Process & Material
AZ91 Magnesium Alloy Small Hole EDM Drilling General Tolerance + Mirror / Post-finished EDM Surface Finish Review
This AZ91 Magnesium Alloy Small Hole EDM page combines a General tolerance target with a Mirror / post-finished EDM surface target. These requirements must be planned together because finishing passes improve texture while also changing profile offset, cavity size, hole size, or edge geometry.
Quick Answer
For AZ91 Magnesium Alloy, ±0.025–0.050 mm and Ra 0.1–0.4 μm are achievable on selected Small Hole EDM features when electrode runout, flushing, breakthrough support, and the finishing sequence are planned together. Apply both targets from the same datum, and reserve the tightest values for the dimensions and faces that control function.
Key Quality Decisions
What These Targets Mean
On AZ91 Magnesium Alloy, ±0.025–0.050 mm controls the named dimensions and Ra 0.1–0.4 μm controls the named functional faces. In Small Hole EDM, diameter, straightness, wall condition, and breakthrough respond differently to electrode wear and finishing energy. The supplied condition adds a separate risk: casting porosity, thin walls and surface reactivity can destabilize finish and edge quality.
Getting Both Targets Right
Use one machining and inspection datum. Apply ±0.025–0.050 mm only to dimensions that control fit, and Ra 0.1–0.4 μm only to functional faces. Plan electrode diameter, true path depth, aspect ratio, flushing, rotation, straightness, and breakthrough support. State the exact AZ91 Magnesium Alloy condition and the inspection method before releasing the result.
What Gets Missed
On a deep small hole specified at ±0.025–0.050 mm and Ra 0.1–0.4 μm, entry diameter can pass while exit diameter, straightness, or breakthrough position fails. The tolerance represents a broad size band, while polishing or lapping after EDM removes additional stock and can round edges or dish a face; treating them as independent callouts can make the last finishing step destroy the dimension it is meant to improve. Inspect entry, exit, taper, straightness, and hole-wall condition after the final surface step. For AZ91 Magnesium Alloy, also account for this material-specific risk: casting porosity, thin walls and surface reactivity can destabilize finish and edge quality.
How the Targets Interact
For AZ91 Magnesium Alloy, ±0.025–0.050 mm and Ra 0.1–0.4 μm are linked through the Small Hole EDM finishing route. Diameter, straightness, wall condition, and breakthrough respond differently to electrode wear and finishing energy. The release plan must bind material condition, geometry, datum, finishing stage, and measurement to the same named features.
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. |
Quality Target Reference
| Requirement | Planning range | What it means in practice |
|---|---|---|
| General tolerance | ±0.025–0.050 mm | Use one controlled EDM pass where geometry matters more than close fit. |
| Mirror / post-finished EDM surface finish | Ra 0.1–0.4 μm | Treat this as EDM plus controlled finishing or polishing rather than a default one-pass result. |
Material Condition Reference
| Condition | What to expect | Watch out for | Surface notes |
|---|---|---|---|
| as-cast | Use stable support and economical roughing. | Clamping and material condition can move delicate features. | Apply fine finishing only to functional faces. |
| solution-treated | Balance dimensional stability with feature-specific finishing. | Residual stress can shift thin sections or small details. | Identify wear, seal, fatigue, or contact surfaces. |
| aged condition | Use conservative energy and selective inspection. | Finished or hardened surfaces can be sensitive to edge damage and recast. | Use lower-energy finishing or post-processing where function requires it. |
Tolerance & Surface Requirements
For Small Hole EDM at ±0.025–0.050 mm and Ra 0.1–0.4 μm, apply the finish only to the faces named on the drawing. On AZ91 Magnesium Alloy, avoid unsupported absolute capability claims and define cleaning, residue and handling requirements before production. Roughness does not replace recast, edge, corrosion, crack, or post-process acceptance where those items affect function.
AZ91 Magnesium Alloy Small Hole EDM Quality Checkpoints
- Mark the dimensions that actually need ±0.025–0.050 mm and use the same datum for machining and inspection.
- Circle the faces that need Ra 0.1–0.4 μm; leave nonfunctional surfaces at a practical production finish.
- State the AZ91 Magnesium Alloy condition, Small Hole EDM finishing strategy, measurement method, and any recast or edge requirement.
Limits and Better Alternatives
Main Limit
±0.025–0.050 mm and Ra 0.1–0.4 μm are selected-feature planning references for AZ91 Magnesium Alloy in Small Hole EDM, not unconditional whole-part guarantees.
Consider Another Route When
Use mechanical drilling for accessible easy-cutting material, laser drilling for suitable thin high-volume parts, or Micro EDM for smaller precision features.
Practical Next Step
Send the AZ91 Magnesium Alloy drawing with the Small Hole EDM features that need ±0.025–0.050 mm, the faces that need Ra 0.1–0.4 μm, the supplied condition, quantity, datums, and inspection method.
Practical Takeaway
On AZ91 Magnesium Alloy, plan ±0.025–0.050 mm and Ra 0.1–0.4 μm together for the selected Small Hole EDM features. Use one datum and one inspection plan, and apply the tightest values only where they control function.
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: AZ91 Magnesium Alloy
- 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.