FED-STD-228A
3.1.1.7 Grips.
3.1.1.7.1 Dumbbell specimen. When a dumbbell specimen is used, the grips which hold the specimen in
the testing machine shall be of a type which tightens automatically as the applied tension increases and
exerts a uniform pressure across the gripping surfaces so as to avoid uneven slipping and to favor failure
of the specimen in its constricted section.
3.1.1.7.2 Straight. When a straight specimen is used, either wedged or toggle clamps shall be used.
The distance between the edges of the clamps at the start of the test shall be 3 ± 1/8 inch.
.0156" MIN. GRIND
W +0.001
- 0.000
30° - 35°
L
.25" MIN. GRIND
E
F
B
SPACER
T
18° - 22°
T
A
B
H
ENLARGED DETAIL OF
(radius)
CUTTING EDGE SECTION T-T
G
(radius)
4.5 in.
C + .5" MAX.
A
X
+0.002"
C
W - 0.000"
THREAD THIS
SIDE OF DIE
.375 in.
F
Section X - X
X
2 ALLEN HEAD BOLTS
2 Allen head bolts
Handle for hand dieing of specimen
FIGURE 3021
3.1.2 Dies. Metal dies of the shape and construction shown on figure 3021 and of the dimensions shown
in the accompanying legend shall be used for stamping or cutting of dumbbell specimens. It is
recommended that the reduced section of the die bet equipped throughout its entire length with a spacer
to maintain a definite distance between the cutting edges. The spacers shall be held by at least two bolts
through the body of the die. The difference between the minimum and maximum distance between the
cutting edges of the die in the reduced section shall not exceed 0.002 inch. The inside faces in the
reduced section shall be polished and perpendicular to the plane formed by the cutting edges for a depth
of at least 0.25 inch. The angle between the inner and outer faces at the cutting edge shall be not less
than 30° and not more than 35°. The outer face shall extend at this angle from the cutting edge for
approximately 1/64 inch and then shall form an angle between 18° and 22° with the inner face. The dies
shall be sharp and free from nicks in order to prevent leaving ragged edges on the specimen.
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