Feed Per Tooth Calculator
Convert feed rate, spindle speed, flute count, radial engagement, chip thinning, material, cutter diameter, axial depth, and roughing or finishing intent into a practical chip load and feed recommendation.
⚙ Machining Presets
Pick a realistic starting point, then adjust feed, RPM, flutes, stepover, material, and tool diameter for your machine and cutter.
📐 Feed And Tool Inputs
Calculation Breakdown
🔧 Material And Tool Grid
📊 Feed Per Tooth Formula Reference
| What To Find | Formula | Imperial Units | Metric Units |
|---|---|---|---|
| Feed per tooth | Fz = feed / (RPM × teeth) | in/tooth from IPM | mm/tooth from mm/min |
| Feed rate | Feed = RPM × teeth × Fz | IPM | mm/min |
| Surface speed | Speed = π × D × RPM | SFM = πDRPM / 12 | m/min = πDRPM / 1000 |
| MRR | MRR = radial × axial × feed | in³/min | cm³/min |
⚒ Starting Chip Load Table
| Material | Small Cutter Under 1/4 in / 6 mm | Medium Cutter 1/4 to 1/2 in / 6 to 12 mm | Notes |
|---|---|---|---|
| Aluminum 6061 / 7075 | 0.0015 to 0.0030 in/tooth | 0.0030 to 0.0060 in/tooth | Use polished flutes and strong chip evacuation. |
| Mild steel | 0.0008 to 0.0018 in/tooth | 0.0015 to 0.0030 in/tooth | Listen for rubbing at very low chip loads. |
| Stainless steel | 0.0006 to 0.0012 in/tooth | 0.0010 to 0.0022 in/tooth | Keep feed positive to reduce work hardening. |
| Acrylic / plastics | 0.0020 to 0.0040 in/tooth | 0.0040 to 0.0080 in/tooth | Sharp O-flute tools help avoid melting. |
📏 Radial Chip Thinning Guide
| Radial Engagement | Typical Factor | Use Case | Feed Per Tooth Meaning |
|---|---|---|---|
| 50% D or more | 1.00x | Slotting, heavy profiling | Programmed Fz is close to chip thickness. |
| 30% D | 1.09x | General side milling | Slight feed increase maintains chip thickness. |
| 15% D | 1.40x | Adaptive roughing | Programmed Fz may need a clear increase. |
| 5% D | 2.29x | Light finishing, rest machining | Check runout before chasing full correction. |
🛠 Tool And Operation Reference
| Tool / Operation | Common Flutes | Chip Load Bias | What To Watch |
|---|---|---|---|
| Carbide end mill roughing | 2 to 5 | 100% to 130% of base | Power, deflection, chip evacuation, and coolant. |
| Finishing side pass | 2 to 6 | 55% to 75% of base | Runout can dominate tiny chip loads. |
| Router O-flute plastic | 1 to 2 | High chip load | Too little feed can melt chips back into the cut. |
| Face mill or shell mill | 4 to 8 inserts | Per insert tooth load | Use engaged inserts and machine horsepower limits. |
💡 Practical Feed Tips
Feed per tooth are the most important measurement in a milling program. Feed per tooth will tell you whether or not the cutter is cutting the material or if it is rubbing against the material. Many different variable will affect the feed per tooth value, but all of those variables will eventually result in a single value of feed per tooth.
If the thickness of the chip is too thin, the cutting edge of the cutter will heat up the material and work hardens it, resulting in a poor surface finish of the milled part. If the thickness of the chip is too thick, the cutting edge will chip or the tool will deflect from the work. Therefore, the chip thickness need to be evened between these two problems, as the correct chip thickness will determine the length of time that the cutter will last during the milling operation, as well as the cleanliness of the milled part.
How to set the right feed per tooth
The inputs to the calculator will take the language of the machine and correlate it to the feed per tooth value. The feed rate and the RPM will be two of the main inputs that will determine the feed per tooth. The flute count, diameter, and radial engagement will allow the calculator to determine whether the milling operation will be a full slot or a side pass.
The axial depth will be another of the inputs that will factor into the feed per tooth calculation. Finally, the material choice, tool type, and cutting mode will all be used as further inputs into determine the feed per tooth. The rigidity and runout of the machine will also factor into the calculation of feed per tooth.
Chip thinning is a concept that those who is learning about the milling process often missed. When the radial engagement is less than half of the cutter’s diameter, the cutter is not able to fully cut into the workpiece. Because the cutter is not cutting a full arc of the workpiece, the thickness of the chip will be thinner than the programmed feed per tooth.
The calculator accounts for this so that users can enter a higher feed per tooth into the machine so that the chip will still be of the thickness necessary for the workpiece being milled. Because of the chip thinning process, adaptive toolpaths can run at faster feed rates with the same RPM as the side milling operations. The chip thinning factor quickly increases when the radial engagement drop below 15% of the cutter’s diameter.
Thus, the same cutter and the same material can require different setting for the feed per tooth from operation to operation. While the recommended feed per tooth is based off the ideal machine rigidity, most shop machines does not have the rigidity to allow for the recommended feed per tooth. Factors like long stickout, worn collet, or light router frame will all reduce the load on the cutter.
The calculator allows for the rigidity of the machine to be entered into the calculator so that the feed per tooth recommendation can be reduced to allow for the machine to still function within its capabilities. In rare case, the shop may have a particularly rigid production machine with a short stickout. In these instances, it may be possible to increase the feed per tooth above the recommended value.
The sound of the cutter and the load on the spindle will change the first time a toolpath is milled at the feed per tooth that has been adjusted. The surface speed of the cutter is another of the factors that is worked into the background of the calculation. Too low of an RPM will cause the cutter to rub against the workpiece.
Too high of an RPM will cause the tool coating to break down and for chip to weld to the rake face of the cutter. The calculated value of the surface feet per minute will display for review by the operator. This value can help the operator to ensure that the chosen RPM is within the normal range for the material that is being milled.
If the surface speed is outside of the normal range for the material, the status line will flag the error so as to not make assumption regarding the cause of the error. The material removal rate will be displayed within the results of the calculator. The material removal rate will allow the operator to ensure that the feed per tooth value is within the capabilities of the machine.
A high feed per tooth is useless if the spindle cannot maintain the RPM or if the coolant system cannot properly remove the chip from the cut. The reference tables will be of most use to those who is purchasing a new cutter or a new material for their machines. These tables will indicate the feed per tooth for various cutter diameters and operations.
These tables are not rules to the milling operation, but they do provide a range of feed per tooth values that have been proven to be safe for use in a milling operation. These tables provide a starting point for those who are relatively new to milling operations. Finally, the safety note at the bottom of the tooling selection will always be a requirement.
As long as the cutter is properly gripping the cutter, the workpiece is properly held in place, and the machine has the power to perform at the rate that is programmed into the machine, the settings will be safe to use. Should any of these factors be uncertain, it is always best to reduce the feed per tooth to half of the recommended value and to test the cutting process on a sample piece of workpiece material. The first cut will reveal whether or not the feed per tooth setting that the calculator recommended was the correct setting for that specific machine and material.
