Carbide Drilling for EJ Pins

novotny731 · Nov 14, 2019

Hey,

I'm on any tips or tricks on carbide drilling. I'm using through coolant. I am trying to use the carbide drill for ejector pins on plastic injection molds. The problem I'm having is the hole is just a little bit too small for my ejector pin. I haven't done much carbide drilling. We have all these carbide drills here. I'm trying to put them to use and save time. Any ideas would be great! Thanks for your time!

Peter Neill · Nov 14, 2019

Seriously?
Use a reamer, drilling is a roughing operation and no where near close enough for an ejector pin hole. Many plastics will flash on 0.001" or less and you need it as close as possible.
Depending on pin length you may want to relieve it as well. In which case, drill, flip over, relieve, and then ream.

DavidScott · Nov 14, 2019

What Peter said. I forget the formula but I think you want about 3 diameters reamed then about .005" clearance for the rest of the hole. The tighter clearance helps hold the grease. Also, make sure your reamers are reaming the size of hole you expect, ej holes have pretty tight tolerances.

litlerob1 · Nov 14, 2019

I'm not a mold guy. But I am a hole making guy. I NEVER use Reamers, I hate Reamers. I drill to size, I can hold .0005" with a Drill. Surface finish isn't as good as a Reamer (theoretically), but Straighness, Roundness and Size are fine. I would recommend a tool, but don't know the material you are working with or the Spindle turning the tool.

R

novotny731 · Nov 14, 2019

Seriously? Yea, I am serious. I know how to ream and do it the old way, just trying to try new things. See if I can speed up the process. If I can't get it to be consistent and accurate, then I'll go back. You're making it sound bad to try new things. Yeah, I know how to make EJ Pin Holes. litlerob1 Makino 14,000 RPM Spindle I'm cutting P-20 5/32 DIA. and 3/16 DIA.

lumley32 · Nov 14, 2019

I used to do a job that couldn't be reamed, we used carbide drills with a DLC, we had to hit 6.35mm -0mm +0.025mm. there were no real tricks to it TBH, drill the hole (in sample material) with an off the shelf drill, measure the hole, get the drills ground the difference, recoat then go to town!

don't get me wrong if the coating wears then you're out of tolerance, but in some cases, it was worth it!

litlerob1 · Nov 14, 2019

novotny731 said:
Seriously? Yea, I am serious. I know how to ream and do it the old way, just trying to try new things. See if I can speed up the process. If I can't get it to be consistent and accurate, then I'll go back. You're making it sound bad to try new things. Yeah, I know how to make EJ Pin Holes. litlerob1 Makino 14,000 RPM Spindle I'm cutting P-20 5/32 DIA. and 3/16 DIA.

My first call for ANY and ALL drilling operations is Gurhing. Particularly a job that isn't exactly standard. Good knowledgeable customer help.

g-coder05 · Nov 14, 2019

I get the part where you want to speed up a process but in your application do you really think that's a good decision? You admittedly are not familiar with carbide drills but since your shop has many of them you want to learn how they work. Great, perhaps play with them on something besides a tool. I'm not sure about the complexities of your tools but typically they are not just a quick job. Some of ours take weeks or months to complete and if I find out somebody has to make a repair because he/she wanted to cut corners it's gonna be a bad day.

Mike1974 · Nov 14, 2019

So drilling ejector holes for the actual mold core/cavity, or the ejector plate itself? In ejector plate, just step up your drill size a thou or so if you want to "one and done" it. If for a cavity, we used to jig grind ours, I think, depending on material being molded. I think glass filled nylon will flash at around .0005" and polypropylene is .001". SO I think it would depend on what you are molding. Hell I wouldn't trust a reamer to hold .0005" for very long so...

indianamoon · Nov 14, 2019

Used to do that all the time and then hone or lap the holes to size

5 axis Fidia guy · Nov 15, 2019

We do it all the time, we use only Mitsubishi drills, they will hold the size, no center drill, straight thru with high pressure coolant. It's actually quite unbelievable that it works, AND you get a much smoother hole compared to reaming.

triumph406 · Nov 15, 2019

novotny731 said:
Seriously? Yea, I am serious. I know how to ream and do it the old way, just trying to try new things. See if I can speed up the process. If I can't get it to be consistent and accurate, then I'll go back. You're making it sound bad to try new things. Yeah, I know how to make EJ Pin Holes. litlerob1 Makino 14,000 RPM Spindle I'm cutting P-20 5/32 DIA. and 3/16 DIA.

If that was the case you wouldn't be asking questions here.

TeachMePlease · Nov 15, 2019

triumph406 said:
If that was the case you wouldn't be asking questions here.

To be fair, he said he knows how to make holes, not how to make GOOD holes.

DMF_TomB · Nov 15, 2019

novotny731 said:
Hey,

I'm on any tips or tricks on carbide drilling. I'm using through coolant. I am trying to use the carbide drill for ejector pins on plastic injection molds. The problem I'm having is the hole is just a little bit too small for my ejector pin. I haven't done much carbide drilling. We have all these carbide drills here. I'm trying to put them to use and save time. Any ideas would be great! Thanks for your time!

.
length to dia ratio of drill is the most important thing. you can have somebody drill a million shallow holes per days no problems and then drill deep holes and start having massive broken drill problems and high part scrap loss.
.
just saying trying to save 10 minutes drilling time and then spending 10 hours dealing with broken drill bits most likely you are creating extra time loss not saving any time by the end of the year.

dodgin · Nov 15, 2019

5 axis Fidia guy said:
We do it all the time, we use only Mitsubishi drills, they will hold the size, no center drill, straight thru with high pressure coolant. It's actually quite unbelievable that it works, AND you get a much smoother hole compared to reaming.

People swear by Guhring, but I'd puts Mits solid carbs right up there with the best of them. The MHS line is specifically designed for drilling ejector pin holes in one shot. They're all double margin whereas I think most "universal" solid carbide drills don't get into double margin until 5 or even 8xD.

Nerdlinger · Nov 15, 2019

dodgin said:
They're all double margin whereas I think most "universal" solid carbide drills don't get into double margin until 5 or even 8xD.

Speaking of double margin, I recently had to cross drill a 1” hole in 3” round annealed 4340. We’re using an Iscar SumoCham insert drill. This time around the drill tips were back ordered so we got an alternative that was in stock...it was the same everything but double margin. The hole was pretty wonky and the surface finish was real bad with big swirls in it. Long story short we got the single margin inserts in and everything was back to being perfect. Any idea why the double-margin was behaving so badly? I always thought double margin just drilled straighter, rounder holes with essentially no trade off.

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Carbide Drilling for EJ Pins

novotny731

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Peter Neill

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DavidScott

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litlerob1

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novotny731

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lumley32

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litlerob1

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g-coder05

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Mike1974

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indianamoon

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5 axis Fidia guy

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triumph406

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TeachMePlease

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DMF_TomB

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dodgin

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Nerdlinger

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