Get a stainless steel CNC processing quote

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  What a stainless steel CNC processing quote is really pricing
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  Grade selection and how it moves the stainless steel CNC processing quote
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  Which features add the most cost to a stainless steel CNC processing quote
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  Quantity, setup and why one part costs more than ten
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  What to send so the quote comes back accurate
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  How 5-axis work changes the stainless steel CNC processing quote
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  Grade and feature choices that move a stainless steel CNC processing quote

Stainless steel does not cut like aluminium. It work hardens: once a tool rubs instead of shearing, the surface under the cut gets harder, and the next pass wears the insert faster than the first. That single property explains most of the price gap.

Heat stays near the edge. Aluminium pulls heat into the chip and the part, stainless steel keeps it at the tip, so cutting speeds drop. On a 304 part we may run 60-90 m/min with carbide where the same shape in 6061 runs 300 m/min or more.

Lower speed means more spindle hours per part. Add shorter tool life and more frequent offsets, and the labor and tooling share of the quote rises while the raw material share stays roughly the same.

So the number you receive is not a material price with a markup. It is cycle time, tool changes, inspection time and risk. That is why two shops can quote the same drawing 40% apart and both be honest.

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  Work hardeningRubbing hardens the surface and shortens insert life.
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  Heat concentrationHeat stays at the cutting edge instead of leaving with the chip.
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  Lower surface speedRoughly one third of the aluminium speed for the same shape.
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  More spindle hoursCycle time per part rises even when the geometry is simple.

The grade you name on the drawing sets the baseline. 303 is the free-machining austenitic grade. It contains sulfur, breaks chips cleanly and machines at the highest speed of the common stainless family. If a part does not need welding or heavy corrosion resistance, 303 is usually the cheapest route.

304 and 316L are the workhorses. They are tougher, gummier and prone to built-up edge. 316L adds molybdenum for chloride resistance, and it is slightly worse to machine than 304. Expect longer cycle times and a higher tooling cost line on the quote.

420, 431 and 440C are martensitic. They machine reasonably well in the annealed state and can be hardened afterwards. Quoting them correctly means knowing the final hardness, because a 50 HRC part is ground or EDM after heat treat, not milled.

17-4PH (SUS630) sits in the middle. In condition H1025 or H1075 it is strong and still machinable with carbide, but it needs a different finishing strategy than the austenitic grades. Tell us the condition, not just the name.

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  Chip control303 breaks chips; 304 and 316L tend to string.
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  Corrosion needOnly pay for 316L when chlorides are actually present.
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  Post-heat-treatHardened martensitic parts need grinding or EDM, not milling.
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  Condition matters17-4PH in H1025 cuts differently from annealed stock.

Deep pockets and deep holes dominate cycle time. A pocket deeper than three times its cutter diameter forces a smaller tool, lower feed and more passes. In stainless steel that ratio hurts more than it does in aluminium because the small cutter rubs easily.

Thin walls are the second driver. Below about 1 mm on a 50 mm part, the wall deflects under cutting force and springs back, so you end up with a taper. We often leave stock, stress relieve and take a light finishing pass, which is real time on the quote.

Tolerances below ±0.05 mm come with inspection time, not just machining time. Our floor holds ±0.005 mm on the right features, but a drawing covered in tight tolerances on non-functional faces pays for metrology that the part does not need.

Threads, cross-holes and tight corner radii matter too. A 0.5 mm internal corner radius dictates the whole tool sequence for that pocket. Open it to 2 mm and the quote often drops by double digits.

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  Depth-to-diameterAbove 3:1 the cutter gets small, slow and fragile.
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  Wall thicknessUnder 1 mm, plan on extra passes and stress relief.
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  Tolerance densityTight callouts on non-functional faces add CMM time.
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  Corner radiusA bigger internal radius can remove a whole tool change.

Setup is charged once. A single prototype carries the full setup, programming, first-article inspection and fixture cost on one part. Ten identical parts spread that same cost across ten, so the unit price falls sharply even though the cycle time per part barely changes.

Fixtures are the quiet line item. A simple vise job needs almost nothing. A thin-walled or complex part may need a soft jaw set or a custom fixture, and that cost only pays back at a certain quantity. Ask where the break-even sits before you commit to a run size.

Bar stock and plate come in standard sizes. A part that fits a standard bar diameter avoids a special mill order and the extra material you pay for and then turn into chips. Sometimes a 2 mm design change saves more than a quantity increase.

There is no minimum order quantity here. One prototype or a 10,000-part run both go through the same quoting process, and production can start within 24 hours once the drawing and grade are confirmed.

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  Setup is one-timePrototypes look expensive because nothing is amortised.
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  Fixture paybackCustom workholding only makes sense above a certain run size.
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  Standard stockDesigning to standard bar sizes cuts material waste.
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  No MOQFrom one prototype to 10,000+ parts on the same process.

A 3D CAD file plus a 2D drawing is the fastest combination. STEP is our preferred neutral format, and IGES works when that is what you have. The 3D model defines the shape, and the 2D drawing carries tolerances, datums and notes that a model cannot express.

State the grade and the condition. "Stainless steel" is not enough. 303, 304, 316L, 420, 17-4PH and the rest behave differently enough that the grade alone can move a quote by a wide margin.

List the critical tolerances rather than tolerancing everything. Mark the faces that matter, the fits that must work, and leave the rest at a general block tolerance. That single habit removes unnecessary inspection cost and speeds up the DFM review.

Say what happens after machining. Passivation, bead blasting, polishing, laser marking and heat treatment all sit on the quote as separate operations. Tell us the finish and the quantity, and the number you get back matches the part you actually need.

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  STEP + drawingModel for geometry, drawing for tolerances and datums.
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  Exact gradeName the grade and the heat-treat condition.
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  Critical fewTolerance only the faces that function.
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  Post-processingPassivation, blasting and marking are separate operations.

On a 3-axis machine, a part with features on five faces needs multiple setups. Each setup adds fixture time, re-indicating and the risk of stack-up error. That is where the hours go, not into the cutting itself.

A simultaneous 5-axis center reaches those faces in one setup with a Ø400 mm rotary table. Setup count drops, and so does the fixture cost. For complex stainless parts this usually offsets the higher hourly rate of the machine.

Tool life improves as well. A short, rigid tool path with the tool kept normal to the surface cuts stainless steel more kindly than a long reach from a fixed spindle. Fewer regrinds, fewer offsets, better surface finish.

The trade-off is real. Simple prismatic parts with two or three setups are cheaper on a 3-axis machine. We quote on whichever route costs less, and 16 simultaneous 5-axis centers plus 27 three-axis machines means the choice is genuine.

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  Setup countFive-face features mean multiple setups on 3-axis.
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  RigidityShort normal-to-surface tools last longer in stainless.
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  Stack-up errorFewer setups means fewer accumulated tolerances.
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  Not always 5-axisSimple prismatic parts stay cheaper on 3-axis.