ST/DS/SL - Chuck and Tailstock - Pressure Adjustment Valve - Replacement

Applies to machines built from: 
September, 2013
AD0094 Rev D

ST/DS/SL - Chuck and Tailstock - Pressure Adjustment Valve - Replacement

Parts Included

QTY: 1

Step 1

note: The illustrations show the replacement of the chuck valve. The tailstock valve replacement is the same.
Press POWER OFF. Set the main circuit breaker to the OFF position. Lock the main circuit breaker. Use an approved lock with an approved safety tag.

Remove the valve [1] from the valve block with a crow foot wrench [2]. Before you install the replacement valve, turn the main adjustment knob [3] on the adjustment valve counterclockwise until it stops.

Install the replacement adjustment valve with the crow foot wrench [2]. Leave the screw on the locking jam nut [4] loose.

Unlock and turn on the main circuit breaker. Press POWER ON.
Release EMERGENCY STOP. Press RESET to start the HPU.

Step 2

Refer to the link at the end of the document for the correct pressure. Do not exceed the correct pressure, or permanent damage to the chuck can occur. Slowly raise the pressure of the HPU to the correct maximum value: Turn the main adjustment knob [3] clockwise, check the pressure after each quarter turn. Repeat the process until the HPU is set to the correct pressure. The machine can generate a low pressure alarm until the correct pressure is set.

Turn the locking jam nut [4] clockwise by hand until it stops on the valve body. Rotate the valve and the locking jam nut [4] counterclockwise together until the screw on the locking jam nut [4] is accessible. Tighten the #4-40 thread screw on the locking jam nut [4] to 14 in-lbĀ (1.6 Nm). Hold the locking jam nut [4] while you tighten the screw. Rotate the main adjustment knob [3] clockwise until the locking jam nut stops against the valve body. Make sure that the maximum pressure is correct. If the pressure is not correct, loosen the #4-40 thread screw and rotate the locking jam nut [4] to set the correct pressure.

Set the correct maximum pressure. Go to Chuck and Tailstock - Recommended Maximum Pressure on

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.