Drilling Small holes in Aluminum (1/32)- what we learned
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    Default Drilling Small holes in Aluminum (1/32)- what we learned

    I have often come to this sight for info. But there did not seem to be a lot here or on the web about drilling small holes, and small holes in aluminum in particular, when searching for information to help with a job we had.

    So the job was drilling (3) 3/8 6061 aluminum plates to be used for a vacuum tool on a can depalletizer. Each plate was about 48" square and had around 2800 holes. The holes were drilled 9/32 (.281) .300 deep then drilled 1/32 the rest of the way through. The machine we were using was a Laguna CNC router. For tooling we used a 9/32 stub length carbide drill and a 1/32 HSS drill with bright finish and a fast spiral. From what I could gather the HSS with bright finish was better than coated.

    To start with we used a standard spray mist coolant mixed strong. On the carbide drill, we ran about 10k rpm with a feed of .002 per tooth. There was not enough power and we stalled the drill in the fourth hole. But since there was lots of room cutting speed wise, we increased out rpm to 13k but kept the inches per min the same. This seemed to work fine. On the 1/32 drill we ran 20k rpm with a feed of .0005 per tooth. We cut about 100 holes before the first drill broke. The second drill only lasted about 30 holes. After pondering the problem we decided to switch from mist coolant to WD40. Seemed to solve the problem as we drilled the rest of the holes with the third drill. We the put that third drill and a drill we had used to drill 20 test holes under a microscope. That picture is included. It is not the clearest picture (we need to 3D print a camera to microscope adapter) but you can see a bit of dulling on the left hand drill (the one that drilled 2600 holes) but the flutes are clean and there is no build up. The one on the right has build up on the cutting edge and around the outside plus a chip stuck in the flute. img_4251.jpg

    As a side note with the breaking the drills we ended up with around 10 holes that were not drilled (We did not drill them with the CNC as there was still broken drills stuck in 2 holes and the Laguna cnc control does not let you start in the middle of the program. Yes we could have written a small program to dill those few holes but it did not seem worth the effort). So we mounted a 1/32 drill in a right angle die grinder and drilled them with that. Seemed to work fine.

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    One thing I advise with small drills is to look at each drill with a loop.
    That simple inspection takes only a minute so is well worth the time. look for point at center, clearance at the point and being sharp.

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    I had a job once drilling and tapping a 1/4-20 holes in a 1/2" thick aluminum plate. The plate was four feet by eight feet and there was a tapped hole every inch on the entire plate. I got bored watching it cut and walked away for 4-5 minutes and in the brief time I was away the coolant ran out, and the tap ran dry, broke, and ground it's way into several holes destroying the entire piece.

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    Not drilling related, but this makes me think of 25 years ago...a major chemical plant here had some sort of process where gas was passed through a membrane....this was a sheet of .090" thick anodized aluminum with thousands of very small, precision holes. It was a big sheet, like 60" x80". Over time, the holes would become eroded enough that the sheet would need to be replaced. So they had two future-use sheets in the warehouse, carefully wrapped and on a pallet. $80,000 each.

    Inventory time came, and one of the workers was told to toss anything that was surplus in the scrap bin. He peeked inside the wrapper, saw a couple sheets of plain aluminum, and thought it was stupid they were taking up valuable shelf space...so he tossed them.

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    OP - Excellent post.

    These come up every now and then.
    Very Large numbers of holes for a particular use.

    And the cost to make such a part is typically astronomical.
    Mostly because of the broken drill bits effect and total machine time and work hours required can be very very high.

    Especially if the holes are deep in D and or the material is expensive, like large alu or SS or exotics.
    Or if very precise holes are needed.

    ? Can you drill them in one go, if one broken drill ruins the workpiece and you need to start over ?

    It´s non-trivial especially where the machine time may be 100 hours plus.
    And You perhaps cannot fix a workpiece, maybe, and need to make a new one.

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    Default Drilling 1/32 dia. holes in 6061 Al.

