How to use this calculator
- Enter the spindle speed. Enter the tapping RPM (n).
- Enter the thread pitch. Enter the thread pitch (P). For inch taps, convert: P = 25.4 ÷ TPI.
- Read the feed rate. Read the feed rate Vf = n × P and the feed per rev (which equals the pitch).
How it works
In tapping, the tap is screwed into the hole and cuts its own thread, so it must
advance exactly one thread pitch for every revolution. That means
the feed per revolution is fixed — it equals the pitch — and the feed rate is locked
to the spindle speed:
Vf = n × P
where n is the spindle speed in RPM and P is the thread
pitch. Unlike drilling or milling, you cannot choose the feed independently: pick the
pitch (it comes with the tap) and the speed, and the feed rate follows.
For inch taps the thread is usually given as threads per inch (TPI),
so convert to a pitch first: P = 25.4 ÷ TPI. Then apply
Vf = n × P exactly as for a metric tap.
Worked example
Verified against the live calculator
A metric tap with a 1.0 mm pitch running at
500 RPM needs a feed rate of
Vf = 500 × 1.0 = 500 mm/min, with a feed per revolution of
1.0 mm — the pitch itself. An inch example: a 1/4-20 tap (20 TPI,
so P = 25.4 ÷ 20 = 1.27 mm) at 800 RPM gives
800 × 1.27 ≈ 1,016 mm/min. The calculator returns these on load.
Frequently asked questions
How do you calculate tapping feed rate?
Tapping feed rate is spindle speed times thread pitch: Vf = n × P. In tapping the tap advances exactly one thread pitch per revolution, so the feed per rev equals the pitch. For example, 500 RPM with a 1.0 mm pitch tap gives Vf = 500 × 1.0 = 500 mm/min.
Why is tapping feed rate locked to the pitch?
The tap cuts its own thread, so it must advance exactly one pitch for every full turn — otherwise it would strip the thread. That makes the feed per revolution equal to the pitch and the feed rate Vf = n × P. Unlike drilling or milling, you cannot pick the feed independently of speed.
How do I find the feed rate for an inch tap?
Convert the threads per inch to a pitch first: P = 25.4 ÷ TPI. A 1/4-20 tap is 20 TPI, so P = 25.4 ÷ 20 = 1.27 mm. Then Vf = n × P — at 800 RPM that is 800 × 1.27 ≈ 1,016 mm/min (about 40 in/min).
What is rigid (synchronized) tapping?
Rigid tapping electronically synchronizes the Z-axis feed to the spindle so the machine itself holds Vf = n × P, in both directions. It needs an encoder-fed spindle and lets you run a solid holder. Without it you use a tension-compression (floating) holder so the tap can self-feed and absorb small sync errors.
Does the feed rate change on retract?
No — the tap unscrews at the same feed per rev, so the reverse feed rate equals the same Vf = n × P. Rigid tapping reverses the spindle and the axis together automatically; a floating holder lets the tap back itself out.
Does this work in metric and imperial?
Yes — enter the pitch in mm or inches and the feed rate is shown in mm/min or in/min. For inch taps given as TPI, convert with P = 25.4 ÷ TPI. Toggle SI/Imperial in the header.
Method & assumptions
- The tap advances exactly one pitch per revolution — feed per rev equals the pitch, so the feed rate is not chosen freely but follows Vf = n × P.
- Rigid (synchronized) tapping drives the Z-axis feed in lockstep with the spindle to hold Vf = n × P precisely, including the reversal on retract. It needs a synchronized spindle and allows a solid holder.
- Tension-compression (floating) holders let the tap self-feed and absorb small synchronization errors when the machine is not rigid-tapping capable; the nominal feed is still Vf = n × P.
- On retract the tap unscrews at the same feed per rev, so the reverse feed rate equals the same Vf.
- For inch taps, convert the pitch first: P = 25.4 ÷ TPI before applying Vf = n × P.