Part types compared
A bolt, a nut and a washer are three different processing problems. This table is the short version; each page carries the numbers.
Which finish a part needs is decided by its thread allowance, its property class and how it behaves in a barrel — not by the material alone. This index covers the 8 part types V.S. Heat Treatment processes in bulk: bolts, nuts, screws, washers, pins, springs, anchor bolts and fasteners in general. Each page gives the hardness band, the coating thickness the thread can absorb, the standards that apply and the defects to watch for. All are small parts run at volume in Samut Sakhon under ISO 9001:2015.
The row that changes most between part types is not the material — it is the fit. An external thread at 6g has a finite allowance for coating, an internal thread at 6H has none, a dowel pin has an eight-micron diameter band, and a washer has nothing to gauge at all. That one difference decides the coating thickness, the handling route and often whether electroplating is the right process at all.
Thread class, size band, strength standard and relief bake, by part type
| Part type | Thread / fit | Size band | Strength spec | Coating | Relief bake |
|---|---|---|---|---|---|
| BoltsBarrel or rack | ISO 965-1 · 6g | M5 – M36 | ISO 898-1 · 8.8 – 12.9 | SC 2 · Fe/Zn 8 | Triggered by class — 10.9 and above |
| NutsBarrel | ISO 965-3 · 6H | M3 – M30 | ISO 898-2 · proof load, class 4 – 12 | SC 1 – SC 2 · Fe/Zn 5–8 | Rarely triggered |
| ScrewsBarrel | ISO 965-1 · 6g · ISO 1478 ST | M1.6 – M8 | ISO 898-1 4.8 – 12.9 · ISO 2702 for ST | SC 1 · Fe/Zn 5 | Triggered by class — 10.9 and above |
| WashersBarrel | ISO 7089 / DIN 6796 · no thread | ø3 – ø24 mm | no property class — 100/200/300 HV classes | SC 2 – SC 4 · Fe/Zn 8–25 | Depends on the hardness class |
| PinsBarrel | ISO 8734 · m6 diameter fit | ø1.5 – ø20 mm | no property class — double shear + m6 | SC 1 or phosphate + oil | Usually required if electroplated |
| SpringsBasket / spaced | EN 10270 / JIS G 3522 · no thread | wire ø0.5 – ø6 mm | no property class — wire grade + load at test length | SC 1 · Fe/Zn 5, or non-electrolytic | High risk — consider a non-electrolytic coating |
| Anchor BoltsRack | ISO 965-1 · 6g · ASTM F1554 | M12 – M36, 200 – 1 000 mm | ISO 898-1 4.6 – 8.8 · ASTM F1554 Gr 36/55/105 | SC 3 – SC 4 · Fe/Zn 13–25 | Triggered by class — 10.9 and above |
| FastenersBarrel or rack | ISO 965 · 6g / 6H | M1.6 – M36 | different standard per family — see each page | SC 1 – SC 4 · bounded by the fit | Triggered by class — 10.9 and above |
Values are typical ranges that depend on the part and the governing specification. Follow a row through to its page for the arithmetic behind it.
Four questions decide the route
- 1What is the tightest fit on the part?External thread, internal thread, ground diameter or nothing at all. Electroplating grows an external pitch diameter by about four times the coating thickness, grows a pin diameter by twice, and eats the whole of a 6H internal thread. The fit sets the coating ceiling before corrosion is even discussed.
- 2Which strength standard governs it?ISO 898-1 property classes for bolts, screws and studs. ISO 898-2 proof load for nuts. ISO 2702 surface and core hardness for tapping screws. A wire grade and a load at test length for springs. Nothing at all for plain washers and pins.
- 3Can this part run in a barrel, or does it need racking?Hex nuts and short bolts tumble cleanly and run barrel. Flat washers stack and shadow. Coil springs tangle and nick. Anything past roughly 150 mm will not fit the process at all. Handling changes the price model from per-kilogram to per-piece.
- 4Does this part need hydrogen de-embrittlement baking?ISO 4042 puts it at property class 10.9, or about 390 HV. Above that line an electroplated part needs de-embrittlement relief started as soon as possible and normally within 4 hours. Hardened pins, springs and conical washers are over the line even though they have no property class.
Guidance based on published standards and general fastener metallurgy. Every figure is a typical range that depends on the part, the material and the governing specification — the customer drawing and the applicable standard always prevail. Coating designations describe what a drawing can call for, not a result guaranteed on your parts without testing.