Notes on machining hardened and tool steel: hard milling, grade selection, and writing a quotable RFQ.https://hardsteelcnc.com/en-ushttps://hardsteelcnc.com/blog/jig-grinding-hardened-die-plates/https://hardsteelcnc.com/blog/jig-grinding-hardened-die-plates/Jig grinding finishes holes in hardened steel to a few microns of position. When the tolerance justifies it, when wire EDM or hard milling will do, and what to specify.Sun, 18 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/hardness-testing-tool-steel-parts/https://hardsteelcnc.com/blog/hardness-testing-tool-steel-parts/Rockwell C, Vickers and portable testers read tool steel differently. How to pick the method, where to put the indent and what to write on the drawing.Sat, 17 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/hardened-injection-mold-inserts-cores-cavities/https://hardsteelcnc.com/blog/hardened-injection-mold-inserts-cores-cavities/How hardened mold inserts, cores, cavities and slides are made and specified: steel and hardness by function, fits, vents and the details that prevent flash.Fri, 16 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/hardened-gauges-fixtures-stability-stress-relief/https://hardsteelcnc.com/blog/hardened-gauges-fixtures-stability-stress-relief/Hardened gauges and fixtures must hold size for years. How steel choice, stress relief, ageing and grinding sequence decide stability, and what to specify.Thu, 15 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/h11-vs-h13-hot-work-tool-steel/https://hardsteelcnc.com/blog/h11-vs-h13-hot-work-tool-steel/H11 and H13 differ mainly in vanadium. How they compare for die casting and forging dies in toughness, wear, heat treat and machinability, and when each is better.Wed, 14 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/forming-rolls-roll-forming-lines-grade-hardness/https://hardsteelcnc.com/blog/forming-rolls-roll-forming-lines-grade-hardness/Roll forming tooling decides profile accuracy and tool life. Which tool steel and hardness suit the strip, how profiles are finished and what the drawing needs.Tue, 13 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/cryogenic-treatment-d2-m2-tool-steel/https://hardsteelcnc.com/blog/cryogenic-treatment-d2-m2-tool-steel/Cryogenic treatment of D2 and M2 converts retained austenite and may extend tool life, but results vary. What it does, where it fits in the cycle and how to specify it.Mon, 12 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/case-hardening-vs-through-hardening-8620-9310-4140/https://hardsteelcnc.com/blog/case-hardening-vs-through-hardening-8620-9310-4140/Case hardened 8620 or 9310 gives a hard shell on a tough core. Through hardened 4140 is hard throughout. Distortion, grinding stock, cost and failure compared.Sun, 11 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/52100-bearing-steel-hard-turning/https://hardsteelcnc.com/blog/52100-bearing-steel-hard-turning/52100 bearing steel at 58 to 64 HRC can be hard turned with CBN instead of ground. What tolerance and finish hard turning holds and where grinding still wins.Sat, 10 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/420-stainless-mold-steel-polishing-hardness/https://hardsteelcnc.com/blog/420-stainless-mold-steel-polishing-hardness/420 stainless mold steel suits clear plastic and corrosive resin molds. Its hardness range, polish quality, corrosion limits and the heat treat steps that decide them.Mon, 05 Oct 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/rfq-checklist-hard-steel-parts/https://hardsteelcnc.com/blog/rfq-checklist-hard-steel-parts/Why hardened steel quotes come back wildly different, and the seven pieces of information that make shops price the same job. A checklist to run before you send the drawing.Mon, 21 Sep 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/tooling-work-moving-to-vietnam/https://hardsteelcnc.com/blog/tooling-work-moving-to-vietnam/Vietnam has a real tool and die base built by mould and electronics manufacturing. An honest look at where it is competitive on hardened steel and where it is not.Thu, 17 Sep 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/tool-steel-grade-equivalents-aisi-jis-din/https://hardsteelcnc.com/blog/tool-steel-grade-equivalents-aisi-jis-din/D2, SKD11 and 1.2379 are the same steel under three standards. A cross-reference table for tool steel grades, and why naming the equivalent shortens your lead time.Mon, 14 Sep 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/vetting-a-hard-steel-machine-shop/https://hardsteelcnc.com/blog/vetting-a-hard-steel-machine-shop/Every shop shows the same photos of the same machines. Eight questions that separate shops which actually machine at 60 HRC from shops that own capable equipment.Thu, 10 Sep 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/4140-p20-pre-hardened-steel-machining/https://hardsteelcnc.com/blog/4140-p20-pre-hardened-steel-machining/Most hardened steel parts are not 60 HRC exotics. They are 30-35 HRC 4140 and P20. What those grades hold, how they machine, and where they stop being enough.Mon, 07 Sep 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/inspecting-hardened-parts-cmm-hardness-testing/https://hardsteelcnc.com/blog/inspecting-hardened-parts-cmm-hardness-testing/CMM reports, hardness tests and finish traces each prove something different, and a standard proof package misses the failures that matter most on hardened steel.Thu, 03 Sep 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/d2-vs-h13-tool-steel-machinability/https://hardsteelcnc.com/blog/d2-vs-h13-tool-steel-machinability/D2 