A changing diameter creates different speed histories under two spindle-control modes.
Identify the active control mode
Haas distinguishes diameter-dependent constant surface speed from fixed spindle RPM. Its constant-surface-speed description also identifies the separate maximum-RPM constraint. Primary reference: Haas control explanation.
Trace an invented diameter change
Imagine a fictional turning trace beginning at 80 mm diameter and 500 RPM. Its surface speed is about 125.66 m/min. When diameter becomes 40 mm, fixed 500 RPM gives about 62.83 m/min, while an ideal constant-surface-speed calculation requests 1,000 RPM.
Now assign an invented ceiling of 800 RPM solely for the control comparison. At 40 mm, the limited response gives about 100.53 m/min. The ceiling means the commanded surface-speed target is no longer maintained there. This is a hypothetical mode trace, not an executable program or a proposed chuck speed.
Review target and achieved states
Create columns for diameter at the tool, selected mode, surface-speed target, requested RPM, limiting state and measured RPM. Keep the controller interpretation and units with the actual program under review.
Compare the achieved trace with the target before claiming speed remained constant. Machine, workholding and tooling constraints require their own approved limits; these invented numbers supply none. The useful result is identifying when a control mode changes the speed request and when a separate constraint changes the achieved motion.
Customer Questions
Does fixed RPM hold surface speed as diameter changes?
Its surface speed changes with diameter.
What limits the invented second response?
The expressly assumed 800-RPM ceiling.
Is this a ready-to-run program?
It is a mode-comparison trace.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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