Help Drilling Deep Holes in Aluminum

jmansfield · Mar 30, 2017

I need to drill/ream deep holes in 6061 Aluminum. Hole needs to be 10mm diameter (+/-.1mm), 6in deep, thru hole. I have a manual mill and a drill press available. What is the best way to go about this? Was planning on spot drilling, pilot drilling, then drilling with a letter W drill (.386"), to leave ~0.008" for the reamer. Repeat drill steps on opp side, meet the holes in the middle of piece (thru hole). Then take .394" reamer on the drill press to finish hole.

Suggestions? Am I on right track?

Is drilling from both sides of the piece bad idea?
Should I ream from both sides of the piece as well?
How deep should I peck with the drill?

cmccull166 · Mar 30, 2017

jmansfield said:
I need to drill/ream deep holes in 6061 Aluminum. Hole needs to be 10mm diameter (+/-.1mm), 6in deep, thru hole. I have a manual mill and a drill press available. What is the best way to go about this? Was planning on spot drilling, pilot drilling, then drilling with a letter W drill (.386"), to leave ~0.008" for the reamer. Repeat drill steps on opp side, meet the holes in the middle of piece (thru hole). Then take .394" reamer on the drill press to finish hole.

Suggestions? Am I on right track?

Is drilling from both sides of the piece bad idea?
Should I ream from both sides of the piece as well?
How deep should I peck with the drill? reamer?

Go to Guhring drill website. Parabolic long drill... if possible I would go one size smaller that your mean dia.
But my experiance is they drill on size so it could come out under size if its under your hole tolerance ...
They advertise first peck 10 x dia so almost 4.00 if you want to try that..I know I have been doing this on a CNC with no problems..on a manuel you have feel so whatever...get one long enough you can do it from one side ..no way will you meet in the middle

cmccull166 · Mar 30, 2017

cont..Less peck on all after the initial peck maybe 1/2 inch LOTS of coolant A spray bottle that will stream not mist..It should take way longer to setup than to drill this... maybe 2 minutes.
Oh and I would cdrill and drill 1/4 inch 1 1/2 deep to start a straight hole

cmccull166 · Mar 30, 2017

you do know about thermal expansion.. drills grabbing and all the other bad stuff that happens on a seemingly easy manual process??

AND!!!
You are going to drill this in a rigid vise setup ...clamped to survive the Armageddon...if you try to hold this in place even a bridgeport will rip your arm off..

UMM... the fact you had to ask this question makes me WORRY.

jmansfield · Mar 30, 2017

cmccull166 said:
you do know about thermal expansion.. drills grabbing and all the other bad stuff that happens on a seemingly easy manual process??

AND!!!
You are going to drill this in a rigid vise setup ...clamped to survive the Armageddon...if you try to hold this in place even a bridgeport will rip your arm off..

UMM... the fact you had to ask this question makes me WORRY.

which question

Anybody else got any input?

plastikdreams · Mar 30, 2017

jmansfield said:
which question

Anybody else got any input?

All of them...

jmansfield · Mar 30, 2017

plastikdreams said:
All of them...

oh? no kiddin.

machining isn't my job, my craft, nor my hobbie. I got tasked to do it. I'm seeking advice. Clearly you have none and have nothing better to do with your life than sit here and put people down.

Terry Keeley · Mar 30, 2017

I guess the question is how straight does it havta be? If you drill from both sides and it doesn't meet exactly in the middle is that a problem? If so you'd havta drill it straight through I'd think.

Spot, if it needs to be straight start with a solid carbide "W" stub drill, then a 135* split point aircraft extension drill. Dormer (PTD) have some in HSS, didn't see that size in CO but that would be better. Use a collet in the mill and only extend the drill an inch or so at a time to maintain maximum rigidity. I tried some fancy parabolic flute drills but they were't rigid enough and kept wandering. Peck away, then ream to final size.

