# Drilling aluminum



## prasad (Dec 28, 2014)

I have a question I always wanted to ask but never asked until now. I have always observed that through hole of drilling aluminum  is easy until the drill bit reaches the end of the hole. I always pull the bit out frequently to clear the chips  and it cuts like butter initially.  When it is about to break through  it appears to struggle. When it gets near the end of the hole the bit appears to stall or behaves odd. Why? Is there something I must do differently to get over this behavior? 

Thanks
Prasad 
Wynnewood PA


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## autonoz (Dec 28, 2014)

I have always contributed it to the bit catching on the thin edges of the piece being drilled as it breaks through the end.


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## kd4gij (Dec 28, 2014)

If you ease off and use light pressure it helps.


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## Micke S (Dec 28, 2014)

The end chip binds the drill when the tip starts to project.


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## compsurge (Dec 28, 2014)

Don't hesitate to ask questions. This is an excellent question.

From what I gather, the drill bit flute/spiral tips have sharp points. This sharp point grabs soft sheet material (plastics, brass, copper, aluminum) very easily. I think this video by Tom's Techniques illustrates the point and a simple solution. There are specialized drill bits out there, but I don't see the need to spend more money than you have to when simply smoothing that tip will do it a lot cheaper.


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## Ebel440 (Dec 28, 2014)

I think it's partially due to the metal pushing out of the way rather then cutting. If you stop when your almost through a piece of metal and flip it over you'll see the dimple it makes before breaking through.  It's why drill presses used to be called sensitive drills. It was because you could feel the bottom and slow down feeding when breaking through. It's not just aluminum all metals do it.


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## savarin (Dec 28, 2014)

I tend to use a hard wood as a backing and clamp the ally to that. It seems to help and definitely stops the ally from climbing up the drill as it breaks through.


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## prasad (Dec 28, 2014)

compsurge said:


> Don't hesitate to ask questions. This is an excellent question.
> 
> From what I gather, the drill bit flute/spiral tips have sharp points. This sharp point grabs soft sheet material (plastics, brass, copper, aluminum) very easily. I think this video by Tom's Techniques illustrates the point and a simple solution. There are specialized drill bits out there, but I don't see the need to spend more money than you have to when simply smoothing that tip will do it a lot cheaper.



Hi

Thanks. I saw the video and it asks that the tip of drill bit be blunted. I will try that next. Today I was drilling through a 1 inch thick aluminum piece and I had to drill 8 holes. It irritated me as I had to stop too many times to get clear the tip of drill bit.  The aluminum piece was clamped on top of 123 blocks and securely clamped down. 

Thanks and HNY
Prasad
Wynnewood PA


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## road (Dec 28, 2014)

I used to work on an assembly line as a driller,  ( No Crap really I did )  I had 12 - 1/4" holes to drill on  each door panel.  These were roll-up Semi-trailer doors. So you can imagine.   fast and furious drilling was required with an air drill.
The best perk of the job , we got to keep the  burned Dormer drill bits because they cost too much time to resharpen them.  haaa !  I must have 60 1/4" bits left. 
At home  I've had this happen so much,  I have had clamped items tossed off the table or vise, been nipped by parts and  here and there. after the last sliced finger I have tried to investigate this carefully.
This is what I have concluded.  

What happens is as the bit breaks through the " chip "  or " flashing " that is left just before the final dia. is cut acts like a screw thread on the flutes of the drill bit. coincidentally the larger the bit the more violently it can happen. 

Clamping with sacrificial woods or a type of backer can help to prevent this. 
As well as learning to listen to the bit & "feel the cut as it goes" .

I tend to "peck " with my drill press if I can. depending on the materials and the drill speeds. 
I learned to listen to the cutting of the bit. I Know it sounds different as the bit gets closer the break through point.  

just my point of view...


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## darkzero (Dec 28, 2014)

Ebel440 said:


> I think it's partially due to the metal pushing out of the way rather then cutting. If you stop when your almost through a piece of metal and flip it over you'll see the dimple it makes before breaking through.  It's why drill presses used to be called sensitive drills. It was because you could feel the bottom and slow down feeding when breaking through. It's not just aluminum all metals do it.



That's my thinking also. I notice that it seems to worsen with the larger the drill bit. Not as bad with smaller drills so if you drill through with a smaller bit first, it eliminates the issue when you step up in drill sizes.


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## savarin (Dec 28, 2014)

I forgot to mention I also use copious amounts of wd40 when drilling ally.


