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Drilling deep in delrin

CMacine

Plastic
Joined
Nov 13, 2018
Location
Utah USA
Hello

I have a job coming up that involves drilling a 7/8 inch hole about 9” deep in delrin on a engine lathe. The last company that did this wound up shattering the delrin while drilling and blowing a hole through the ceiling of his shop. He said that the drill grabs the material too aggressively and gets sucked in. I was not able to get any more details on his set up. While drilling some simple parts on a drill press I had it bite so hard it sucked the part and the vice up off the table. I found that using a spade bit for wood from the hardware store worked very well and did not grab the material like a twist drill did.

I want to avoid all of these problems. Can you recommend a drill for this 7/8” hole 9” deep? Do I need to re grind the drill? I can drill from both ends but would prefer doing it in one shot.

Thanks
 
Not sure what the hell that guy was doing but...you can pretty much ram a drill through delrin as fast as you can feed it. Throw some coolant at it and clear the chips here and there. I would say I'm amazed but I'd be lying.
 
Onsrud makes drill bits for plastic I have used them on UHMW they work really good but not 9" deep the flutes only go in about 4" once you pack the bit it is going to stick and pull the part out of the chuck or you will have to peck it to death. I would use the spade bit and a vacuum to suck the chips that works pretty good just break the string every so often.
 
Don't pilot, always drill to size right away. I use regular HSS twist drills. Probably need a long length one for that.
 
my guess would be they were using a mt shank drill that was not seated well. deep holes in delrin are not a problem just don't drill past the flutes that's a recipe for melt. peck drill and some coolant or I like to liberally brush on some Acculube #10 perfect tap along the drill (which is a great general purpose cutting fluid). even some wax lube along the flutes help to keep the heat down. it's important to keep the heat down as the hole will shrink and grab.
 
The last company that did this wound up shattering the delrin while drilling and blowing a hole through the ceiling of his shop.

That sounds like a massive exaggeration or the other guy was drilling UHMW.
I've never had a drill grab in Delrin. That is arguably the best material to machine on the planet.
 
Hello

I have a job coming up that involves drilling a 7/8 inch hole about 9” deep in delrin on a engine lathe. The last company that did this wound up shattering the delrin while drilling and blowing a hole through the ceiling of his shop. He said that the drill grabs the material too aggressively and gets sucked in. I was not able to get any more details on his set up. While drilling some simple parts on a drill press I had it bite so hard it sucked the part and the vice up off the table. I found that using a spade bit for wood from the hardware store worked very well and did not grab the material like a twist drill did.

I want to avoid all of these problems. Can you recommend a drill for this 7/8” hole 9” deep? Do I need to re grind the drill? I can drill from both ends but would prefer doing it in one shot.

Thanks

I kid you not, I'm being 100% serious. I think I've heard that story before, and might have worked for that moron. No names. He means well with his warnings, and has decent foresight for potential problems. But he always needs some catastrophic story to back him up, instead of just saying it. Solution has already been stated. To reiterate; coolant, no pilot, don't baby it.

R
 
Lets see... I use a lot o "LoL and LMAO", but this has to be the first time in along time it was really true... (:


blowing a hole through the ceiling of his shop.

:popcorn:

edit: was it the little piggy's shop made of straw?

I'll huff and puff and bllloooowwwww the house down! hahahha
 
If you're worried about the drill grabbing, brass the drill. Delrin won't care.

I would not be adverse to drilling it half and half undersized and hitting it with a boring bar to pretty it up.
 
That is arguably the best material to machine on the planet.

Arguably?? Its a fact!!! All machined parts should be made from Delrin (or at least all
the machined parts I have to make)..


I've never had a drill grab in Delrin either. Its really mild mannered.. Its hard enough that
you can hold it, its soft enough to cut easy, but hard enough that its not gummy like Teflon or
UHMW :ack2:. I've personally never experienced the grabbing and pulling with delrin that some
of the other softer plastics are famous for.

