O1 Tool Steel CNC Machining
O1 Tool Steel CNC Machining for Tooling, Fixtures and Precision Tool Parts
O1 is one of the most common oil-hardening tool steels we see in tooling work, and it is also one of the easiest to machine badly. Machined in the wrong condition, or sequenced without regard to hardening, it can move enough to put a fixture pin or a punch out of tolerance before it reaches assembly.
We machine O1 parts with the heat treatment and finishing steps already planned, so the material and the drawing agree at every stage.
How We Approach O1 Material Condition
Most O1 bar and plate arrives annealed, which is the condition we prefer for roughing. In that state the steel is soft enough for efficient milling and turning, and stock removal is predictable. We ask for the material standard, heat lot or certificate, and the supplied hardness when it is available, because a bar that is not in the expected condition changes the machining plan.
We also check for surface conditions that will matter after hardening. Decarburized skin, scale, or uneven stock can cause size and hardness variation, so we account for it in the stock allowance rather than discovering it at the hardness tester. For parts supplied pre-hardened, we confirm the target range and adjust cutting parameters and tooling accordingly.
Heat Treatment Sequence and Dimensional Change
O1 hardens by oil quenching, and the process introduces distortion that is normal for this steel but must be managed. Thin sections, long slender pins, and parts with large variations in wall thickness are the cases where we most often recommend an intermediate stress relief or a rough-finish-harden-finish sequence.
Heat treatment is not an in-house process at YJCNC. Where hardening is required, we define the sequence in our process plan and coordinate with a heat treatment source that you approve or that is named in your specification.
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1
Rough Machine
Remove bulk stock in the annealed state, leaving a defined allowance on all hardened features.
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2
Stress Relieve
Applied where geometry warrants it, such as thin sections or long slender pins, before final hardening.
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3
Harden and Temper
Oil quench to the specified hardness range with the tempering requirement defined in advance.
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4
Finish to Size
Finish holes, bores and locating faces to final tolerance, with the tightest features machined last.
Size change after hardening is the reason we do not recommend finishing O1 features to final tolerance before heat treatment unless the drawing allows it. The allowance depends on part geometry, section size and the tolerance band, and we set it for each part rather than applying a generic figure. We need the target hardness range, the tempering requirement, and any distortion limits so hardening and finish machining are planned together.
Machining Capacity for O1 Parts
Our equipment base lets us machine O1 components across the full range of tooling geometries, from simple plates and blocks to turned punches and multi-sided fixture bodies. Select a machine group below for its typical use.
- 3-axis machining centers
- 25 units
- 4-axis and 5-axis machining
- 9 units
- CNC lathes and turn-mill
- 58 units
- Swiss-type lathes
- 10 units
Where hardened parts need finish operations, we plan toolpaths, fixturing and the order of finishing passes around the expected distortion, so the features that carry the tightest tolerances are finished last.
Inspection and Acceptance Records
Verification for O1 parts follows the drawing and the material requirements. We use our coordinate measuring machine for three-dimensional and geometric checks, optical measuring systems for profiles and hole positions, and a surface roughness tester for finish requirements.
Hardness is checked on a Rockwell hardness tester against the specified scale and range, and we can provide the results with the shipment documentation. Our quality systems are certified to ISO 9001, ISO 13485, AS9100D, ISO 14001, and IATF 16949; aerospace work is supported under AS9100D; any inspection or traceability record we issue reflects the drawing and the quality requirements you specify.
Dimensional and Hardness Tools
- Coordinate measuring machine, optical measuring systems and surface roughness tester
- Rockwell hardness tester for hardness verification against the specified scale
- Calibrated micrometers, height gauges, gauge blocks and pin gauges
- Thread gauges in the M1.0 to M16 range
Part Types We Typically Machine in O1
Parts with long, slender geometry or fine features need more planning than solid blocks, and we will say so in the quote rather than promise the same result on every shape.
- Locating pins and bushings
- Punches and dies
- Gauge and inspection fixture bodies
- Wear plates and shims
- Custom tool components that need hardness combined with stable dimensions
Is O1 the Right Material for Your Part?
O1 suits parts that need good hardness after oil quenching, reasonable wear resistance, and machinability in the annealed state. It is often the right choice for general tooling and fixture components with moderate production volumes.
Where a part sees very high wear, very high temperature, or needs the best possible dimensional stability after hardening, a different tool steel or a stainless grade may fit better. If you are unsure, send us the operating conditions along with the drawing, and we will review whether O1 fits the application before you commit to a material.
Send Us Your O1 Requirements for a Quote
To give you an accurate quotation and process plan, please include the following with your request:
- Drawing or 3D model with tolerances, surface finish, and hardened or unhardened feature callouts
- Material standard and condition (annealed, pre-hardened, or as-received), with certificate or heat lot if available
- Target hardness range, tempering requirement, and hardness locations on the part
- Distortion limits or features that must be finished after heat treatment
- Quantity, delivery expectations, and required inspection or documentation
Email: info@yjcncmachining.com
Phone:
WhatsApp:
Address: Yabian Community, Shajing Street, Baoan District, Shenzhen, China
Our engineering team will review the part and reply with a machining sequence, stock allowance recommendations and a quotation. YJCNC will confirm the material condition, heat treatment approach and inspection scope before production starts.