Ejector pin holes

Motorsports-X · Jul 21, 2017

Just curious. Is there any current tools on the market that allow you to drill an ejector pin hole to size without any reaming (therefore saving a setup, and extra operation.) I have used some guhring carbide drills that have 0 discernible out of round condition when measured with standard tools, so i'm wondering if anyone is using them directly for core/ejector pins in tools.

Thanks

TDegenhart · Jul 21, 2017

What do you mean by standard tools? If there is a fit problem of the ejector pin in the hole, the plastic will find it. The only solution then is to grind the hole and use an oversize ejector pin. Costly.

Tom

Greg White · Jul 21, 2017

always reamed the last 1" or 2,depending on the dia. no extra setup, your there wit da drill anyway.

gun drill could/would hold size,if where it broke into part was flat enough.

never seen ground ej pin holes, not in automotive anyway,plastic takes more than a .001 to flash,no?

usta do non crucial ej on radial drill.
build molds mosta my working days.
all ears here to hear wat the other men say.
Gw

Davis In SC · Jul 21, 2017

Many of my mold cavities are small enough to lift and carry. Most are hardened. I generally drill and ream them .002 under, then hone to fit the pins after hardening. Some of my cavities make thin nylon parts... The nylon will flash and cause rejects if the pin clearance exceeds .0002 (two tenths). I hone and lap a lot of holes to keep molds running. Royal will grind pins to any size you order, I buy lots of them in half thou increments to allow oversizing holes. For small ejector pins under 1/4 inch, Royal Brand is the best!

Modelman · Jul 21, 2017

Greg White said:
never seen ground ej pin holes, not in automotive anyway,plastic takes more than a .001 to flash,no?

Depends on material and molding pressure. Acetal will flash into .0005, given enough pressure; I'm told Nylon into considerably less.

I do a lot of small intricate parts in HIPS or Acetal. Modern ejector pins are -.0005/-.0008", at least in the small sizes I use. I tend to ream .0005" under nominal size, and lap to size if needed after heat treat.

Yes, I have occasionally used Ghuring metric drills to hit the size I want and lap from there, and it has worked, except when it doesn't, and at that point it means wire EDM'ing the holes bigger, and substituting different pins. A lot of f*ckin' around for little savings in time.

Dennis

Greg White · Jul 21, 2017

i thought you men that can pickup your molds mite say that, automotive, ejs are always on the hidem side(cores)
We had to make it work, hard to put a facia tool on a grinder, if the ejs leaked ,weld up up, run a reamer back thru, little benching, good to G00.
Again never seen ejs ground in Detroit molds, never worked on smaller parts. I think general car parts, door panels, dashs and the like dont use easy leaking material?
Sorry for running off subject, sorry.
Gw

Davis In SC · Jul 21, 2017

Greg White said:
i thought you men that can pickup your molds mite say that, automotive, ejs are always on the hidem side(cores)
We had to make it work, hard to put a facia tool on a grinder, if the ejs leaked ,weld up up, run a reamer back thru, little benching, good to G00.
Again never seen ejs ground in Detroit molds, never worked on smaller parts. I think general car parts, door panels, dashs and the like dont use easy leaking material?
Sorry for running off subject, sorry.
Gw

Yes, some of the cheaper models use Polypropylene, which is fairly easy to flash, but many auto components are made of a Polycarbonate/ABS alloy which is harder to flash.. And as stated the back side of many parts are hidden, so some flash is allowable.

macds · Jul 21, 2017

I prefer punching a start hole, and wire cutting my ej pin holes.
I get better fits, and the white layer provides and nice hard coat for the pins to run on.
Dont have to worry about bellmouthing the bloody hole either.
I rather take the time and build the prick to last, as opposed to a cheap turd thats going to gass out and flash

Davis In SC · Jul 21, 2017

macds said:
I prefer punching a start hole, and wire cutting my ej pin holes.
I get better fits, and the white layer provides and nice hard coat for the pins to run on.
Dont have to worry about bellmouthing the bloody hole either.
I rather take the time and build the prick to last, as opposed to a cheap turd thats going to gass out and flash

I still service some molds that I built 20+ years ago.. 32 cavity, discrete cavities in a fully hardened base.. These molds run millions of parts per month with only minor repairs and upkeep.

macds · Jul 21, 2017

Davis, if you have a proper honing machine, and know how to use it, its an absolute weapon.
Trouble now days is finding anyone with the patience and skills to feel what the hone is doing.

I remember fitting pins during my apprenticeship using grooved nitrided pins and 1000 diamond compound for medical tools. By hand.
Ironically, we used cigarette ash \ talc to polish turbuhaler cores and cavities.
Went nicely with a cold rye at the outdoor company picnic table on a nice summer day.

I miss the old days of status quo, where a good toolmaker had a long leash, a short temper, a Gauloises, and a rye

Good times!

5 axis Fidia guy · Jul 22, 2017

We have done it with success with Mitsubishi drills. It can be hit or miss, if it works you will save a ton of time, until that one hole that drills oversize, then you go oversize pin, then there is one oddball in the mold, which in the long run what did you save?. We normally just wire all our holes overnite, done. I would never even consider it on molding nylon.

NaRbO · Jul 22, 2017

We have drilled ejector pin and core pin holes at our shop. Mainly in H13 50Rc. Have tried OSG, Guhring and Titex drills. Titex is the most consistent, drills pretty much right on size to where an ejector pin will enter but not a core pin (core pin is about .001" larger). It will still leave a bit of a bell mouth on the hole, so we have to drill first and then semi and finish the insert to get rid of it. We have had pretty good success with 5x and 8xD drills from Titex. I still prefer wire cut as it is the most consistent and accurate.

On hard steel I find as the drill wears it will drill under size, then we lap to fit.

Machinist1989 · Apr 20, 2018

We used to drill anything from around 1/8"-5/8" with Sumitomo carbide drills for ejector pins and most would come out like glass. To keep the longer drills from "whipping" and if you have CTSI they like a pilot hole so that you can feed into the hole at a low rpm before increasing to the full RPM.

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