Steel CNC Machining
1018, 1045, 4140 and tool steels — shafts, fixtures, and structural parts, with heat treatment and grinding coordinated per drawing.
Strength, Stiffness, and Wear Resistance on the Machine
Steel CNC machining covers the jobs aluminum can't take: high loads, wear surfaces, weldments, and parts that must hold hardness after heat treatment. We machine carbon, alloy, and tool steels daily — fixtures, shafts, gears, and structural components — and coordinate heat treatment, grinding, plating, and coating in the same order so the part arrives finished, not half-done. One PO, one accountable shop, no chasing a heat-treater across time zones.
Steel Grades We Machine
- 1018 (mild steel) — low-carbon, weldable, economical. The default for fixtures, brackets, plates, and parts that will be welded after machining
- 1045 — medium-carbon, stronger than 1018, through-hardenable. Shafts, pins, and moderate-wear components
- 4140 / 42CrMo — the workhorse alloy steel, typically machined pre-hardened at 28–32 HRC. High-strength shafts, gears, structural parts, and tooling
- 12L14 — leaded free-machining steel; the fastest-cutting steel for high-volume turned parts where the spec allows. Note: the lead content makes it unsuitable for welding and restricted in some regulatory regimes
- A2, D2, O1 tool steels — machined soft (annealed), then heat-treated to working hardness for dies, punches, and wear components
- A36 plate — structural plate for bases and frames
Machining Steel: What Actually Matters
- Machining before hardening — tool steels and hardenable alloys are machined in the annealed or pre-hard state; machining hardened steel above ~40 HRC is grinding territory, and we plan the route accordingly
- Heat-treat distortion — parts that harden after machining get grind stock left on critical features; we machine, heat-treat, then finish-grind to final dimension
- Tougher tooling — 4140 pre-hard runs on wear-resistant carbide grades with moderate speeds (roughly 300–500 SFM / 90–150 m/min) and rigid setups; expect cycle times 2–3× aluminum
- Chip control — steels make long, hot, continuous chips; chipbreaker geometry and high-pressure coolant keep the cut safe and the surface clean
- Stress relief — heavily pocketed steel workpieces get a stress-relief cycle between roughing and finishing to prevent movement after unclamping
- Rust prevention — machined steel surfaces start oxidizing in hours; parts are oiled or coated immediately after inspection and packed with VCI protection for sea freight
Tolerances and Surface Finishes
General features hold ±0.005 in (±0.13 mm); precision bores, shafts, and mating features to ±0.001 in (±0.025 mm), with ground surfaces to tighter callouts where the drawing requires. As-machined finish Ra 3.2 µm (125 µin); ground finishes to Ra 0.4 µm (16 µin).
Steel takes the widest industrial coating range: black oxide, zinc and nickel plating, phosphate coating, powder coat, and painting. Unfinished steel parts ship oiled. Specify the finish on the drawing and it's quoted with the machining — details on surface finishes.
Typical Steel Parts
Machine fixtures and jigs, shafts and spindles, gears and sprockets, structural brackets for high-load applications, hydraulic components, die and mold components, and weld-prep parts. Fixture and tooling work is a large share of our steel volume — if you need a matched set of jaws, nests, or locating fixtures, we machine the whole set to the same datums. Turned steel shafts run on our live-tooling lathes with milled flats and cross-holes completed in one setup.
What to Specify on the Drawing
State the grade and the condition — “4140 pre-hard 28–32 HRC” is a complete instruction; “steel” is not. If the part is heat-treated after machining, put the final hardness and the standard on the print, and mark which dimensions must hold after treatment so we leave grind stock in the right places. Call out the finish and its spec (black oxide per MIL-DTL-13924, zinc per ASTM B633, and so on), and flag any weld preparation so edges arrive the way your welder expects.
Steel Machining — Capability Summary
| Capability | Specification |
|---|---|
| Grades machined | 1018, 1045, 4140/42CrMo, 12L14, A2/D2/O1 tool steel, A36 (others on request) |
| General tolerance | ±0.005 in (±0.13 mm); precision features to ±0.001 in (±0.025 mm); ground tighter |
| Heat treatment | Through-hardening, case hardening, and stress relief coordinated per drawing |
| As-machined finish | Ra 3.2 µm (125 µin); ground surfaces to Ra 0.4 µm (16 µin) |
| Finishes | Black oxide, zinc/nickel plating, phosphate, powder coat, paint, oiled |
| Batch range | 1 pc prototype to 10,000+ pcs production |
| Typical lead time | Prototypes from 5 days; production typically 2–3 weeks (add time for heat treat) |
Quote Your Steel Parts
Upload STEP files and drawings — include hardness and finish callouts, and we'll quote machining, heat treatment, and coating together within 1–2 business days. Other materials on the materials page.
Quote Your Steel Parts
Upload STEP files and drawings — include hardness and finish callouts, and we'll quote machining, heat treatment, and coating together within 1–2 business days.
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