Drilling aluminum

[prasad]

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

 

[autonoz]

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

 

[kd4gij]

If you ease off and use light pressure it helps.

 

[Micke S]

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

 

[compsurge]

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.

 

[Ebel440]

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.

 

[savarin]

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.

 

[prasad]

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

 

[road]

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...

 

[darkzero]

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.