MTS Series 646 Hydraulic Collet Grips - Manual (Page 57)

Series 646 Hydraulic Collet Grips Operation 57
Installing a Collet for a Threaded Specimen
Important
The 646 Hydraulic Collet grip has a very small amount of grip stroke. Specimen
size and placement is critical to ensure proper specimen preload. Failure to
follow the proper procedure will result in force and displacement disruptions,
premature specimen failure, and possibly grip failure.
1. Put both grips in the fully released position. Place the control valve in the
“release” position with hydraulic power to the load frame. If using a hand-
operated pump, actuate the pump until extra resistance is felt. It should
require approximately 10 strokes of the pump.
2. Unthread the collet adaptor from the grip body by approximately 3/8”
(10mm) for both grips
3. Install the specimen in the grips according to the correct procedure for your
specimen type. Do not apply hydraulic pressure to grip the specimen.
4. Thread the collet adaptor into the grip until the specimen makes contact with
the pushrod. Loosen the collet adaptor approximately 1/8 turn, or just
enough to make a small gap between the specimen and pushrod. The collet
adaptor should not be more than ¼” (6.3mm) above the top of the grip body.
Pressurizing the grip with the collet adaptor more than ¼” (6.3mm) above
the top of the grip may result in grip damage.
5. Pressurize the grip to the appropriate pressure.
Procedure
The threaded insert and collet retainer are installed and removed each time the
specimen is changed.
Pushrod
Collet Adapter
1/4” (6.33 mm)
max when
pressurized