TaskJunction › Machine Tools › Lathe Calculator Suite
⚙️ Lathe Turning Operations

Lathe Calculator Suite

Four calculators for everyday lathe work. RPM, feed rate, taper settings, and cycle time. Free, no login required.

mm
Outer diameter at the cutting point
m/min
Recommended Vc from table below
Quick-fill: Common Materials (HSS mid-value)
Enter valid values for both fields.
0 RPM 0 MAX
Spindle Speed (n)
—
RPM
⚙️
Diameter (D)
—
mm
Cutting Speed (Vc)
—
m/min
Verified Peripheral Speed
—
m/min
📐
Formula Used
n = (1000 × Vc) / (π × D)
📊
Recommended Cutting Speeds for Lathe Turning
Material Vc HSS (m/min) Vc Carbide (m/min) Notes
mm/rev
Roughing: 0.2–0.5  |  Finishing: 0.05–0.15
RPM
Use Tool 01 to calculate RPM first
For MRR Calculation (optional)
mm
Roughing: 1–4 mm  |  Finishing: 0.2–0.5 mm
mm
Diameter at cutting point
Enter feed per revolution and spindle speed.
Table Feed Rate (Vf)
—
mm / min
➡️
Material Removal Rate
—
cm³ / min
Feed × RPM check
—
mm / min
📐
Formulas Used
Vf = f × n   (mm/min)
MRR = (π × D × ap × f × n) / 1000   (cm³/min)
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Feed Rate Reference
Roughing: Mild Steel f = 0.25–0.50 mm/rev  |  ap = 2–4 mm
Finishing: Mild Steel f = 0.05–0.15 mm/rev  |  ap = 0.2–0.5 mm
Stainless Steel f = 0.10–0.25 mm/rev  |  Keep tool engaged
Aluminium f = 0.15–0.40 mm/rev  |  High Vc preferred
mm
mm
mm
Tailstock Offset (optional, for between-centers method)
mm
Full length of the workpiece between centres
Enter valid values for the required fields.
Compound Slide Setting
—
degrees (half-angle)
📐
Included Taper Angle
—
degrees
Half Angle
—
degrees
Taper per mm
—
mm / mm
Tailstock Offset
—
mm
📐
Formulas Used
Taper/mm = (D - d) / L
Half angle = atan((D - d) / (2 × L))
Tailstock offset = (Taper/mm / 2) × Total Length
📖
Taper Turning Methods
Compound Slide Method Set the top slide to the half-angle. Good for short tapers and steep angles. Cuts on one axis only, so finish requires care.
Tailstock Offset Method Shift tailstock sideways by the offset value. Good for long gentle tapers between centres. Auto-feed can be used.
Standard Morse Tapers MT1: 1.4287°, MT2: 1.4307°, MT3: 1.4377°, MT4: 1.4876°, MT5: 1.4307°
Taper per mm vs Angle Taper/mm = 2 × tan(half-angle). For small angles, taper/mm is nearly equal to 2 × half-angle in radians.
mm
Length of surface to be machined
mm
Add 3–10 mm for tool entry and exit
mm/rev
RPM
Number of Passes
passes
Roughing passes + 1 finishing pass typically
Enter length, feed per rev and spindle speed.
Total Cycle Time
—
minutes
⏱️
Feed Rate (Vf)
—
mm / min
Time per Pass
—
minutes
Total (m : s)
—
min : sec
📐
Formulas Used
Vf = f × n   (mm/min)
Time/pass = (L + approach) / Vf   (min)
Total = Time/pass × No. of passes
📖
Cycle Time Reference
What is included Actual cutting time only. Add 20–30% for tool change, measurement stops and loading time in a real quote.
Approach and overrun Tool needs room to enter and exit cleanly. Typically add 3–10 mm depending on tool nose radius and setup.
Roughing vs finishing Calculate each pass type separately if feed and RPM differ between roughing and finishing cuts.
Facing operations For face turning, L = (D/2) + overrun. Use constant surface speed (CSS) setting if available on the machine.
👨‍🔧
Vaibhav Dhokpande
Builder, TaskJunction

I built this because I got tired of searching for a simple lathe calculator and ending up on software that wants you to sign up, pay, or install something just to use a formula from a high school textbook.

Most of these tools are not built for engineers in India. They're slow, they're expensive, and half the time they don't even open properly on a phone. Meanwhile the person using it just needs one number so they can set the lathe and get to work.

A formula that has been around for over a century should not sit behind a paywall. That is really what started all of this.

So I made it free. No account. No ads in your face. No "upgrade to unlock" popup. You open it, you type your numbers, you get the answer. That is the whole thing.

This is for the mechanical student finishing an assignment at midnight, the ITI guy on the shop floor who needs a quick check, and everyone in between. If it helped you today, that is enough for me.

If you want a tool that does not exist yet on TaskJunction, just reach out. I am always working on the next one.

Vaibhav
taskjunction.org