Mastering Chip Load (IPT)
The single most important number in machining. Too little = rubbing/heat. Too much = tool breakage.
Calculate Chip Load Instantly
Don't risk your tools. Use our calculator to find the perfect Feed Rate (IPM) based on your desired Chip Load.
What is Chip Load?
Chip Load (also known as Feed Per Tooth or IPT) is the size of the material slice that each cutting edge of the tool removes during one revolution.
It is physically the thickness of the chip.
- Why it matters:
- Too Small: Variations in material/cutter mean the edge rubs instead of cuts. Friction = Heat = Work Hardening.
- Too Large: Cutting forces exceed the strength of the tool or the flute space. Snap!
The Formula
To find Feed Rate (IPM):
IPM = RPM × IPT × Flutes
Standard Chip Load Starting Points (1/2" End Mill)
Values are for a standard 1/2" Carbide End Mill. Scale down for smaller tools (e.g., 1/4" tool = 50% of these values).
| Material | Roughing IPT | Finishing IPT |
|---|---|---|
| Aluminum (6061) | 0.003" - 0.008" | 0.001" - 0.003" |
| Low Carbon Steel (1018) | 0.002" - 0.004" | 0.001" - 0.002" |
| Stainless (304) | 0.0015" - 0.003" | 0.0008" - 0.0015" |
| Titanium (6Al-4V) | 0.002" - 0.004" | 0.001" - 0.002" |
| Plastics (Delrin/ABS) | 0.006" - 0.012" | 0.003" - 0.005" |
Don't Forget Chip Thinning!
If your radial width of cut (stepover) is less than 50% of the cutter diameter, your actual chip load is thinner than calculated.
The Fix: You must increase your feed rate to maintain the target chip thickness.
Read the full explanation in our Feeds & Speeds Guide →Quick Rule of Thumb: Scaling by Diameter
A good starting point for chip load is often based purely on cutter diameter:
Standard Rule (End Mills)
0.5% - 1.0%
of Cutter Diameter
Example: 1/2" Tool * 0.01 = 0.005" IPT
Face Mills
0.005" - 0.020"
Fixed Range
Large inserts can handle heavy loads.