    Quote Originally Posted by DZ&F View Post
    I have often come to this sight for info. But there did not seem to be a lot here or on the web about drilling small holes, and small holes in aluminum in particular, when searching for information to help with a job we had.

    So the job was drilling (3) 3/8 6061 aluminum plates to be used for a vacuum tool on a can depalletizer. Each plate was about 48" square and had around 2800 holes. The holes were drilled 9/32 (.281) .300 deep then drilled 1/32 the rest of the way through. The machine we were using was a Laguna CNC router. For tooling we used a 9/32 stub length carbide drill and a 1/32 HSS drill with bright finish and a fast spiral. From what I could gather the HSS with bright finish was better than coated.

    To start with we used a standard spray mist coolant mixed strong. On the carbide drill, we ran about 10k rpm with a feed of .002 per tooth. There was not enough power and we stalled the drill in the fourth hole. But since there was lots of room cutting speed wise, we increased out rpm to 13k but kept the inches per min the same. This seemed to work fine. On the 1/32 drill we ran 20k rpm with a feed of .0005 per tooth. We cut about 100 holes before the first drill broke. The second drill only lasted about 30 holes. After pondering the problem we decided to switch from mist coolant to WD40. Seemed to solve the problem as we drilled the rest of the holes with the third drill. We the put that third drill and a drill we had used to drill 20 test holes under a microscope. That picture is included. It is not the clearest picture (we need to 3D print a camera to microscope adapter) but you can see a bit of dulling on the left hand drill (the one that drilled 2600 holes) but the flutes are clean and there is no build up. The one on the right has build up on the cutting edge and around the outside plus a chip stuck in the flute. img_4251.jpg

    As a side note with the breaking the drills we ended up with around 10 holes that were not drilled (We did not drill them with the CNC as there was still broken drills stuck in 2 holes and the Laguna cnc control does not let you start in the middle of the program. Yes we could have written a small program to dill those few holes but it did not seem worth the effort). So we mounted a 1/32 drill in a right angle die grinder and drilled them with that. Seemed to work fine.
    Try Kerosene for a cutting fluid. 6061T6 is used for extrusions and is very mealy. It will stick to the cutting edge and fill the drill flutes. "5052H34 could have been a better choice of material for machining".

    Roger

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    Toss anything that is surplus.

    You just gotta love the bean counters! I bet they stayed and that worker was toast!



    Quote Originally Posted by GregSY View Post
    Not drilling related, but this makes me think of 25 years ago...a major chemical plant here had some sort of process where gas was passed through a membrane....this was a sheet of .090" thick anodized aluminum with thousands of very small, precision holes. It was a big sheet, like 60" x80". Over time, the holes would become eroded enough that the sheet would need to be replaced. So they had two future-use sheets in the warehouse, carefully wrapped and on a pallet. $80,000 each.

    Inventory time came, and one of the workers was told to toss anything that was surplus in the scrap bin. He peeked inside the wrapper, saw a couple sheets of plain aluminum, and thought it was stupid they were taking up valuable shelf space...so he tossed them.

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    To the OP -- great write-up! I have been meaning to get a set of small pivot drills such as these: Flat Pivot Drill Sets

    For jobs like that. Pivot drills require more pecking since the don't have flutes. But the drills are a lot stronger than the usual twist drill. Stronger because there is no thin web. Commonly used by clockmakers.

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    Thanks for the excellent write up.I am very surprised that you didn't have problems with chips landing in your "pilot" hole and breaking your small drill. Edwin Dirnbeck

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    Quote Originally Posted by edwin dirnbeck View Post
    Thanks for the excellent write up.I am very surprised that you didn't have problems with chips landing in your "pilot" hole and breaking your small drill. Edwin Dirnbeck
    Between drilling the pilot holes and small holes we vacuumed and blew off all the chips or I am sure it would have been an issue. As for the drill chips from the small holes the were fairly long and really light and did not seem to end up in the holes.


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