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## prasad (Dec 28, 2014)

road said:


> I used to work on an assembly line as a driller,  ( No Crap really I did )  I had 12 - 1/4" holes to drill on  each door panel.  These were roll-up Semi-trailer doors. So you can imagine.   fast and furious drilling was required with an air drill.
> The best perk of the job , we got to keep the  burned Dormer drill bits because they cost too much time to resharpen them.  haaa !  I must have 60 1/4" bits left.
> At home  I've had this happen so much,  I have had clamped items tossed off the table or vise, been nipped by parts and  here and there. after the last sliced finger I have tried to investigate this carefully.
> This is what I have concluded.
> ...



Thank you for sharing your knowledge. I drilled 8 holes today and I stopped each time I felt that the bit was binding. Idid it many times for each hole to clear the ships from the drill bit. I think I have been lucky so far because nothing went wrong. Everything was clamped tight but after reading your post I will remember to be more careful next time. I will start using sacrifical wood support below the pice being drilled.  

Thanks
Prasad


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## prasad (Dec 28, 2014)

savarin said:


> I forgot to mention I also use copious amounts of wd40 when drilling ally.



Yes, I did that too. However when the bit got close to the end it started binding. I had to take it out and clean the flutes before attempting again. 

Thanks
Prasad


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## Fabrickator (Dec 28, 2014)

It really helps to drill a pilot hole for anything bigger than 1/4" too.  Also, deep hole devolp a lot of friction and feel like it's not progressing.


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## silence dogood (Dec 28, 2014)

This is from my observation.  When the drill gets to the thin part of the material, the material is too thin to support the bit.  Hence, instead of cutting, the bit punches through the material.  Wood will splinter.  Plastic or metal will flare out.  Using a clamped sacrificial backing plate makes much smoother though holes.  Cutting lube helps in many cases.  My mill has less run-out than the drill press,  so I use the mill for more critical holes  Last of all,  I've noticed that as one gets near the end of the hole, you can feel it. So go easy.  The video on Tom's techniques was interesting, I'll have to try that.  Mark


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## Tony Wells (Dec 29, 2014)

Another factor I haven't seen mentioned is the possibility of an off-center web/point. This will cause the bit to run out (wobble) and actually cut over its actual size. Usually this can be observed by unequal chips coming off the bit. Then, once the material gets too thin to support the actual point, or breaks through, the wobble more or less disappears and the drill cuts close to size, meaning it can be grabbed in the hole. If this is part of the problem, you should see a slight step where the hole size changes just above the exit. Also check the hole size on the entry and compare it to the exit.


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## brav65 (Dec 29, 2014)

Tony Wells said:


> Another factor I haven't seen mentioned is the possibility of an off-center web/point. This will cause the bit to run out (wobble) and actually cut over its actual size. Usually this can be observed by unequal chips coming off the bit. Then, once the material gets too thin to support the actual point, or breaks through, the wobble more or less disappears and the drill cuts close to size, meaning it can be grabbed in the hole. If this is part of the problem, you should see a slight step where the hole size changes just above the exit. Also check the hole size on the entry and compare it to the exit.




Tony I love your signature quote. It is a shame our society has decided to look down on people who use their hands and minds to create as opposed to being a leach like many of  the "successful" people in our country.


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## astjp2 (Dec 29, 2014)

savarin said:


> I forgot to mention I also use copious amounts of wd40 when drilling ally.



Should be using Boelube when drilling aluminum or alumitap,  They are specific to the most common aluminum alloys.  Tim


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## astjp2 (Dec 29, 2014)

Not one person mentioned that when you drill aluminum, it will get hot as you get close to the end.  Aluminum will change temper/hardness at 250*F for many common alloys.  I am talking 6013-T6, 7078-T8651, 2024-T4 allows really act weird when they get hot.  The 6013 gets gummy and galls, the 7078 has retrogression and re-aging in the temper but will go soft when the temps get elevated causing a chunk to blow out.  A little cooling oil will keep the temps down and chips being made.  Tim


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## EmilioG (Feb 17, 2015)

What about using Parabolic drill bits? Would that help?


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## Wreck™Wreck (Feb 18, 2015)

What about using Parabolic drill bits? Would that help?

No.

This is what happens when using a manual feed drill press, when the tool passes through the far side of the material it will grab the very thin web left and spiral in like an auger. This happens because you have no control over the feed rate, this is the same reason that it is often unwise to climb mill on a manual milling machine.

Try this, if your drill press has a spindle lock engage it slightly so that the handle has drag enough not to advance by itself when passing through the far side. This is what drilling into another piece of material as a base does, it controls the feed rate as if it hasn't passed through the material at all, this only works once however without moving the backing material for each hole. It also does not let the, for lack of a better term "burrs" that are created that spiral up the drill flutes to form, dulling a perfectly good drill is very silly.

Good luck


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