Key Points:
- Formula for calculating expected force:
- Expected force (kgf) = Cutting width × Cutting depth / 1 tooth (mm) × Specific cutting resistance (kgf/mm²) × Number of simultaneous cutting teeth.
- Safety load: 1.8 × Expected force (kgf).
Example Calculation:
- Square spline broach: Ø20 × 16 × 4 × NT6
- Heat-resisting steel, cutting length = 25mm
- Pitch = 7.5
- Number of simultaneous cutting teeth = 25 / 7.5 ≈ 3.3–4
- Cutting depth = 25µm
- Expected force: 4 × (6 × 0.025) × 0.4 × 4 = 1 ton
- Safety load = 1.8 × 1 ton = 1.8 ton
Cutting Depth Table:
| Material Type | Round | Spline | Surface |
|---|---|---|---|
| Alloy steel | 10–20 | 25–30 | 30–70 |
| Carbon steel | 10–20 | 25–35 | 50–75 |
| Cast iron | 15–35 | 25–35 | 50–75 |
| Malleable cast iron | 20–35 | 25–35 | 50–75 |
| Light alloy metal | 25–35 | 30–40 | 50–100 |
Broach Cutter Length and Machine Stroke:
- Broach cutter length + Length of rear end shank (Max) = (Max stroke) – (Cutting length).
- Broaching length should be less than machine max stroke.