PRODUCT DATA
■ Guaranteed Range of Retention Diameter Precision Retention diameter (D) Guaranteed precision range Length (e)
■ Step R and Concentricity of Stepped Ejector Pins
Step R
Retention Diameter (D) Tolerance
d 1 Precision
x 1 max.
M Material
Head Thickness (T)
e
a
x 1
10 30 35 40 40 40 30
T4 (EHYF/C–EHYF/EVSL/EVSF)
a ± 3
T4 (4mm)
SKH51
P D
（ L － N ）
JIS (6/8mm)
－ 5 0
N
T4 (4mm)
L
N
SKD61 + Nitriding
JIS (6/8mm) T10 (10mm)
0 –0.02
0 –0.01
d 1 = D
D
In order to ensure the effective dimensions of the length (L–N) of the tip diameter (P), (L–N) is designed to be a plus tolerance and N is a minus tolerance. Step R is configured to form a smooth transition between tip diameter (P) and retention diameter (D). Size of step R: approximately R8–12 ＊ ＊ The size of step R is determined by the size of the grindstone used to process it. This is not a guaranteed value for R. Formula used for calculating the length (a) of step R:
SKD61
T4 (4mm)
e ≧ N–5–x 1 max.–a–3 ＊ 5: Tolerance of length of N ＊ a: Length of Step R section ＊ 3: Tolerance of Step R section length
SKD61 Prehardened
JIS (4/6/8mm)
35
T4 (4mm)
30
■ Guaranteed Range of Base Material Hardness
SUS440C
JIS (6/8mm) 35 E Guaranteed range of SKH51 + Hard chromate plating precision is equal to SKH51.
x 2
b 2 (Guaranteed range of base material hardness)
D−P 2
D−P 2
a =
× (2R–
) Concentricity of Tip diameter (P) and Retention diameter (D): 0.2mm or less
T ＋ 2
■ Finishing of Tips and Edges
Head area annealing
① ②
③
L
b 2 ≧ L–x 2 max.
When ejector pins and core pins are processed to determine the total length, fine processing burring about 0.02–0.05mm (reference values) occurs at the edge of the tip. When this burring is removed, a slight sag occurs.
Base material hardness
Head Thickness (T) x 2 max.
M Material
③ (Guaranteed range of base material hardness)
①
②
T4 ( EHYF EVSG EVSL EVSF )
MISUMI does not deburr the tip in order to prevent sagging.
58–60HRC Overall quenching (no annealing)
58–60HRC Overall quenching (no annealing)
0
58–60HRC
※ SKH51
The allowable sag R at the tip of the pin depends on a variety of conditions such as precision of individual mold, characteristics of the formed object, various shape and resin type. For this reason, the sag R caused by deburring may be an issue. Use an oilstone, sandpaper, cloth, etc. to remove the burring according the precision control standards on your design drawing of the mold being used.
T4 (4mm)
30 35 40 40
28–35HRC (reference value)
28–60HRC (reference value)
58–60HRC
JIS (6/8mm)
T4 (4mm)
28–45HRC (reference value) (Excluding nitrided surface) 28–43HRC (reference value) (Excluding nitrided surface) 28–45HRC (reference value) 28–45HRC (reference value)
28–45HRC (reference value) (Excluding nitrided surface) 28–43HRC (reference value) (Excluding nitrided surface) 28–55HRC (reference value) 28–45HRC (reference value)
40–45HRC (Excluding nitrided surface) 40–43HRC (Excluding nitrided surface)
SKD61 + Nitrid- ing
JIS (6/8mm)
T10 (10mm)
40
SKD61
T4 (4mm)
30 35 30
50–55HRC 40–45HRC
SKD61 Prehardened
JIS (6/8mm)
T4 (4mm) JIS (6mm)
SUS440C
26–35HRC (reference value)
26–60HRC (reference value)
56–60HRC
35 • Annealing is performed on the heads of SKH51 SUS440C SKD61 to achieve a level of 30HRC. Annealing is performed on heads of SKD61 + Nitriding SKD61 Prehardened to achieve a level of 40HRC. ■ Guaranteed Range of Nitriding and Surface Hardness
● Nitriding Nitriding is one of the steel surface treatment methods. The steel is placed in a furnace filled with nitrogen gas, and at high temperature (around 500 ℃ ), a hardened layer combined with the nitrogen is formed on the surface of the steel. ● Nitrided Depth This refers to the depth of the hardened layer formed by the nitriding treatment.
※ Cross–sectional view
b 3 (Guaranteed range of nitriding and surface hardness)
x 3 （＊ x 3 ＝ N ）
①
②
N
The nitrided depth of MISUMI's Hardness of 900HV– plastic mold ejector pin is 0.003–0.008mm (reference value), whereas steel is usually hardened 0.1mm depth (reference value) from the surface by the com- bination with nitrogen. The nitrided depth of straight ejector pin is controlled by adjusting nitriding temperature and treatment time in accordance with shaft diameter size. In the case of stepped ejector pins, nitrided depth is controlled by adjusting nitriding temperature and treatment time in accordance with tip diameter (P) size. For this reason, the surface hardness of the retention diameter (D) of stepped ejector pins is slightly lower, around 500HV (reference value).
L
b 3 ≧ L−x 3 ( ＊ x 3 = N)
Surface hardness
Head Thickness (T)
M Material
x 3 max.
② (Guaranteed range of nitrided surface hardness)
①
Base material hardness
T4 (4mm)
40
(without nitrided layer)
SKD61 + Nitriding
JIS (6/8mm)
40
900HV–
(with nitrided layer)
T10 (10mm)
40
900HV–
97
98
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