How to choose the right frequency depth for shafts, gears, and axles.
1. Introduction: Precision Over Power
In the modern heat treatment industry, “hardening” isn’t just about applying heat—it’s about controlling where that heat goes. One of the most common questions we receive at Inductwell is: “Do I need a Medium Frequency or a High Frequency machine?”
The answer lies in the physics of the “Skin Effect.”
If you are looking for a quotation for an Induction Hardening Machine, choosing the wrong frequency can lead to component distortion (if too deep) or insufficient wear resistance (if too shallow). This guide breaks down the technical differences to help you select the right machine for your production line.
2. The Core Difference: Frequency = Depth
The rule of thumb in induction hardening is simple:
- Lower Frequency (Medium) = Deeper Heat Penetration.
- Higher Frequency (High) = Shallower, Surface-Level Heat.
3. Medium Frequency Induction Hardening Machine
- Frequency Range: Typically 1 kHz – 20 kHz
- Hardening Depth: 2mm – 8mm (Deep)
When to choose this: A Medium Frequency Induction Hardening Machine is the workhorse for heavy-duty components. Because the current penetrates deeper into the metal, it is ideal for parts that bear heavy torsional loads and need core strength, not just surface hardness.
- Ideal Applications:
- Large Axle Shafts (Automotive & Trucking).
- Large Gears (hardening the root/base of the teeth).
- Camshafts and Crankshafts.
- Heavy machinery pins.
The Inductwell Advantage: Our Medium Frequency systems are designed with advanced IGBT technology that ensures consistent heating depth, preventing the “brittle core” effect often seen in older thyristor-based machines.
4. High Frequency Induction Hardening Machine
- Frequency Range: Typically 30 kHz – 100 kHz (or higher)
- Hardening Depth: 0.5mm – 2mm (Shallow)
When to choose this: A High Frequency Induction Hardening Machine is a precision tool. It heats the “skin” of the metal so rapidly that the core remains cool and unaffected. This is critical for parts that need a hard, wear-resistant surface but must maintain their original dimensions without warping.
- Ideal Applications:
- Small Gears (hardening the tips/teeth only).
- Automotive Valves and Fasteners.
- Precision Pins and Needles.
- Thin-walled components that would warp under deep heat.
The Inductwell Advantage: Our High Frequency units feature rapid-response tuning, allowing for precise start-stop cycles essential for high-speed automation lines in Faridabad and across India’s auto-hubs.
5. Technical Comparison Table
| Feature | Medium Frequency (MF) | High Frequency (HF) |
| Frequency | 1 – 20 kHz | 30 – 100 kHz+ |
| Depth of Hardness | Deep (2mm+) | Shallow (0.5mm – 1.5mm) |
| Primary Benefit | Torsional Strength | Surface Wear Resistance |
| Distortion Risk | Low (on thick parts) | Very Low (on thin parts) |
| Best For | Axles, Large Shafts | Small Gears, Fasteners |
6. Conclusion: Which Quotation Do You Need?
If your production line handles a variety of parts—ranging from heavy shafts to tiny pins—you may actually need distinct stations for each to maximize efficiency.
At Inductwell, we don’t just send a price list; we engineer the solution.
Next Step: Are you unsure if your component requires deep or shallow hardening? Send us your component drawing or hardening depth specifications along with your request.