Direct answer: Which grade, for which sensor, and why. Wall thickness, magnetism, temperature and media.
Why stainless is the default for sensor housings
- No plating tolerance. A 304 or 316L housing is corrosion resistant through its whole section, so the drawn wall thickness is the only thickness in play.
- Thin walls keep their strength. Stainless work hardens as it is drawn, so a 0.3-0.6 mm wall holds up where carbon steel would need more thickness or a coating.
- It survives the thermal cycle. Coolant, oil and pressure sensors run from -40 C cold soak to 150 C in service; exhaust-side sensors see 800-900 C.
- It is compatible with the media. Glycol coolant, ethanol and biodiesel blends, brake fluid and exhaust condensate attack plated carbon steel far faster than they attack 304 or 316L.
Source: balford.net/materials/stainless-steel/.
Which grade, for which sensor
| Sensor | Typical housing grade | Why that grade |
|---|---|---|
| Oxygen / lambda (upstream) | 304, 310S | 900 C exhaust gas and thermal shock on start-up |
| NOx | 304, 310S | High temperature plus acidic condensate |
| Exhaust gas temperature (EGT) | 304, 316L, 310S | Continuous high temperature and vibration |
| ABS / wheel speed | 304, 316L | Road salt, brake dust and stone impact; non-magnetic |
| Coolant / water temperature | Brass (C3604, C3771) or 304 / 316L | Brass conducts heat about 10x faster, so the thermo-well responds |
| Oil and fuel pressure | 304, 316L | Fuel, oil and additive compatibility |
| Position / speed (magnetic circuit) | 430 / 1.4016 | Ferritic grade provides the magnetic return path |
Material grade is confirmed against the application before tooling.
Magnetic or non-magnetic is a sensing decision
304 and 316L are effectively non-magnetic. 430 ferritic stainless is magnetic, and it provides the magnetic return path where the sensing principle needs one.
Which grade a housing needs is decided by the sensing principle, not by cost.
This is why "stainless steel housing" is an incomplete specification: two grades that look identical on paper can behave completely differently inside the sensor.
Ask the sensor designer which of the three matters most: corrosion duty, magnetic requirement, or service temperature.
What our catalogue actually uses
| Material | Configurations | Material | Configurations |
|---|---|---|---|
| 310 stainless | 127 | Copper | 3 |
| 316 stainless | 57 | 305 stainless | 2 |
| 304 stainless | 47 | 632 stainless | 2 |
| 430 stainless | 9 | 201 / 309 / 65Mn | 1 each |
| 301 stainless | 6 | Not stated in source | 142 |
From Balford's open dataset of 398 deep drawn sensor housing configurations across 10 series. The weight of 310 and 309 is consistent with exhaust-side service, where oxidation resistance at temperature does the work.
How stainless changes the drawing process
- Lower single-draw ratio: about 1.6-1.8 for 304/316, against 1.8-2.0 for low-carbon steel. Tall parts need more draws, and need them sooner.
- Die clearance per side about 1.2-1.4 x material thickness, against 1.1-1.3 x for steel.
- Work hardening: every draw hardens the material, so an intermediate anneal arrives earlier than it would with carbon steel.
- Tooling wear is higher and lubricant choice matters more, because friction at the die radius is where tearing starts.
A stainless part is not a carbon steel part in a different material. It is a different manufacturing route.
Tolerance and finish notes
- Diameters repeat well because they are set by tooling.
- Wall thickness is a gradient, not a constant, so the tolerance must be tied to a measurement position.
- Wall height is the least precise dimension because the top edge is trimmed.
- Inside finish can be excellent: it is formed against the punch rather than cut, which is why drawn bores suit armature guidance and sealing surfaces.
- Outside finish will carry draw marks unless a finishing operation is added.
- 0.001 mm applies only to selected critical machined features where process, geometry, material and inspection conditions allow. It is not a general tolerance for a drawn housing.
Standard capability on deep drawn features is about +/-0.05 to +/-0.25 mm; tighter features are evaluated from the drawing.
What is outsourced, and why we say so
- Passivation of stainless housings is performed by audited partner companies and is declared as such.
- Bulk heat treatment, plating, passivation, electropolishing, phosphating and powder coating are likewise partner operations.
- Machining pre-forms (hot forging, cold extrusion, cold heading, casting, powder metallurgy) are bought as near-net shapes and finished by machining in house. Stamped blanks are made on our own presses.
- Slow-wire EDM is the one tool room operation we subcontract.
- We are ISO 9001:2015 certified. Process controls are aligned with IATF 16949 requirements; we are not certified to IATF 16949 and do not hold ISO 14001.
We would rather state the boundary than have you discover it during an audit.
Frequently asked
| Question | Answer |
|---|---|
| Do you deep draw stainless steel? | Yes. Housings, sleeves and cups in 304 and 316-class grades are core work, with controlled wall thickness and surface finish. |
| Which grades do you regularly run? | We regularly process 304 and 316-class stainless. Other grades on request, confirmed against the application and drawing before quoting. |
| Is stainless more expensive than carbon steel? | Generally yes, on both material and tooling wear. Quoting is based on grade, thickness and complexity. |
| Can you supply material certificates? | Yes, on request. |
Low-carbon steel and pure iron remain the economical choices where corrosion and temperature are not the deciding factors.
Related pages
- All Balford engineering resources
- RFQ, IMDS and supplier audit checklists
- Deep drawing: the complete technical guide
- Send a drawing for a DFM review
Printable version
This document is also available as a PDF: Stainless Steel Grades for Deep Drawn Sensor Housings (PDF).