MTS Axial Extensometers - Manual (Page 32)

Configuration 32
8. Loosely attach the upper knife edge hold-down to the upper
extensometer arm using the two socket head cap screws removed
in Step 5. Ensure that the attachment hook is behind both socket
head cap screws.
9. Repeat Step 7 and Step 8 for the lower arm.
10. Tighten the socket head cap screws only enough to secure the knife
edges.
11. If straight knife edges are being used, place the flat surface of a
machinist’s square or similar object across the face of both knife
edges to ensure that both edges are parallel to each other.
12. Use a small adjustable wrench to grasp the sides of the upper arm.
13. While securely holding the extensometer arm, fully tighten the
socket head cap screws with a hex wrench.
14. Repeat Step 12 and Step 13 to tighten the socket head cap screws
on the lower arm.
How to Change Knife Edges
Knife edges are available in straight or three-point contact sets:
• Straight knife edges are used for testing round specimens.
• Three-point contact knife edges are used for testing flat
specimens. One knife edge has a single point and the other
knife edge has two points.
Note The knife edges for the Series 632 Extensometers and the
Series 634 Extensometers are not interchangeable. The
differences are shown in the following figure.
Straight Knife Edge Three-Point Knife Edge Set
Top
Bottom
634
632
634
632
634
632