eject pin dia for die cas mold

[HEAVY METAL]

my part is callin out .314 dia for an eject pin i assume the pin size is 5/16 hole close to size do i need to hold it. it is a deep hole that i was just going to try to drill/ream

thanks heavy

[Guest]

sounds like they want to make sure the pin won't

seize up to me.

[jagg2499]

Are you sure that the pin size is not a 8mm pin?

[HEAVY METAL]

they want a .314 dia thru hole i'm guessing clearance for .3125 pin. i was thinking of step drilling to size and taking a .3155 dia reamer thru to clean it up . about a 4 inch deep hole. just wondering how much clearance was acceptable for eject pins

[jagg2499]

It depends what plat it is in, if the hole is in the ejecter plate or a support plate then clearance is fine but if the hole is reamed in an A or B plate then you want the pin to fit nice and tight that is why i suggested possible being a 8mm pin cause it is .3149 and normally pin are .0002 to .0005 undersize so that would give you a nice fit

[moldy]

Ejector pins come .0005 to .001 under nominal size depending upon the supplier.

It seems to me the a .314 hole would flash .0025.

In a short period of time this pin will seize as diecast metals tends to flash easy because of the high ejection pressure.

Maybe a 8mm pin will be correct. Better call the molder to clarify this as it could lead to using over-sized pins to correct the sloppy fit. As it is already hardened s-7 or h-13 you will have to wire edm the holes +.005. And the nitemare begins.....

 

Hope this saves you $$$$ and stress!!

Moldy

[moldy]

lines 5+6 should read....

diecast metals tend to flash because of high injection pressures.

Moldy

[Keith @ Solid Code Solutions]

jagg2499

 

0.315 definatley sounds as if it is 8mm nominal, itis either that or 5/16 with way too much clearence that could be be intended as a half cocked vent. 8mm sounds like the one wins the prize to me.

[HEAVY METAL]

thanks looks like best bet is to call customer

[Müřlıń®]

Back when I was building Diecast molds we would always make the EX holes with .005 clearance.

 

We had a Honeing machine for lapping out the holes out to size if we didn't have a reamer.

 

Alu is shot in around 1400 degrees and the ex pins will swell up some.

 

Plus as someone stated it would also vent.

[Kevangel]

4 inches deep?, I would if possibal ream from the back side of cavity block, less chance of bell mouthing at cavity area and I would only have 3.5 times the dia. of actual bearing dia. on the pin and relieve cavity block .015. you can ream small and lap out with a barrel lap in drill press or with hand drill just do it from the bottom, it would be better. they might be venting on that pin. Been a while but aren't die cast dies vented around .006 inches??? not like plastic molds vents of .0005 to .001 (lap after heat treat)

[Müřlıń®]

Also. ex pins with 4" of bearing would be relief drilled from the back to where they only have about a 1" land...that goes for plastic or die cast...

 

Depends on the material Kev, pure nylon flashes around .0005 and ABS flashes around .003....

 

I forget how much polyproplene and polystyrene are, somewhere in between I think.

 

It's been 25 years since I built molds....lol...

[flippinjig]

Heavy,

5/16 ejector pin measures .312 so I drill and ream .313 before heat treat. 3/4" of bearing surface is common, with the rest of the hole relief drilled 1/32 over. I have seen it before but it is rare that customer wants .002 over pin size. Aluminum flashes at .003. I agree with Kevangle, 4" not too deep. I would go from BS also.

 

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