18-8 vs A2-70 vs 304 (short answer)
They describe different layers of the same stainless family — not three competing alloys.
| Name you see | What it actually is | Safe buying translation |
|---|---|---|
| 18-8 | US commercial nickname (~18% chromium, ~8% nickel) | Usually the 304 / A2 chemistry family — not a strength class |
| 304 (SUS304 / 1.4301) | Alloy / chemistry grade | The steel. Does not by itself prove fastener tensile class |
| A2-70 | ISO 3506-1 property class | A2 (304-family) stainless fastener with 700 MPa min tensile |
For a metric RFQ: write 304 / A2-70, plus the DIN/ISO head standard. “18-8” alone is too loose for OEM/MRO purchasing.
Pisenfasten’s published catalog is metric 304 / A2-70. Shop socket head cap screws or hex head screws. Need 316 / A4? See A2-70 vs A4-80 and contact sales.
What each name means
18-8 — US hardware language
18-8 is how many US catalogs, hardware stores, and older prints label austenitic stainless with roughly 18% Cr and 8% Ni. That chemistry window covers 304 and close cousins (sometimes 302). It does not tell you:
- Tensile / yield class of the finished screw
- Whether the lot is certified to ISO 3506-1
- Whether you received annealed “soft” stock or cold-worked fastener wire
Hardware-store 18-8 screws can be perfectly useful for light DIY. They are not automatically equivalent to a mill-certified A2-70 SHCS.
304 — the alloy
304 / SUS304 / EN 1.4301 is the chemistry grade. Typical uses: indoor equipment, frames, fixtures, electronics housings, general industrial joints that need stainless without 316 cost.
304 answers “what steel?”
A2-70 answers “how strong is this fastener?”
A2-70 — the fastener class
Under ISO 3506-1:
- A2 = austenitic stainless steel type (commercially the 304 family)
- -70 = property class → about 700 MPa minimum tensile for bolts/screws/studs (typically cold-worked)
Related A2 classes you may see:
| Class | Typical meaning |
|---|---|
| A2-50 | Softer / often annealed bar stock (~500 MPa min tensile) |
| A2-70 | Standard industrial fastener class (Pisenfasten catalog) |
| A2-80 | Higher A2 class (~800 MPa min). Less common in general catalogs |
More spec notes: A2-70 / 304 stainless fastener specs.
18-8 vs 304 vs A2-70 at a glance
| Question | 18-8 | 304 | A2-70 |
|---|---|---|---|
| Chemistry? | Nickname for ~18/8 Cr-Ni | Yes — alloy grade | A2 ≈ 304 family |
| Strength class? | No | No | Yes (ISO 3506-1) |
| Same as 316 / A4? | No | No | No |
| OK on a US hardware PO? | Informal | Better | Best for metric industrial RFQs |
| On Pisenfasten stock? | Don’t order by this name | Yes (as 304) | Yes — this is the catalog class |
Rule: 18-8 ≈ 304 chemically in commercial talk. A2-70 is 304-family plus a required fastener strength. Do not treat unmarked 18-8 as A2-70 without an MTC.
A2-70 vs A2-80 (not the same as A4-80)
GSC and buyer emails mix these up:
- A2-70 vs A2-80 — same A2 / 304 family, different strength. A2-80 is a real ISO class, not a typo. Do not assume a 304 A2-70 screw meets an A2-80 callout.
- A2-80 vs A4-80 — the -80 is the class; A2 vs A4 is the alloy. A4 ≈ 316 (molybdenum, better chlorides/marine). Buyers who type “A2-80” often meant A4-80. Confirm the print.
Chlorides, washdown, or “316 / A4” on the drawing → A2-70 vs A4-80. Do not substitute 304 / A2-70 without engineering approval.
When to put 304 / A2-70 on the PO
Use 304 / A2-70 when the print is metric and the environment is general industrial / indoor / mild outdoor:
- Machinery, fixtures, OEM frames
- Instrument and electronics housings
- MRO replacements that call 304, A2, 18-8, or “stainless” without 316
Still specify head standard + size:
- Socket head: DIN 912 vs ISO 4762
- Full-thread hex: DIN 933 vs ISO 4017
- Pitch: What is coarse pitch?
Shop 304 / A2-70 or send an RFQ
| Need | Go here |
|---|---|
| Socket head (SHCS) | Socket head cap screws |
| Hex head (DIN 933 / ISO 4017 family) | Hex head screws |
| Nuts / washers | Hex nuts · Flat washers |
| 316 / A4 or unmarked 18-8 replacement | Contact with the drawing |
Browse the parametric catalog or email the line below.
RFQ line (copy/paste)
Metric · [Head] · [Thread] × [Length] · coarse (or fine + pitch) · 304 / A2-70 · [DIN/ISO] · qty · ship-to
Example:
Metric SHCS · M6 × 20 · coarse · 304 / A2-70 · DIN 912 / ISO 4762 · 500 pcs · USA
→ sales@pisenfasten.com or Contact
Related searches
- 18-8 vs 304 stainless screws
- 18-8 vs A2-70
- is 18-8 the same as 304
- A2-70 vs 304
- a2-70 vs a2-80
- 18-8 stainless socket cap screw
FAQ
Q: Is 18-8 the same as 304?
A: Commercially, yes for most fastener buys — 18-8 is the US nickname for the 304 chemistry family. Always confirm on the MTC if the joint is specified.
Q: Is 18-8 the same as A2-70?
A: Not automatically. 18-8 is chemistry slang; A2-70 is a property class (~700 MPa min tensile). Ask for ISO 3506-1 A2-70 (or equivalent) plus chemistry.
Q: Can I replace A2-70 with hardware-store 18-8?
A: Only for non-critical, non-specified joints. If the drawing calls A2-70, 304, or a DIN/ISO fastener standard, order certified catalog parts.
Q: What about A2-80?
A: A2-80 is a higher A2 class, not 316. If the print says A4-80 / 316, that is a different alloy — see A2-70 vs A4-80.
Q: Do you stock 304 / A2-70?
A: Yes. Start at socket head cap screws or hex head screws, filter thread × length, or send the RFQ line to sales@pisenfasten.com.