, and if you order we place, manage, inspect and ship the parts on one PO. Within 24 business hours.

Questions

What is the biggest single cost on a machined stainless part?

Machine time, on almost every part. Material is usually 15 to 25 per cent of the piece price. That is why a grade change that halves the cycle time saves more than a cheaper bar ever will.

Why did my quote change so much between two shops?

Usually because they read the drawing differently. The general tolerance class, the surface finish note and the certificate requirement are the three things most often interpreted differently, and each one moves the price.

Does quantity change the price much?

Enormously below about 50 pieces, where setup dominates. Between 50 and a few hundred the curve flattens. Above that, dedicated tooling becomes justifiable and the unit price drops again.

What is the cheapest change I can make?

Relaxing tolerances and surface finish on features that do not need them, then reviewing the grade. Both cost nothing to change on the drawing and both move the price immediately.

Have a drawing for a stainless part?

Send it and an engineer reads the title block, quotes it within 24 business hours, and if you order we place, manage, inspect and ship the parts on one PO and one invoice.

Get a quote