FANUC rigid tapping: why feed-per-minute and feed-per-revolution values cannot simply be copied
The 0i-D machining-center manual explains tapping synchronization and feed semantics. Calculations relate thread lead to the two feed modes, with boundaries for overrides, rigid-mode entry and interruption recovery.
Contents
The same F value can represent completely different thread leads in feed-per-minute and feed-per-revolution modes. When transferring a rigid-tapping program, check this semantic difference before optimizing spindle speed.
Reference and scope
This article is based on Section 5.2 of the public mirror of the original FANUC B-64304EN-2/01 manual, for 0i-D / 0i Mate-D machining-center systems configured with the relevant functions. Rigid mode coordinates the spindle and tapping axis so that each revolution corresponds to a specified axial movement. This edition's specific instructions cannot be applied directly to lathes or other generations.
One lead, two meanings of F
Page 76 of the manual distinguishes the two feed definitions. Using metric units, let thread lead be p (mm/rev) and spindle speed n (rev/min):
| Feed mode | Relationship | Unit of F |
|---|---|---|
| Feed per minute | F＝p×n | mm/min |
| Feed per revolution | F＝p | mm/rev |
For an arithmetic check only, assume p＝1 mm/rev and n＝500 rev/min. The two F values are 500 and 1 respectively. They express the same lead; carrying 500 unchanged into feed-per-revolution mode clearly does not preserve the process. This is neither a recommendation to cut at 500 rev/min nor an executable program.
Also distinguish thread pitch from thread lead: they are equal only for a single-start thread. Process inputs must identify the actual tap, thread construction, inch/metric units and program mode.
A cycle number or override setting does not establish the mode
The manual explains that tapping cycles can operate in ordinary or rigid mode. The cycle number alone therefore does not establish the synchronization method. Check rigid-mode entry against the implementation on the particular machine; do not treat any one M code as universal across machines.
Section 5.2.5 also explains that tapping override behavior depends on configuration. Turning down the feed override does not guarantee that the axis and spindle will slow as they would in ordinary motion. Validation must follow the manufacturer's method while maintaining synchronization.
From program review to first-part verification
- Confirm the active units, feed mode and thread lead, and independently recalculate the relationship between F and spindle speed.
- Check effective thread depth, the predrilled hole, tap lead-in and withdrawal clearance, distinguishing drawing requirements from actual travel.
- Check rigid-mode entry, reverse withdrawal and subsequent program states, then validate under the machine's procedure.
If tapping is interrupted with the tap inside the hole, record the cycle stage and alarm and follow that machine's recovery procedure. Do not attempt withdrawal by arbitrary jogging or reversal. First-part verification must cover both thread quality and withdrawal. Return to the OPTION resources.