3 · Lead‑in / Lead‑out iEngage: Z plunges to depth while offset by this amount in X (clear of the spinning stock), then X sweeps in to X0 — that's where the A/Y spiral starts. Retract mirrors it. Offset side follows thread hand automatically (flip "Reverse lead direction" in Advanced if it swings the wrong way).
4 · Passes & Depth
iTwo extra passes at final depth, each evaluated at a phase shift along the same helix (not a sideways offset) so the tool traces the true root‑flat/flank boundary — one flank per pass, for a sharp‑point tool. Defaults to P/8 (half the standard root flat width) whenever pitch changes — edit it directly to override.
iA sharp point can't cut a flat root in one pass. These stay at the same final depth as the flank passes but step across in phase (evenly spaced, centered on the true root), clearing the flat between the two flanks instead of leaving a pointed groove. Automatically capped so they never reach past the flank passes.
5 · Feed iThreading blocks use G93 inverse‑time feed so the rotary (deg) and linear (length) axes stay perfectly synchronized regardless of units mismatch. Axial feed rate is the effective travel speed along the thread axis.
6 · Stock Roughing (optional) iClears the raw stock down to the thread's major Ø using a rotating end mill, before threading begins, with the same rotary+linear synchronized spiral as the thread cut but a much finer "lead" set by bit diameter and stepover. Switch to the "Roughing" tab in the G‑Code window to view/copy/download it.
Advanced — machine axis mapping
G‑Code Output
The Thread and Roughing programs, regenerated live as you change any step. Copy them or download a .nc file.
0 lines
Stock
Roughing spiral
Final spiral
Flank finishing pass
Root-clearing pass
Cutter profile (section view)
Section cut face
Tangential engage / retract
Stock roughing (toggle below)
1 · Thread Standard
Computed valuesi
2 · Cutter — Disc Undercutter iA disc-shaped single-form cutter with a known outer diameter and face height, spinning on the vertical spindle like a normal end mill. Its OUTER EDGE does the cutting, so the commanded tool-center path is offset inward from the true thread radius by the disc radius. Disc face height plays the same role external "blunt tip" compensation does — the flank pass phase pulls inward by half the height so the disc's edge, not its centerline, lands on the true flank. Cutters are always specified in millimetres, regardless of the program/display unit used everywhere else. The disc also has to physically pass down through the pre-bored hole (~minor Ø) to reach depth — minor Ø needs to be at least 10% larger than the disc diameter for clearance.
Overall disc thickness iThe disc's full body height — where the tapered flanks meet the solid body — worked out from diameter, face height, and thread angle using the same taper geometry as the 3D/section preview. This is the actual overall thickness of the tool, wider than the face height itself.—
3 · Thread Length (along Z) iThese two Z values bound the thread — End Z must be positive. Spindle only turns CW, so which one is actually the entry point is dictated by the Climb/Conventional choice below — not necessarily the one typed into "Start Z". The tool auto-picks entry vs. exit to match.
4 · Radial Engage / Disengage iThe tool plunges down the bore on-center (always clear — nothing to hit) to Start Z, then sweeps out along a small arc that's tangent to the main helix at the moment of first contact — no perpendicular plunge into the wall, no witness mark. Disengage mirrors it, then the tool returns to center and retracts up the bore.
5 · Passes & Depth iInternal threads cut the opposite way from external ones: the crest (minor Ø) sits at the original bore surface and is left alone, while the root (major Ø) is cut progressively deeper outward into the wall. Each pass here steps the radius outward, finishing at major Ø.
Depth per pass (radial)—
iTwo extra passes at full depth (major Ø / root) by default, each evaluated at a phase shift along the same helix (not a spatial offset) so the disc's edge traces the true root-flat/flank boundary — one flank per pass. Defaults to the root half-flat width (P/8 for 60° V) whenever pitch changes — edit directly to override. Automatically pulled inward by half the disc face height (Card 2). See the option below to step each flank through multiple radii instead of just one.
iBecause the cutter's edge is a flat land with angled flanks rising from it (not a sharp point), a single flank pass at full depth only lands the angled surface near the root — the rest of the flank, up toward the crest, never gets touched. Turning this on repeats each flank side at every radius the initial rough/final passes already step through, so the angled flank surface progressively cleans the whole wall, not just the bottom of it.
iThe disc's flat can't clear a wide root band in one pass if it's narrower than the flat itself. These stay at the same full depth (major Ø) as the flank passes but step across in phase, evenly spaced and centered on the true root — clamped so they never reach past the flank passes.
6 · Feed iThe helical cut uses ordinary G2/G3 circular interpolation synchronized with Z in a single block per revolution — a standard feed rate (length/min) applies directly along the path. No inverse-time feed or rotary-axis sync needed.
7 · Bore Pre‑Roughing (optional) iOpens up a smaller pre-drilled pilot hole toward the thread's minor Ø using a rotating end mill, before thread milling begins — the same helical G2/G3 spiral as the thread cut, but with a much finer axial lead set by bit diameter and axial overlap %, stepping the radius outward pass by pass via the radial stepover. Switch to the "Roughing" tab in the G‑Code window to view/copy/download it.
Advanced — spindle, orbit & datum
Manual override, independent of the Climb/Conventional choice, if the computed G2/G3 sense still swings the wrong way in practice on your setup.
G‑Code Output
The Thread and Roughing programs, regenerated live as you change any step. Copy them or download a .nc file.