Drilling aluminum

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

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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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
 
savarin said:
I forgot to mention I also use copious amounts of wd40 when drilling ally.
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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
 
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.
 
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
 
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 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.
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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.
 
savarin said:
I forgot to mention I also use copious amounts of wd40 when drilling ally.
Click to expand...

Should be using Boelube when drilling aluminum or alumitap, They are specific to the most common aluminum alloys. Tim
 
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
 
What about using Parabolic drill bits? Would that help?
 
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