BIZOMAT MAKEOS · Threads
Thread Turning Infeed per Pass
How deep should each pass be when single-point turning this thread?
Radial infeed for each pass of a single-point threading cycle with a decreasing (constant chip area) schedule, with cumulative depth and the X diameter for each pass.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Thread | choice | External or internal thread. |
| Nominal diameter | mm | Nominal thread diameter. |
| Pitch | mm | Thread pitch. |
| Number of passes | passes | Number of cutting passes (tool supplier tables suggest a number for each pitch). |
| Total radial depth (0 = standard) | mm | Total radial depth; 0 uses 0.6134P (external) or 0.5413P (internal), the ISO basic heights. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Thread
- What it is
- Whether the thread is cut on the outside of a part (external, on a screw) or inside a bore (internal, in a nut), for a metric 60° profile.
- Units and format
- Choose one of 2 options from the list: External (metric 60°); Internal (metric 60°).
- Example
- The form opens with “External (metric 60°)” selected as a worked example. Choose the option that matches your case.
- Get it right
- This changes the default depth and whether the X diameters decrease (external) or increase (internal).
What this means: Nominal diameter
- What it is
- The nominal size of the thread, for example 20 for an M20; external X diameters start from it, internal ones from the basic minor diameter.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Pitch
- What it is
- The axial distance between neighbouring crests of the thread being cut, which is also the feed per revolution while threading.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 20 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2.5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The default total depth is proportional to the pitch.
- Get it right
- Enter the pitch, not the lead; for a single-start thread they are the same.
What this means: Number of passes
- What it is
- How many cutting passes the threading cycle takes to reach full depth; the infeed gets smaller with each pass.
- Units and format
- Enter a number in passes: passes. The form accepts 2 passes to 40 passes. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 8 passes as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More passes give smaller infeeds on every pass.
- Get it right
- Tool suppliers give a recommended number of passes for each pitch; follow their table for the insert.
What this means: Total radial depth (0 = standard)
- What it is
- The total radial depth to be cut, from the starting diameter to the finished thread root; zero uses the basic thread height for the selected type.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 50 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Every pass infeed scales in proportion to the total depth.
- Get it right
- Zero means use the standard depth, not zero depth. Enter a value only to override it.
Method and formulas
- First pass: Δ₁ = a_p √0.3 ÷ √(n − 1).
- Cumulative depth after pass x (x ≥ 2) = a_p √(x − 1) ÷ √(n − 1); the last pass reaches a_p.
- External X = d − 2 × depth; internal X = minor diameter + 2 × depth.
- Example: M20 × 2.5 external in 8 passes: first infeed 0.31746 mm, last 0.11375 mm.
Limitations
- Radial depth schedule only; flank or modified-flank infeed changes the X/Z moves.
- Add spring passes as your process requires.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Program a threading cycle by hand
- Choose the number of passes
- Check a G76 depth schedule
Who it is for
- CNC programmers
- Machinists
What you get
- Infeed for each pass
- Cumulative depth
- X diameter for each pass
Interpreting the result
- Keep the last pass above the insert’s minimum infeed (often about 0.05 mm) to avoid rubbing.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2037–2042, 1289–1300. Topic reference; no source tables or recommended settings are reproduced.
BIZOMAT tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.