I was trying to open up a 5/16 hole to 3/8 the other day in Nylon, with a hand drill..
Damn drill just screwed itself into the nylon.. Like a self tapping drill/screw?
Delrin would never do that, its too well mannered.
 
Lets see... I use a lot o "LoL and LMAO", but this has to be the first time in along time it was really true... (:


blowing a hole through the ceiling of his shop.

:popcorn:

edit: was it the little piggy's shop made of straw?

I'll huff and puff and bllloooowwwww the house down! hahahha

Aside from just thinking about the process and facts--a part that is 9" long in a manual lathe chuck, with a 7/8" Drill inside of it, suddenly pulled out of the chuck, somehow escaped having a big ass Drill in it----THEN managed to fly upward with enough force to break a hole in the roof!!!!! Good God, WTF is going on?

Meanwhile, back in reality-assuming the Drill did bite too deep, the part spun in the chuck. What else could realistically happen? The MT slipped maybe, but the fucking thing didn't drill itself a hole deep enough to let the whole Drill go.

Even if the part somehow got away, if it had that much force it would break. Delrin isn't great for hard impact.
 
Where I come from (research machine shops established by post-war European emigres where lightly used tools can hang around for a REALLY long time) they'd always have two sets of HSS drills, one for aluminum and steel with the normal cutting angle and one for brass and plastic with the cutting angle ground back to 90 degrees or so. I started a thread recently about the history of Delrin in prototyping because in physics anyway, Nylon and teflon were preferred for vacuum outgassing reasons so I'm not sure what the official old European guy view on Delrin is. So I would ask, would it still be better to use less acute cutting angle on Delrin if you happened to have such a drill, or is Delrin so good it really doesn't matter?
 
If grabbing its an issue, just flatten the lips of the drill slightly and it won't dig in or grab. if you are getting a formaldehyde smell during machining, you are melting the resin- slow things down a bit and life will be good.
 
Call me crazy Dan. I've heard it before about the smell of formaldehyde, in relation to melting Delrin/Acetal. I have no idea what formaldehyde smells like! I don't hang out in the same places some as you guys, I guess. I'm trying to grasp why or under what circumstances, you people are smelling embalming fluid. :)

R

"This Chloraphorm smells funny to me, here you smell it and see if you think it smells weird too"
 
Call me crazy Dan. I've heard it before about the smell of formaldehyde, in relation to melting Delrin/Acetal. I have no idea what formaldehyde smells like! I don't hang out in the same places some as you guys, I guess. I'm trying to grasp why or under what circumstances, you people are smelling embalming fluid. :)

R

"This Chloraphorm smells funny to me, here you smell it and see if you think it smells weird too"


I've smelled the formaldehyde (You never dissected anything in school, Rob? We dissected cats for my AP Biology class my freshman year... They hung around for about 2 weeks before we finished... Yeah, I'll never forget what formaldehyde smells like...)... I also think it vaguely smells like the Crayola brand paints we used in art class when I was in elementary school.... Not sure why... Smell is a funny thing, it's really good at triggering long dormant memories...
 
Hello

I have a job coming up that involves drilling a 7/8 inch hole about 9” deep in delrin on a engine lathe. The last company that did this wound up shattering the delrin while drilling and blowing a hole through the ceiling of his shop. He said that the drill grabs the material too aggressively and gets sucked in. I was not able to get any more details on his set up. While drilling some simple parts on a drill press I had it bite so hard it sucked the part and the vice up off the table. I found that using a spade bit for wood from the hardware store worked very well and did not grab the material like a twist drill did.

I want to avoid all of these problems. Can you recommend a drill for this 7/8” hole 9” deep? Do I need to re grind the drill? I can drill from both ends but would prefer doing it in one shot.

Thanks


Just in case of grabbing in a quill app, just keep some tension of the quill brake.

This is the "CNC" board tho.



--------------------

Think Snow Eh!
Ox
 
I should add it can grab when it punches through the other side if feeding heavy, mostly with bigger drills. Moderate feed is usually good, too heavy can fracture it a little. PVC does that too.
 








 
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