I just did some 60D holes in Ti straight to within 0.010" this way, you only have 15D in 6061 so it'll be a piece of cake!

jmansfield · Mar 30, 2017

Terry Keeley said:
I guess the question is how straight does it havta be? If you drill from both sides and it doesn't meet exactly in the middle is that a problem? If so you'd havta drill it straight through.

Spot, if it needs to be straight start with a solid carbide "W" stub drill, then a 135* split point aircraft extension drill. Dormer (PTD) have some in HSS. Use a collet in the mill and only extend the drill an inch or so at a time to maintain maximum rigidity. Peck away, then ream to final size.

I just did some 60D holes in Ti straight to within 0.010" this way, you only have 15D in 6061 so it'll be a piece of cake!

thanks...
no spec on straightness, but yea it's gotta be "reasonably" straight. Sticking a shaft 9.9mm shaft down the hole.

guest · Mar 30, 2017

As said, work your way up on the drill. Stubby, jobber, taper length should get you there. Don't let the chips pack up when you get deep, just take your time and clear the chips.

Ream from the same side in the same setup, stop the spindle at the bottom of the hole so you don't backdrag coming back up.

jmansfield · Mar 30, 2017

guest said:
As said, work your way up on the drill. Stubby, jobber, taper length should get you there. Don't let the chips pack up when you get deep, just take your time and clear the chips.

Ream from the same side in the same setup, stop the spindle at the bottom of the hole so you don't backdrag coming back up.

cool. thank you for answering my questions.

Mtndew · Mar 30, 2017

cmccull166 said:
you do know about thermal expansion.. drills grabbing and all the other bad stuff that happens on a seemingly easy manual process??

AND!!!
You are going to drill this in a rigid vise setup ...clamped to survive the Armageddon...if you try to hold this in place even a bridgeport will rip your arm off..

UMM... the fact you had to ask this question makes me WORRY.

So you exited the womb knowing all of these things and never had to learn them? This guy is asking and wants to learn. Relax brah.

Mtndew · Mar 30, 2017

jmansfield said:
I need to drill/ream deep holes in 6061 Aluminum. Hole needs to be 10mm diameter (+/-.1mm), 6in deep, thru hole. I have a manual mill and a drill press available. What is the best way to go about this? Was planning on spot drilling, pilot drilling, then drilling with a letter W drill (.386"), to leave ~0.008" for the reamer. Repeat drill steps on opp side, meet the holes in the middle of piece (thru hole). Then take .394" reamer on the drill press to finish hole.

Suggestions? Am I on right track?

Is drilling from both sides of the piece bad idea?
Should I ream from both sides of the piece as well?
How deep should I peck with the drill?

Is drilling from both sides of the piece bad idea? No, it's not a bad idea for that length of thru hole if hole location is important.

Should I ream from both sides of the piece as well? I would ream from 1 side if you can to maintain a consistent hole location.

How deep should I peck with the drill? This depends on a few factors, drill type, lubrication, etc. And on a manual mill it's just something that is learned by feel and experience really. Start off with about 1/4" pecks if you can, but generally when you get deeper inside the hole you might have to use smaller pecks.

tay2daizzo8 · Mar 30, 2017

cmccull166 said:
you do know about thermal expansion.. drills grabbing and all the other bad stuff that happens on a seemingly easy manual process??

AND!!!
You are going to drill this in a rigid vise setup ...clamped to survive the Armageddon...if you try to hold this in place even a bridgeport will rip your arm off..

UMM... the fact you had to ask this question makes me WORRY.

Really? its only aluminum and a 10mm drill. Armageddon is a lil much...only need to hold it steady..regular vice mounted on table works just fine... the fact that you answer with this makes me worry

To OP.. you should have no problem going from both sides and reaming from both.. if you go both sides you wont need to buy an aircraft drill.

I know the BP only has 5" of travel but avoid the drill press.
set a hard stop and ream from both sides done deal
stop spindle and rechuck reamer

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