and H13 sit at similar hardness but behave differently on the machine. A practical comparison of carbide content, abrasion, thermal behaviour and what each does to lead time.Wed, 02 Sep 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/o1-vs-a2-oil-vs-air-hardening/https://hardsteelcnc.com/blog/o1-vs-a2-oil-vs-air-hardening/O1 is cheaper and machines easier. A2 moves less in heat treatment. A look at what that difference is worth once you price the finishing operation it forces.Mon, 31 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/heat-treat-distortion-stress-relief-allowance/https://hardsteelcnc.com/blog/heat-treat-distortion-stress-relief-allowance/Parts move in the furnace. How much, why, and the three drawing decisions — allowance, stress relief and datums — that decide whether you can machine it back.Thu, 27 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/machining-hardened-steel-after-heat-treatment/https://hardsteelcnc.com/blog/machining-hardened-steel-after-heat-treatment/Hard milling at 55-62 HRC is not soft machining with a slower feed. What changes in tooling, fixturing, stock allowance and quoting when the part is cut after heat treat.Wed, 26 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/s7-tool-steel-machining/https://hardsteelcnc.com/blog/s7-tool-steel-machining/S7 trades wear resistance for toughness that no cold work grade can match. Where it belongs, how it machines, and the heat treat detail that ruins parts when missed.Mon, 24 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/white-layer-surface-integrity-hardened-steel/https://hardsteelcnc.com/blog/white-layer-surface-integrity-hardened-steel/A dimensionally perfect hardened part can carry a re-hardened surface layer with tensile stress underneath. What causes it, why CMMs miss it, and how to specify against it.Thu, 20 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/a2-vs-d2-tool-steel/https://hardsteelcnc.com/blog/a2-vs-d2-tool-steel/A2 and D2 are both air-hardening cold work steels, but they fail differently and machine differently. Which to specify for punches, dies and forming tools.Mon, 17 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/hard-milling-troubleshooting-chatter-chipping-drift/https://hardsteelcnc.com/blog/hard-milling-troubleshooting-chatter-chipping-drift/Three failure modes cover most hard milling problems. How to tell them apart from the part and the tool, and the fix order that solves each without guessing.Thu, 13 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/hybrid-routing-hard-mill-grind-ctq-faces/https://hardsteelcnc.com/blog/hybrid-routing-hard-mill-grind-ctq-faces/The cheapest way to finish a hardened part is rarely one process. How to split a drawing between milling and grinding, and how to mark it so shops quote the same plan.Mon, 10 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/rigidity-runout-stickout-workholding-hard-milling/https://hardsteelcnc.com/blog/rigidity-runout-stickout-workholding-hard-milling/Hard milling fails on vibration, not on power. The four rigidity variables that decide whether a 60 HRC surface comes out at Ra 0.4 or covered in chatter marks.Thu, 06 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/pre-hardened-vs-through-hardened-tool-steel/https://hardsteelcnc.com/blog/pre-hardened-vs-through-hardened-tool-steel/Buying steel already at 30-40 HRC skips heat treatment entirely. When that is the right call for a die or mould, and when it costs you the wear life you needed.Mon, 03 Aug 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/trochoidal-dynamic-toolpaths-hardened-steel/https://hardsteelcnc.com/blog/trochoidal-dynamic-toolpaths-hardened-steel/Hard milling fails at the corners, where engagement spikes. How trochoidal and dynamic toolpaths keep the load constant, and the parameters that actually matter.Thu, 30 Jul 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/wire-edm-sharp-internal-corners-hardened-dies/https://hardsteelcnc.com/blog/wire-edm-sharp-internal-corners-hardened-dies/No milling cutter produces a truly sharp internal corner. Where that forces wire EDM into a hardened die, what it costs in time, and how to design around it when you can.Mon, 27 Jul 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/dry-machining-air-blast-mql-hardened-steel/https://hardsteelcnc.com/blog/dry-machining-air-blast-mql-hardened-steel/Flood coolant on an interrupted hard milling cut destroys CBN edges. Why heat is a tool in hard machining rather than a problem, and when MQL earns its place.Thu, 23 Jul 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/hard-turning-vs-cylindrical-grinding/https://hardsteelcnc.com/blog/hard-turning-vs-cylindrical-grinding/Hard turning finishes hardened shafts and bores on a lathe instead of a grinder. What it holds, where it fails, and the four conditions that make it the cheaper route.Mon, 20 Jul 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/cbn-vs-carbide-vs-ceramic-hardened-steel/https://hardsteelcnc.com/blog/cbn-vs-carbide-vs-ceramic-hardened-steel/Three cutting materials cover hardened steel, and the crossover points between them are narrower than most shops assume. Where each one wins and where each one shatters.Thu, 16 Jul 2026 00:00:00 GMThttps://hardsteelcnc.com/blog/hard-milling-vs-grinding-vs-wire-edm/https://hardsteelcnc.com/blog/hard-milling-vs-grinding-vs-wire-edm/Three ways to finish a hardened steel part, and the geometry, tolerance and volume rules that decide which one belongs on your drawing. With a side-by-side comparison.Mon, 13 Jul 2026 00:00:00 GMT