Hardened steel parts, by application

Die plates, die buttons, strippers and inserts that cut or form sheet metal. They fail by edge wear and chipping, so grade choice is a trade between carbide volume and toughness.

Typical route: Rough and drill soft, stress relieve, harden and double temper, then wire EDM the openings and grind the faces. Precision hole patterns are jig ground.

Die components: punches, buttons, strippers

Typical grades

• D2 (SKD11, 1.2379)
• A2 (SKD12, 1.2363)
• PM high-vanadium grades

Put on the drawing

• Cutting clearance per side, typically a percentage of sheet thickness set by the material being cut.
• Temper D2 at the high range (about 500-540 °C) when large openings are wire cut, to lower the risk of cracking.
• Flatness and parallelism of the die plate, so it seats in the die set.

Round and shaped punches that pierce or form. The tip sees impact and abrasion at once, so edge condition after grinding decides tool life.

Typical route: Turn or mill soft, harden, then cylindrical or profile grind. Shaped punches are wire cut and ground on the land.

Typical grades

• M2 (SKH51, 1.3343)
• D2
• A2

Put on the drawing

• Point size and head size with their own tolerances, and concentricity between them.
• Grinding direction on the land, lengthwise for clean stripping.
• Surface treatment (PVD or nitriding) applied after final grinding, never before.

Cavities and cores that shape plastic. Volume, abrasive fillers and the polish grade decide the steel.

Typical route: Pre-hardened P20 is cut to size with no furnace step. Through-hardened inserts are roughed soft, hardened, then hard milled. Sharp ribs and deep slots are sinker EDM. Polishing comes last.

Hardened mould inserts, cores and cavities

Typical grades

• P20 (1.2311), pre-hardened
• H13 (SKD61, 1.2344)
• 420 ESR (SUS420J2, 1.2083)

Put on the drawing

• Polish grade by face, using the SPI finish scale. Mirror grades need an ESR steel.
• Shut-off and parting line faces with their own tolerance.
• Cooling line positions, which are drilled before hardening.

Liners, guides, wear strips, cutting edges and bushings in conveyors, crushers and packaging lines. They are replaced by schedule, so repeatability between batches matters as much as hardness.

Typical route: Wear plate is bought hardened and cut by waterjet or wire, then drilled with carbide or EDM. Tool steel wear strips follow the rough, harden, grind route.

Wear plates and liners at 400-500 HB

Typical grades

• D2
• A2
• Abrasion-resistant plate, 400-500 HB
• 52100 for bushings

Put on the drawing

• Which face wears, and how much wear is allowed before replacement.
• Bolt hole pattern to the mating frame, often looser than it is drawn.
• Hardness as a range (for example 58-60 HRC or 400-450 HB), with the test location.

Plug and ring gauges, snap gauges, setting masters and fixture locators. They must keep their size for years, so stability counts more than toughness.

Typical route: Harden, sub-zero treat to reduce retained austenite, temper more than once, then grind and lap to size. Some routes add a stabilising temper between grinding and lapping.

Hardened gauges and fixtures: stability

Typical grades

• 52100 (SUJ2, 1.3505)
• O1 (SKS3, 1.2510)
• A2
• D2

Put on the drawing

• Gauge tolerance class, for example to ISO 1938-1 or the US gauge maker classes.
• Measuring temperature, 20 °C under ISO 1.
• Sub-zero treatment and the number of tempers, written on the drawing.

Spindles, drive shafts, guide pins and dowels. A tough core with a hard surface is the usual goal, which a through-hardened, case hardened or induction hardened route can each give.

Typical route: Turn soft between centres, heat treat, then hard turn or cylindrical grind the journals. Pre-hardened 4140 at 28-32 HRC is turned to size with carbide.

Hard turning vs cylindrical grinding

Typical grades

• 4140 (SCM440, 1.7225)
• 52100
• 8620 and 9310, case hardened

Put on the drawing

• Case depth and surface hardness for case or induction hardened parts.
• Which diameters are ground and which are left turned.
• Runout of journals to the centre axis, not to an outside diameter.