Lathe - Spindle Speed Variation

Applies to machines built from: 
July, 2013


Spindle Speed Variation (SSV) is control feature that was introduced in software version L6.03.

It lets you vary the spindle speed as defined by (2) settings and M-codes that turn it on and off.

SSV is useful in circumstances where a constant spindle RPM might produce chatter.

For example, when you turn a long shaft down to a small diameter, the machine runs smoothest while the shaft is at its biggest diameter. As the diameter of the workpiece becomes much smaller than its length, the machine can start to chatter. SSV lets you manage the spindle RPM to eliminate the chatter.

SSV is available during turning or boring operations.

It is not available during threading, because the spindle speed must remain constant to produce a good thread.

Codes and Settings



Setting 165, SSV VARIATION (RPM), lets you vary the RPM.

Setting 166, SSV CYCLE (0.1) SECS, lets you set the amount of time, in tenths of a second, that it takes the RPM to vary. A value of 30 in this setting equals 3 seconds.

Sample Program

Before you begin:

  • Make sure that Setting 165, SSV VARIATION (RPM), is set to 100.
  • Make sure that Setting 166, SSV CYCLE (0.1) SECS, is set to 25.

Press MDI.

Type in this code:

G97 S1000 M03

M38 (SSV ON)

G04 P30. (dwell for 30 seconds)


G04 P30. (dwell for 30.seconds)



When the program reaches the M38 command, the RPM rises to 1100 and falls to 900 within 2.5 seconds repeatedly for a period of 30 seconds, as defined by the G04 P30. command.

After the 30-second dwell, the M39 command returns the RPM to 1000 with no fluctuations.

caution: Be sure to give the machine sufficient time to accelerate and decelerate when you change the value in Setting 166. You will induce vibration if the variation cycle time is too short.


The best combination of RPM and time tested to date are:

Setting 165 - 20 RPM

Setting 166 - 30 (3 seconds)


Setting 165 - 30 RPM

Setting 166 - 50 (5 seconds)

Carbide can withstand plus or minus 20 RPM without damaging the insert.

Results will vary based on the tool and workpiece material.

Be aware: Many service and repair procedures should be done only by authorized personnel. The service technicians at your Haas Factory Outlet (HFO) have the training, experience, and are certified to do these tasks safely and correctly. You should not do machine repair or service procedures unless you are qualified and knowledgeable about the processes.

Danger: Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not completely understand. Contact your Haas Factory Outlet (HFO) and schedule a service technician visit if you have any doubts about doing a procedure.