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krems
11-06-2007, 09:05 PM
I've been playing around w/ aluminum lately trying to figure out the best way to drill a precision hole on a milling machine through 2 pieces (.75" ea. or 1.5" inches total thickness) of 2024 aluminum. Is there a proper way to dry machine aluminum. It seems that I get most of the way through and need to pull out to get rid of the chips. Id like to be able to drill to total depth w/ out pulling out of the hole. Is this posible when dry machining...What kind of RPM should I be drilling at...(1/4" - 9/32" hole size).....What about the feed rate. When the RPM was at 2000 the 2 flute bit packed w/ chips. Should I be looking at a different type of bit. I'm a rookie when drilling aluminum..

Thanks for the help in advance. ......................Krems

Evan
11-06-2007, 09:19 PM
Dry machining works well if you have chip clearance. If not then you need to use some lube and clear the chips regularly. Keep in mind that when drilling deep holes the chips have nowhere to go if the top of the flutes are buried in the hole.

Renegade
11-06-2007, 09:21 PM
Slow the speed down to about 500- 600 rpm and use lots of coolant or TapMagic ect. Being a newby I would also peck at it........ as in drill a little back out....drill a little back out , no drill can go it's entire depth with out backing out to clear it's flutes.

mochinist
11-06-2007, 09:21 PM
I've been playing around w/ aluminum lately trying to figure out the best way to drill a precision hole on a milling machine through 2 pieces (.75" ea. or 1.5" inches total thickness) of 2024 aluminum. Is there a proper way to dry machine aluminum. It seems that I get most of the way through and need to pull out to get rid of the chips. Id like to be able to drill to total depth w/ out pulling out of the hole. Is this posible when dry machining...What kind of RPM should I be drilling at...(1/4" - 9/32" hole size).....What about the feed rate. When the RPM was at 2000 the 2 flute bit packed w/ chips. Should I be looking at a different type of bit. I'm a rookie when drilling aluminum..

Thanks for the help in advance. ......................Krems2024 is soft and gummy, with a new sharp drill you could probably get away with one hole before the drill would start loading up and gettiing sticky, you dont need to flood it with coolant though, try either spraying it with wd-40, or apply kerosene with a small brush to the drill bit. A peck of about 1/4" will probably be best unless you get a parabolic style drill,

mochinist
11-06-2007, 09:23 PM
Slow the speed down to about 500- 600 rpm and use lots of coolant or TapMagic ect. Being a newby I would also peck at it........ as in drill a little back out....drill a little back out , no drill can go it's entire depth with out backing out to clear it's flutes.Gun drills can, they blow out the chips with threw the bit coolant.

darryl
11-06-2007, 11:59 PM
I'd say you got pretty far in before the chips packed. Probably too much to ask to get it through in one go.

J.Ramsey
11-07-2007, 04:20 AM
Gun drills can, they blow out the chips with threw the bit coolant.
Homer Simpson quote.........Doh.
How many people do you know that use a 1/4 inch gun drill to put holes in 1-1/2 inch thick Aluminum using a mill or a drill press?

DR
11-07-2007, 05:48 AM
Should I be looking at a different type of bit.


Try a parabolic flute drill. Some are advertised to go 10 times diameter with no pullout to clear chips. Get one with polished flutes.

What's your problem with having to pull out to clear chips? That's the way it's done in production.

krems
11-07-2007, 09:58 AM
I'm always looking for a more efficient way to get a job done. I don't have a problem pulling out to clear the chips. I would rather not if I could get away with it. I watched a video somewhere where the machine was drilling holes an inch deep w/ out lubricant and drilling to depth w/ out pulling out. I really don't want to be using lubricant on Aluminum if I can get away with it.

Looking at my drill bits I probably don't have enough chip clearance as compared to a parabolic bit. I am able to peck drill my way through w/ good results. I'll pick up another bit and give it one last try. I'll probably end up peck drilling w/ out lubricant.

Thanks!............Krems

mochinist
11-07-2007, 10:24 AM
Homer Simpson quote.........Doh.
How many people do you know that use a 1/4 inch gun drill to put holes in 1-1/2 inch thick Aluminum using a mill or a drill press?Your reading to much into it, I'm not suggesting to use a gun drill for this job, I was just debating what renegade said. "no drill can go it's entire depth with out backing out to clear it's flutes."


doh

Mike W
11-07-2007, 10:51 AM
Just use a little WD-40. Pull it out often to clear the chips. If you are careful, you will be using the same drill years from now.

carlquib
11-07-2007, 12:02 PM
A gundrill won't run dry for more than a very short distance, and drilling a hole in a plate like that would be interesting with the coolant coming out at 300+ psi it would have to have a complete enclosure. It is an interesting thought experiment though, but I think he asked about drilling dry which kind of excludes gundrills.

-brian

3jaw
11-07-2007, 03:52 PM
Is there any particular reason you want to drill aluminum dry?

You say that you are looking for a more efficient way to get a job done but drilling 2024 aluminum dry is false economy IMHO.
To do that will require you to slow down the RPM and the feed. Even then 2024 is so gummy that it won't take long for the chips to glue themselves to your drill bit. When that happens, you will have to stop and clean it or change drills. It will also leave the finish inside the hole very rough and messy!

