SS · stainless
Stainless Steel 416
The martensitic free-machining grade - the best-machining stainless on this list and the one that hardens after machining, unlike the austenitics.
Quoting this material
- Typical lead time
- 7–12 working days
- Condition
- Annealed; hardenable by heat treatment to 26–40 HRC
- Achievable finish
- Ra 1.6 µm typical · Ra 0.4 µm best
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
The martensitic free-machining grade - the best-machining stainless on this list and the one that hardens after machining, unlike the austenitics.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 585 | MPa |
| Yield strength (0.2%) | 480 | MPa |
| Elongation | 20 | % |
| Hardness (annealed) | 262 | HB |
| Thermal conductivity | 24.9 | W/m·K |
| Modulus of elasticity | 200 | GPa |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
Annealed; hardenable by heat treatment to 26–40 HRC
Heat treatment
Martensitic: harden by austenitising and quenching, then temper to the required strength and toughness. That combination is the reason to specify 416 rather than a 300-series grade - you cannot harden 304 at all.
Achievable surface finish
Ra 1.6 µm
Ra 0.4 µm
Machines to a good finish and takes a black oxide or passivated finish; corrosion resistance is below 304.
Tooling and cutting parameters
Cutting speed
- 150–250 m/min (carbide)
Feed
- 0.10–0.30 mm/rev turning · 0.08–0.15 mm/tooth milling
Tooling
- Coated carbide; uncoated is also fine at the lower end of the range
Coolant
- Flood
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Shafts, spindles and stems
- Valve and pump parts
- Screws and fasteners for wet service
- Bushings and wear sleeves
- Cutlery and instrument hardware
DFM notes for this grade
- Corrosion resistance is a step below 304 and the machinability advantage is a step above - the trade has to be deliberate
- It is magnetic and hardenable, which is often why it was specified; check which of those two properties the design actually needs
- Welding is not advisable in high-strength sections; design for mechanical assembly
Questions buyers ask
- Why choose 416 rather than 303 if both are free-machining?
- Because 416 can be hardened. A shaft that runs in a bearing, a stem that wears against a seat, or anything that needs 40 HRC cannot be made from 303 at all - austenitic stainless is not hardenable. You trade some corrosion resistance for that capability.
- Does 416 rust?
- Yes, more readily than 304. It is a martensitic grade with less chromium in solution after hardening, and it pits in chlorides. In a damp industrial environment, black oxide plus oil or a light passivation is normal.