02.6 · Machining Parameters
Parameter Relationship Map
The three cutting conditions (speed, feed, depth) do not act independently. Changing one ripples through tool life, surface finish, power, and cycle time. This page maps those relationships so you can make trade-offs deliberately.
The Relationship Map
Quick Reference: What Happens If You...
| Action | Tool life | Finish | Power | Cycle time |
|---|---|---|---|---|
| Increase speed 20% | ↓↓ 40–50% | ↑ better | ↑ 20% | ↓ 17% |
| Increase feed 20% | ↓ ~10% | ↓ slightly | ↑ 20% | ↓ 17% |
| Increase depth 50% | ↓ ~5% | ≈ same | ↑↑ 50% | ↓ 33% |
| Use bigger tool nose radius | ≈ same | ↑ much better | ↑ slightly | ≈ same |
The Optimization Ladder
When you want to remove material faster, adjust in this order (least tool life penalty first):
- Increase depth of cut — almost free in tool life.
- Increase feed — small penalty, big productivity gain.
- Increase speed — big tool life penalty, use only when needed.
Real example: a shop was finishing 4140 steel at Vc=200 m/min, f=0.1 mm/rev, changing inserts every 2 hours. They dropped Vc to 150 m/min and increased f to 0.15 mm/rev. Tool life tripled to 6 hours, surface finish stayed the same, and cycle time barely changed. Slower speed + higher feed = better economy.