Free calculator, no sign-up
Cutting speed and RPM calculator: feed rate and tap drill
Spindle rpm from cutting speed and tool diameter, milling feed rate Vf = n·z·fz, and the tap drill for metric threads M3 to M39. Free, instant result.
- Instant result
- Formula and standards shown
- On desktop and phone
Result
3,183.1rpmSpindle speed n
- Feed rate Vf
- 636.6mm/min
Free during the beta, no credit card
How do you calculate spindle speed (RPM)?
Divide the cutting speed by the circumference of the tool or the workpiece: n = 1,000 × Vc / (π × D), with n in revolutions per minute, Vc in metres per minute and D in millimetres. The cutting speed Vc comes from the tool manufacturer, for a given work material and tool grade; D is the diameter of the drill or cutter, or of the part when turning.
In a maintenance workshop, where the same person sets up a pillar drill in the morning and a lathe in the afternoon, the formula prevents two costly mistakes: a large drill run too fast, which burns its cutting edges, and a small one run too slowly, which wastes time and spoils the finish. For the 12 mm carbide end mill of the example at 120 m/min, the spindle turns at about 3,180 rpm and, with four flutes at 0.05 mm per tooth, feeds at about 637 mm/min.
ISO 513 material groups
Tool catalogues sort cutting speeds by group: P for steel, M for stainless steel, K for cast iron, N for non-ferrous metals, S for heat-resistant alloys and titanium, H for hardened materials.
Turning: the diameter of the part
On a lathe, D is the diameter being cut, and it shrinks pass after pass. On a manual lathe, reset the speed when the diameter changes a lot.
From feed per tooth to feed rate
A milling cutter feed is given per tooth, fz. The table feed is Vf = n × z × fz, so at the same speed a four-flute cutter feeds twice as fast as a two-flute one.
Tap drill: d minus P
For a metric thread, the tap drill is close to the nominal diameter minus the pitch: an M10 × 1.5 thread needs an 8.5 mm drill (ISO 2306).
Reference documents : ISO 513, Classification of hard cutting materials (P, M, K, N, S, H groups) ; ISO 2306, Drills for use prior to tapping screw threads
Machining settings attached to the rework order
Here, the calculator is free and the result is gone when you close the page. In Reglova, it is attached to the work order on the right machine: you find it again at the next breakdown, and on audit day.
The CMMS software comparison, our gaps included- Attached to the work order with its inputs: the server recalculates it, it stays verifiable.
- On the technician's phone, even without a network.
- In the machine's history, for the next breakdown.
When to calculate spindle speed and feed
01
Set up a pillar drill, a lathe or a milling machine to rework a part.
02
Find the tap drill for an M12 × 1.25 without a chart.
03
Compare a carbide tool and a high-speed steel tool on the same part.
Good to know
Cutting speed depends on the material, the tool and the coolant: always start from the tool manufacturer's value.
Spindle speed formula, feed rate and tap drill
Three calculations for the maintenance workshop: the spindle speed n = 1,000·Vc/(π·D) from the cutting speed given by the tool manufacturer, the feed rate of a milling cutter Vf = n·z·fz, and the drill to use before tapping a metric thread.
Formula · Reference documents
n = 1,000·Vc/(π·D) ; Vf = n·z·fz ; tap drill = d − P
Machining: ISO 513 (manufacturers' cutting speeds) ; ISO 2306 (tap drill sizes)
Inputs and accepted ranges
| Input | Unit | Accepted range | Example |
|---|---|---|---|
| Calculation | 3 options | Milling | |
| Tool diameterif Calculation: Spindle speed, Milling | mm | 0.1 to 2,000 | 12 mm |
| Cutting speed Vcif Calculation: Spindle speed, Milling | m/min | 1 to 5,000 | 120 m/min |
| Number of teeth zif Calculation: Milling | 1 to 100 | 4 | |
| Feed per tooth fzif Calculation: Milling | mm | 0.001 to 5 | 0.05 mm |
| Threadif Calculation: Tapping | 34 options |
Calculated results
- Spindle speed nrpm
- Feed rate Vfmm/min
- Theoretical tap drillmm
- Standard drillmm
Workshop rework logged against the machine it serves
- Breakdowns reported by QR code
- Work orders on the phone, even without a network
- Mandatory inspections reminded by email
- Audit file as a PDF, in one click
Free during the beta, no credit card