Turning — modes

How to use the calculator

Select the mode: Vc → RPM (set the cutting speed - get the speed) or RPM → Vc (set the speed - get the cutting speed). Enter the workpiece diameter, material and insert type - the calculator will calculate RPM, table feed Vf and MRR productivity. If Vc is not specified, the typical starting value is substituted.

The Intermittent Cut (Groove/Cast/Key) flag activates additional warnings regarding insert geometry selection.

Key turning formulas

RPM = 1000 × Vc / (π × D)

Vf = RPM × f(table feed, mm/min)

MRR ≈ Vc × ap × f (removal capacity, cm³/min)

Where: D - workpiece diameter (mm), Vc - cutting speed (m/min), f - feed (mm/rev), ap - depth of cut (mm).

The values ​​are generalized starting guidelines. Check the plate manufacturer's catalog for your specific brand.

Frequently Asked Questions

What is MRR and why should you know it? Material Removal Rate - cubic centimeters of metal per minute. Shows the performance of the operation. In roughing, the goal is maximum MRR without vibration; when finishing - minimal deviations from the size.

Why is the rigidity of the system important? With weak clamping or a large overhang of the cutter, the permissible ap×f is sharply reduced. If with rigid CNC a load of ap×f = 1.0 mm² is permissible, then with a 4×D overhang the same load will cause vibrations and chipping of the plate.

When to avoid ceramics? Ceramic plates give a high Vc, but are brittle. Interrupted cuts, impact loads, stainless steel and interrupted HRSA are not applications for ceramics. Use carbide with strong geometry (negative rake, CNMG, DNMG).

Turning inserts and holders - WODEX, ALBERG, FRIZZ - in our catalog. We select the geometry and brand for the task.

Select the operation (parting/groove), machine type, enter the part diameter and insert width. Indicate the measured deviation h and its sign (above or below the center). If there is a symptom, choose it: “pip”, cut, vibration or bad end. The calculator will show the tolerance on h, estimate the position and suggest the direction of adjustment.

Why is the center height critical when cutting?

When cutting and grooving, the height of the cutting edge relative to the spindle axis is one of the main parameters. A small deviation, which is almost imperceptible during external turning, becomes critical when approaching the center of the part:

• Below the center (h < 0)—the cutter “dives” under the part at the end of the segment. Result: cut, plate wedge, breakage.
• Above the center above the norm, a “pip” remains in the center, the load increases, and vibrations are possible.
• Ideal position: 0…+0.05 mm (exactly in the center or slightly above). When approaching the axis, the cutting speed tends to zero - a slight excess compensates for the drop in Vc.

Tolerance for h by machine type

On a rigid CNC machine, the permissible deviation h for a standard cutting plate b = 3 mm is ≈ ±0.05 mm. On a universal lathe - ±0.04 mm due to backlash of the support and deflection of the cutter under load. Narrow plates (b ≤ 2 mm) and small diameters (Ø ≤ 20 mm) tighten the requirements by another 0.005–0.010 mm.

How to measure h without an indicator? A quick way is to test cut on a small diameter (Ø 10–20 mm). If there is a “pip” left in the center, the incisor is higher than normal. If the plate wedges at the end - lower. Fine tuning - indicator or measurement using a standard mandrel.

Does the insert width affect the h tolerance? Yes. A wider plate creates more force at the end of the segment - the deflection h is tolerated a little easier. A narrow insert (b ≤ 2 mm) is more sensitive to offset: use a stiffer toolholder and check h more often.

What to do with vibrations at the end of a cut? Vibrations at the end are always a combination of: h, cutter overhang, feed and Vc. Reduce the overhang to a minimum, reduce the feed by 20-30% in the final section, make sure that h is within tolerance. On a universal one, you can bring the bar in with the tailstock quill.

Cutting and groove inserts - WODEX, ALBERG, SCHWANOG - in our catalog.