Enter Turning Data
Example Data Table
These sample values show how different materials and diameters affect spindle speed and feed speed.
| Material | Diameter | Cutting Speed | Feed | Estimated RPM | Feed Speed |
|---|---|---|---|---|---|
| Mild steel | 50 mm | 180 m/min | 0.20 mm/rev | 1,146 RPM | 229 mm/min |
| Aluminum | 40 mm | 350 m/min | 0.25 mm/rev | 2,785 RPM | 696 mm/min |
| Stainless steel | 2 in | 300 SFM | 0.008 in/rev | 573 RPM | 4.58 in/min |
Formula Used
Metric spindle speed: RPM = (1000 × Vc) ÷ (π × D)
Imperial spindle speed: RPM = (12 × SFM) ÷ (π × D)
Feed speed: Feed speed = RPM × feed per revolution
Machining time: Time = (cut length + approach) ÷ feed speed
Material removal rate: MRR = cutting speed × feed × depth of cut
Power estimate: Power kW = Kc × MRR(mm³/min) ÷ 60,000,000
Tool life estimate: T = (C ÷ V)^(1/n)
These formulas use standard turning relationships. Real results can vary because tools, coolant, machine rigidity, insert grade, and work holding can change cutting behavior.
How to Use This Calculator
- Select metric or imperial units.
- Enter the work diameter and recommended cutting speed.
- Add feed per revolution, cut length, approach, and depth of cut.
- Enter passes, part quantity, and machine efficiency.
- Use manual RPM only when a fixed spindle speed is required.
- Press calculate to view results above the form.
- Download the CSV or PDF report for shop records.
Turning Speed and Feed Guide
Physics of the Cut
Turning connects rotational motion, linear feed, and cutting force. A workpiece spins while a tool advances along its axis. The edge removes a helical ribbon of metal. Good speed and feed settings keep this action stable. They also protect the tool, spindle, and surface finish.
Cutting speed describes how fast the work surface passes the tool. It is measured at the outside diameter. A larger diameter reaches the same surface speed at lower RPM. A smaller diameter needs more RPM. This is why speed must change as diameter changes. The calculator uses the standard lathe relation between diameter, surface speed, and spindle speed.
Feed, Depth, and Load
Feed per revolution controls how far the tool moves during one turn. Higher feed removes more material per minute. It also increases cutting load and roughness. Lower feed gives a finer finish, but cycle time becomes longer. The feed rate is found by multiplying feed per revolution by RPM. This gives the carriage travel each minute.
Depth of cut is another key variable. A deeper cut raises material removal rate. It also needs more power. The calculator combines cutting speed, feed, and depth to estimate removal volume. Specific cutting force is then used to estimate cutting power. This is useful when comparing a job with machine capacity.
Time and Practical Control
Machining time depends on the real travel length. Approach and overtravel should be included. Multiple passes and part quantity also matter. Shop efficiency adjusts the answer for normal delays. These delays can include loading, measuring, chip clearing, and tool checks.
The results should not replace shop judgment. Material grade, insert geometry, coolant, rigidity, and work holding can change the safe range. Start with conservative values when the setup is new. Increase speed or feed only after checking chips, sound, temperature, and finish.
A balanced setup improves productivity. The best values are not always the fastest values. Stable cutting often gives longer tool life and better part quality. Use the graph to compare RPM, feed rate, time, and removal rate. Export the report when you need a record for planning, quoting, or process improvement. Review each output against the toolmaker chart before releasing the job to regular production runs safely daily.
FAQs
1. What is turning speed?
Turning speed is the surface speed of the rotating workpiece at the cutting point. It is usually entered as meters per minute or surface feet per minute.
2. What is feed per revolution?
Feed per revolution is the distance the tool advances during one spindle turn. It affects chip size, finish, cutting load, and cycle time.
3. Why does diameter change RPM?
A larger diameter travels farther in one revolution. It needs fewer revolutions to reach the same surface speed. Smaller diameters need higher RPM.
4. Can I use a manual RPM?
Yes. Enter a manual RPM override when the machine has fixed speeds or when a setup sheet requires a chosen spindle speed.
5. What does machine efficiency mean?
Machine efficiency adjusts cutting time for normal shop losses. It can include measuring, loading, unloading, chip clearing, and short operator delays.
6. Is the power estimate exact?
No. It is an estimate based on specific cutting force and removal rate. Tool shape, wear, coolant, and rigidity can change real power.
7. What is ideal surface finish?
It is a theoretical feed mark estimate from feed and nose radius. Actual finish also depends on vibration, tool wear, material, and coolant.
8. Should I always use the highest speed?
No. Higher speed may reduce time, but it can increase heat and tool wear. Use stable values recommended for the tool and material.