Chemical Etching Formula
SK5 Tool Steel
with FeCl₃+HCl
Formula Summary
The table below summarizes every parameter that defines this etching formula. Values listed as ranges scale with sheet thickness across the supported band.
Why FeCl₃+HCl for SK5 Tool Steel?
Ferric-chloride-based formulas are the industrial workhorse for ferrous, nickel, and copper-bearing alloys like SK5 Tool Steel. The Fe³⁺ ion oxidizes the metal surface; where HCl is present it regenerates dissolved species and stabilizes chloride concentration. The result on SK5 Tool Steel is anisotropic etching with predictable undercut and an easily regenerated spent bath.
Process Window & Bath Control
The process window for this FeCl₃+HCl formula centres on 50°C and 44 °Bé. Conveyor speed spans 0.19-1 m/min over the 0.1-0.3 mm thickness band; the typical operating point is 0.35 m/min. Every 5°C drop in bath temperature requires roughly a 30% reduction in conveyor speed to hold the same etch depth, so temperature stability is the single biggest lever on consistency.
Design Rules & Tolerances
When laying out artwork for SK5 Tool Steel at through etch (double-sided), plan for a minimum hole diameter in the 120-360 μm range and a minimum line width in the 100-300 μm range, depending on the chosen sheet thickness within 0.1-0.3 mm. The etch factor of ~2.70 and undercut range of 19-56 μm determine how much the mask must be biased to land the finished dimension on target.
• Minimum hole diameter range: 120-360 μm
• Minimum line width range: 100-300 μm
• Single-side undercut range: 19-56 μm
• Typical etch factor (EF): 2.70
Yield & Production Economics
Expect a yield in the 96-96.5% range for SK5 Tool Steel with FeCl₃+HCl, with 96.3% typical on a well-controlled line. Most rejects trace back to upstream coating and exposure rather than to the etch bath itself, so tightening photolithography control is usually the fastest path to a higher number.
Typical Applications
Typical applications for SK5 Tool Steel processed with FeCl₃+HCl include spring elements, blades, shim stock, and stamped-replacement flat parts. The formula's tolerance band and yield make it well suited to medium-to-high-volume precision flat parts.
Process Equipment & Material Reference
On the shop floor, this SK5 Tool Steel + FeCl₃+HCl recipe is implemented on a wet chemical etching machine. The 50°C bath setpoint and 0.19-1 m/min conveyor range correspond to verified production envelopes on that equipment for through etch (double-sided).
If you need a wider view of steel beyond this single recipe, our Steel chemical etching guide covers grade selection, photoresist compatibility, and typical industries that consume this metal in etched form.
Production Use Cases for This Formula
Typical end-uses for SK5 Tool Steel run on this formula include soy-milk-maker filtration mesh, stainless steel metal filter mesh, and stainless steel shower-head filter mesh. The 50°C bath and 0.1-0.3 mm supported thickness range cover most of the production work in these segments without re-tuning chemistry.
Adjacent applications usually transfer onto this same formula with no chemistry change, sometimes only a conveyor speed tweak. Drop a drawing and a target volume and we will return a process card built off the parameters on this page.
More Carbon & Tool Steel Formulas
Other formulas in the same material family.
Frequently Asked Questions
Sources & References
- ASTM E407: Standard Practice for Microetching Metals and Alloys
- ASTM B912: Standard Specification for Passivation of Stainless Steels
- Photo Chemical Machining Institute — process capability guidelines
- NIST Engineering Statistics Handbook — process tolerance and capability
Standards are referenced for context. Always confirm parameters against the current published edition and your own process validation.
Need a Quote for This Process?
WET Etched runs production wet chemical etching lines using the FeCl₃+HCl chemistry. Send us your part drawing and quantity for a full process quote.