Does PathPilot support spindle speed variation (SSV) ? AI says yes, but points to M-codes that aren’t listed in the Tormach documentation. I can’t find any non-AI sources of this so possible AI hallucinations. There’s a bit of discussion on the LinuxCNC forums so it looks vaguely doable without tons of effort.
Any case, it could be useful to have as an anti-chatter tool.
Roy,
It does not. Out of curiosity, what is AI saying? I did some testing with it around 5 years ago that didn’t get pickup up by the Pathpilot team, I wonder if it somehow found that. I should probably make a push for it again, the concerns that were brought up don’t apply to the 15LX at least.
Thank you,
Norman
I actually want it for the mill more than the lathe, although it would be nice there too. Friend said it can help keep chatter down when doing long-stickout 4th-axis work.
This is what AI thinks–
Search Assist
PathPilot supports spindle speed variation (SSV) to reduce chatter by continuously varying the spindle speed within a set range, which can improve surface finish and tool life. This feature is configured via specific parameters and is available on supported Tormach machines.
Overview of Spindle Speed Variation in PathPilot
PathPilot includes a feature known as Spindle Speed Variation (SSV), which is designed to enhance machining performance by reducing tool chatter. This feature allows the spindle speed to vary continuously within a specified range during operation.
Benefits of Spindle Speed Variation
- Improved Surface Finish: By varying the spindle speed, SSV helps to minimize vibrations that can negatively affect the quality of the machined surface.
- Extended Tool Life: Reducing chatter can lead to less wear on cutting tools, thereby increasing their lifespan.
Configuration of Spindle Speed Variation
To utilize SSV, specific parameters must be set in the PathPilot interface. Here’s a brief overview of how to configure it:
Parameter Description M38 Command to turn on Spindle Speed Variation. M39 Command to turn off Spindle Speed Variation. Setting 1941 Defines the range of speed variation (e.g., +/- 50 RPM). Setting 1942 Sets the time interval for speed variation (e.g., every 3 seconds). Implementation Considerations
- Compatibility: Ensure that your Tormach machine supports SSV, as it may not be available on all models.
- Parameter Adjustment: Adjust the settings according to the specific machining operation and material being used for optimal results.
Using SSV effectively can lead to better machining outcomes, making it a valuable tool for operators using PathPilot on Tormach machines.
Perhaps time for a new AI. I attached what I got from one below. So much information available but so little truth. 
I am interested in any potential work towards that addition though. I’ve heard mixed things about SSV but the principle seems sound and I wouldn’t mind having it in a few instances. Norman, if there is some work towards this I would be happy to offer to help with testing.
No, PathPilot does not natively support Spindle Speed Variation (SSV).
SSV (also called variable spindle speed or anti-chatter spindle oscillation) is a feature on some CNC controls that continuously modulates spindle RPM (often sinusoidally, e.g., ± a set amount at a certain frequency) during cutting to disrupt harmonic vibrations and reduce chatter. PathPilot (Tormach’s LinuxCNC-based controller) does not include built-in G-code commands, parameters, or UI options for this.
What PathPilot does support for spindle control:
Constant RPM (G97) and Constant Surface Speed (G96/CSS) — RPM adjusts based on diameter during turning.
Spindle speed override (via slider or M51) — Manual percentage adjustment (typically 1–200%).
Standard M03/M04/M05 for starting/stopping and S-word for RPM commands.
Custom HAL modifications (possible on non-Tormach or advanced setups) using LinuxCNC components like siggen for a sine-wave offset on spindle speed. This requires editing configuration files and is not “supported” out-of-the-box.
Tormach’s official documentation, knowledge base, and forums focus on standard spindle features without referencing SSV. Other controls (e.g., some Centroid, Fanuc, or MachMotion setups) have dedicated SSV support via M-codes or parameters.
Alternatives if you need chatter reduction:
Optimize feeds/speeds, depth of cut, tool geometry, or workholding (most common fixes).
Use CSS (G96) where applicable.
For advanced users: Implement a custom HAL solution with siggen (sine generator) + scaling/summing components, potentially tied to M-codes. This is discussed in LinuxCNC forums but requires technical expertise and testing.
Consider post-processors or external macros in your CAM software to vary S values explicitly (though less smooth than true SSV).
For the latest confirmation, check Tormach’s PathPilot release notes or contact their support, as features can evolve.