PRODUCT DATA
■ Finishing of Corners of Rectangular Ejector Pins
■ Guaranteed Range of Shaft–diameter Precision Rectangular Ejector Pins
x 1 max.
d 1 Precision
T Retention diameter (D) tolerance
Head thickness (T)
For rectangular ejector pins, P/W dimensions cannot be measured if there is burring, so remove the burring from the corners. As a result, a maximum of 0.03mm of burring R occurs. However, the deburring of edges is not carried out. E This deburring is for measuring the P/W dimensions and may leave some burring.
M Material
D 0
T4 (4mm)
30
–0.02
e
x 1
a 1
d 1 = D
0 –0.1
SKH51
D 0
–0.05
JIS (4/6/8mm)
35
SKD61 equivalent + Nitrided
N
JIS (6/8mm)
40
Corner R value of the tip corner Rmax . Rmax. ≦ 0.03 (deburring R)
4 － R ≦ 0 . 03 (Deburring R)
e ≧ N–5–x 1 max.–a 1 – 3 ＊ a 1 : Step R length
＊ 5: N length tolerance ＊ 3: Tolerance of Step R length
Light deburring is carried out on the corners of the tip to measure the P/W dimensions.
■ Guaranteed Range of Base Material Hardness Rectangular Ejector Pins
P
Deburring of corners
x 2
b 2 Guaranteed Range of Base Material Hardness
T ＋ 2
About processing burring: W hen cutting (with a blade) or grinding (with a grinding stone) steel, small splinter shaped burrs occur on the edge of the processed surface. For example, just like splinters occur when wood is cut with a saw, similar small splinters occur when processing metal. These splinters are called burrs. In general, the size of the burrs is smaller for harder materials. On the other hand, the pieces of material that melts and is caught in gaps during casting, die–casting, and molding of plastics are called flash.
Annealed head
① ②
③
L
In English, the burrs caused in processing are called BURRs, while those cause in molding are called FLASH, or FIN. Reference: Zukai Kikai Yougo Jiten (Illustrated Dictionary of Machinery), THE NIKKAN KOGYO SHIMBUM, LTD.
b 2 ≧ L−x 2 max.
■ Base Material Hardness of Ejector Pins
x 2 max.
M Material
Head thickness (T)
③ ( Guaranteed Range
of base material hardness )
①
②
■ Relationship with Step R and Coaxiality/Head Part of Rectangular Ejector Pins
T4 (4 mm)
30
Step R
SKH51
28–35HRC (reference value)
28–60HRC (reference value)
58–60HRC
JIS (4/6/8 mm)
35
a 2 ± 3
SKD61 equivalent+Nitrided
28–45HRC (reference value) (Excluding nitrided surface)
28–45HRC (reference value) (Excluding nitrided surface)
40–45HRC (Excluding nitrided surface)
P D
JIS (6/8 mm)
40
a 1 ± 3
（ L － N ）
－ 5 0
N
• The head part of SKH51 is annealed to about 30HRC. The head part of SKD61 equivalent + Nitrided is annealed to about 40HRC.
L
■ Guaranteed Ranges of Nitriding and Surface Hardness of SKD61+Nitrided/Rectangular Ejector Pins Rectangular ejector pins for large molds ※ Cross–sectional view M Material Ejector Pin Surface Hardness ①
■ Step R and Concentricity of Rectangular Ejector Pins In order to ensure the effective dimensions of the length (L–N) of the rectangular tip section (P/W), (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 the rectangular tip section (P/W) and shaft diameter (D). Size of step R: approximately R95–105 ＊ (N Short type R65–95) ＊ 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 1 and a 2 ) of step R: a 1 = 5 + D−W 2 × (2R− D−W 2 )
■ Relationship with Step R and Head Part of Rectangular Ejector Pins Head part ( φ H) may contact to grindstone depending on specifications between Step R and P/W, N, φ D or φ H dimensions. (Refer to the right photo) Following formula is solutions to avoid the contact. (In case of P dimensions direction, please calculate by replacing W by P) ＊ This is theoretical value, but not a guaranteed one. Size of step R: approximately R95–105 ＊ (N Short type R70–80) ＊ 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. N ＞ T + 5 + [ H−W 2 × { 2 × (R−0.2)− H−W 2 }
② (Guaranteed range of nitrided surface hardness)
b 3 (Guaranteed range of nitrided surface hardness)
x 3 (x 3 =N)
SKD61 + Nitriding
Base material hardness – 900HV– (without nitrided layer) (with nitrided layer)
900HV–
1
2
N
L
D−P 2
D−P 2
a 2 = 5 +
−0.04 ]
× (2R−
)
• Nitriding
Nitriding is one of the steel surface treatment methods.
(Nitrided)
The steel is placed in a furnace that is then filled with nitrogen gas, and at high temperatures (around 500°C) a hardened layer combined with the nitrogen is formed on the surface of the steel.
*The above formula includes profile tolerance of roughing and finishing. Coaxiality of rectangular tip (P/W) and retention diameter (D): 0.2mm or less
• Nitrided
This refers to the depth of the hardened layer formed on the surface of the steel by nitriding treatment.
Depth
The nitrided depth of MISUMI's plastic mold rectangular ejector pin Hardness of 900HV– is 0.003–0.008 mm (reference value), and the depth at which the hardness of steel increases due to the combination with nitrogen is 0.1 mm from (reference value) than the surface. The nitrided depth of straight ejector sleeve and center pin is controlled by adjusting nitriding temperature and treatment time in accordance with shaft diameter size. In the case of (L-N) part of rectangular ejector pins, nitrided depth is controlled by adjusting nitriding temperature and treatment time in ac- cordance with tip diameter (P) size. For this reason, the surface hardness of the retention diameter (D) is slightly lower at around 500HV (reference value).
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