Process & Material
Invar 36 Small Hole EDM Drilling Feasibility Review
Invar 36 can be machined with Small Hole EDM when the geometry matches small through holes, deep holes, angled holes, cooling holes, vent holes, and start holes in hard or heat-resistant alloys. Invar 36 is a low-expansion iron-nickel alloy selected for dimensional stability across temperature changes; the supplied condition affects support, discharge energy, finishing, and inspection.
Quick Answer
Small Hole EDM is suitable for Invar 36 when the feature is a small, deep, angled, cooling, vent, or start hole in conductive material. The supplied condition must be stated before tolerance and surface requirements are confirmed.
Key Material Decisions
How This Material Behaves
A low-expansion iron-nickel alloy selected for dimensional stability across temperature changes. In Small Hole EDM, the supplied condition changes bore stability, breakthrough quality, wall finish, and the inspection plan for straightness and position.
Choosing the Right Condition
Choose Small Hole EDM for small through holes, deep holes, angled holes, cooling holes, vent holes, and start holes in hard or heat-resistant alloys. State the exact Invar 36 condition, then set tolerance, finish, support, and inspection from the controlled feature rather than the whole part.
Risks to Manage
For Small Hole EDM, residual stress and asymmetric stock removal can undermine the low-expansion design intent. The far end of the hole can drift even when the entry diameter and start position remain stable during the final portion of a high-aspect-ratio hole; acceptance must focus on temperature-sensitive datums and low-expansion geometry. On Invar 36, the resulting defect can be position or taper error that is masked until the part and inspection system stabilize thermally. For Invar 36, stabilize workpiece and inspection temperature, finish from controlled datums, and measure only after the part has thermally settled. Inspect entry, exit, taper, position and wall condition independently; document stabilized geometry, datum relationship and inspection temperature for Invar 36.
How Small Hole EDM Works on Invar 36
Small Hole EDM advances a rotating tubular electrode through Invar 36 while dielectric exits at the cutting tip. Electrode wear, runout, internal flushing, true hole depth and breakthrough support control entry-to-exit diameter, taper, straightness and wall condition. Hole diameter, depth and depth-to-diameter ratio—not stock thickness alone—define the process limit.
Small Hole EDM Capability Reference
| What you're asking | What you can expect |
|---|---|
| Feature types | small through holes, deep holes, angled holes, cooling holes, vent holes, and start holes in hard or heat-resistant alloys |
| Tolerance | ±0.010–0.050 mm |
| Surface finish | Hole-wall finish is feature-dependent |
| Typical diameter | About 0.3–3.0 mm for ordinary planning |
| Depth driver | Depth-to-diameter ratio, straightness, and breakthrough |
| Main limitation | Very small diameter combined with extreme depth may require specialized equipment, staged electrodes, and dedicated metrology. |
Material Condition Reference
| Condition | What to expect | Watch out for | Surface notes |
|---|---|---|---|
| solution annealed | Use stable support and conservative energy. | High-temperature alloys can retain a hard recast layer. | Identify fatigue and hot-section faces before finishing. |
| cold-worked or stabilized | Account for cold-work and service stress. | Thin features can move and electrode wear can grow corners. | Use low-energy finishing and selective metallurgical inspection. |
How This Material Behaves
Invar 36 is a low-expansion iron-nickel alloy whose value depends on dimensional stability. In EDM, this means residual stress release and uneven thermal history can move precision features even when cutting force is absent. Rough symmetrically, allow the part and dielectric to reach thermal equilibrium before final passes, and inspect at the specified temperature and datum condition. For Small Hole EDM, residual stress and asymmetric stock removal can undermine the low-expansion design intent. In deep holes, pressure loss and electrode wear must be evaluated with exit diameter, wall recast and crack-sensitive service requirements.
Surface Integrity and Post-Process
For Small Hole EDM on Invar 36, use lower-energy finishing and inspect critical surfaces when fatigue, sealing or corrosion performance is specified. Reduce discharge energy near final size and breakthrough, then evaluate entry, exit, taper and wall condition separately. For fatigue-, flow- or seal-critical holes, specify recast acceptance or post-process cleaning and finishing instead of relying on diameter alone.
Invar 36 Small Hole EDM Checkpoints
- Confirm that the feature matches small through holes, deep holes, angled holes, cooling holes, vent holes, and start holes in hard or heat-resistant alloys.
- State the supplied condition: solution annealed and cold-worked or stabilized.
- Mark the controlled dimensions, functional surfaces, datum scheme, and inspection method.
Typical Parts and Features
- turbine and energy features
- corrosion-resistant inserts
- precision seals
- turbine-blade cooling holes
- mold and die vent holes
- injector and nozzle holes
Limits and Better Alternatives
Main Limit
Hole depth, diameter, aspect ratio, flushing, and breakthrough quality—not stock thickness alone—set the practical limit. On Invar 36, residual stress and asymmetric stock removal can undermine the low-expansion design intent; the supplied condition still controls support, finishing, and surface-integrity review.
Consider Another Route When
Use mechanical drilling when the tool can reach economically, laser drilling for suitable thin geometry, or Micro EDM for smaller precision holes.
Practical Next Step
Send the Invar 36 drawing with condition, controlled geometry, tolerance, functional surface callouts, quantity, and inspection requirements. If the route is unclear, we will compare Small Hole EDM with the adjacent EDM or conventional process.
Practical Takeaway
Invar 36 is compatible with Small Hole EDM when the feature matches the process access. The supplied condition determines support, finishing, surface control, and inspection.
Additional Project Information
Include application, destination and end-use notes together with the material, quantity and drawing requirements.
Project Details for Technical Review
Include application and end-use notes when they affect material, inspection, documentation, or export review.
- Process: Small Hole EDM
- Material: Invar 36
- Drawing or part sketch
- Material grade
- Thickness / part size
- Quantity
- Tolerance and critical dimensions
- Surface finish or inspection requirement
STEP/STP, DXF, DWG, PDF, IGS/IGES or ZIP.
Confidential drawing review. NDA support available on request.
Frequently Asked Questions
Can Invar 36 be machined with Small Hole EDM?
Yes, when the feature is a small, deep, angled, cooling, vent, or start hole in conductive material. Invar 36 is electrically conductive and the final route follows the feature geometry and supplied condition.
What controls Small Hole EDM on Invar 36?
The main process controls are electrode diameter, true hole depth, depth-to-diameter ratio, tubular-electrode wear, flushing pressure, breakthrough quality, and hole-wall inspection. The Invar 36 condition adds dimensional-stability and surface-integrity requirements.
What is the main risk?
For Small Hole EDM, residual stress and asymmetric stock removal can undermine the low-expansion design intent. The far end of the hole can drift even when the entry diameter and start position remain stable during the final portion of a high-aspect-ratio hole; acceptance must focus on temperature-sensitive datums and low-expansion geometry. On Invar 36, the resulting defect can be position or taper error that is masked until the part and inspection system stabilize thermally. For Invar 36, stabilize workpiece and inspection temperature, finish from controlled datums, and measure only after the part has thermally settled. Inspect entry, exit, taper, position and wall condition independently; document stabilized geometry, datum relationship and inspection temperature for Invar 36.
What should I send for review?
Send the drawing, exact Invar 36 condition, controlled geometry, tolerance, functional surface requirements, quantity, and inspection expectations. If any item is undecided, send what you have and we will help complete the review.