These are the reasons why you see CNC machines shooting huge volumes of coolant on the parts and cutting tools. It's simply a matter of removing the greatest amount of metal in the least amount of time, i.e. Efficiency.

Squirt a little WD-40 or a good aluminum cutting fluid on it and be done with it.

Regards,
Greg

Evan
11-07-2007, 06:21 PM
2024 isn't gummy unless it's in the annealed condition. 2024 is aircraft alloy and is very high strength, nearly as strong as 7075. In the T3, T4 or T6 tempers which is how it is usually supplied it drills clean and crisp with almost no burr. Like 7075 it has a tendency on a deep hole to grab the bit so coolant helps a lot. Because the chips are hard they will jam and score the hole causing problems. It has the same tensile strength as mild steel and only 5% elongation at break.

It is usually drilled dry when drilling holes in thin material such as aircraft skins but coolant is recommended on deep holes.

3jaw
11-07-2007, 07:38 PM
I stand corrected on the gumminess of 2024 but I still stand behind my comments on using a lubricant.

krems
11-09-2007, 02:10 AM
Looks like my idea of drilling through the 3/4" - 1.5" aluminum dry is not working. I can't keep the hole finish clean and the bit keeps packing. WD-40 does wonders and just a little goes a long ways. I'll have to settle for squirting a little wd 40 on the bit for now.

Thanks............Krems

Scishopguy
11-09-2007, 12:23 PM
I don't understand why you need to drill a deep hole dry, unless it is part of an assembly that you don't want to get all gunky. Anyway, the best cutting fluid that I have ever found for non ferous metals is Relton's A-9. You don't have to flood it, just a tiny little swab on the tip of the drill will do a great job of keeping the metal from sticking to the bit. Peck drilling is the best way to not make a mess of it, also.

Just my $0.02 worth.

Swarf&Sparks
11-09-2007, 12:44 PM
pump-up garden or kitchen spray bottle, kero.
If you're drilling/boring don't spose it matters, but if you're turning, best finish is max speed you can get away with, zero rake tool, and kero.

If you want real flash finish, scotchbrite green :D

Evan
11-09-2007, 12:56 PM
Ethyl alcohol is the best and is used for high speed aluminum machining in industry. It has to be ethyl and it has to be 96% anhydrous. It leaves no mess and if that doesn't work then you can drink it. I recommend orange juice as a diluent.

Swarf&Sparks
11-09-2007, 01:00 PM
Evan, without a vacuum still, you're only get 96%. Even if you do have a vacuum still, the seond it hits atmosphere, it's gonna absorb 4% unless RH is zero!

Moral is, drink the ethanol, any flavour you like. Use kero for ali!

Evan
11-09-2007, 01:14 PM
The remaining 4% water is chemically bound. I believe the standard method to remove that 4% is to filter the ethyl through unslaked lime.

Swarf&Sparks
11-09-2007, 01:17 PM
And you're gonna drink it after that???? :eek:

Evan
11-09-2007, 01:29 PM
Whatsa matter? Afraid it will become poisonous? :D

Swarf&Sparks
11-09-2007, 01:40 PM
Well, mine comes off the reflux column at about 94%. That's good enough for me. Cut 50/50 with water, bottle it and call it vodka. After that, mix with tomato juice, ice, etc.

Disagree with the lime thing though. Ethanol is so hygroscopic, you cannot get better than 96% without a vacuum still, and as soon as you expose pure ethanol to atmosphere.......

Aint many places on earth with 0% RH ;)

Evan
11-09-2007, 03:53 PM
PROCESS OF MANUFACTURE
Absolute alcohol is an important product required by industry. As per IS Specification it is nearly 100% pure / water free alcohol. Alcohol as manufactured is rectified spirit, which is 94.68% alcohol, and rest is water. It is not possible to remove remaining water from rectified spirit by straight distillation as ethyl alcohol forms a constant boiling mixture with water at this concentration and is known as azeotrope. Therefore, special process for removal of water is required for manufacture of absolute alcohol.
In order to extract water from alcohol it is necessary to use some dehydrate, which is capable of separating, water from alcohol.
Simple dehydrate is unslacked lime, Industrial alcohol is taken in a reactor and quick lime is added to that and the mixture is left over night for complete reaction. It is then distilled in fractionating column to get absolute alcohol. Water is retained by quick lime. This process is used for small-scale production of absolute alcohol by batch process.


http://www.ethanolindia.net/molecular_sieves.html

oldtiffie
11-09-2007, 08:05 PM
Is this just up-market "moon-shine"?

And you drink it?

While your machining aluminium?

Why not "Brasso"? You can get pissed and polished at the same time.

And if you are hungry? Boot-polish on bread and butter.

How to brighten things up?

Easy.

"Techni-colour yawn" after drinking and eating that stuff - if you survive it?

Mad Scientist
11-09-2007, 08:46 PM
Try using “Tap Magic Aluminum Cutting Fluid”
You will never cut aluminum dry again; the difference is like between day and night.
www.tapmagic.com

And no I am in no way associated with Tapmagic.

Herm Williams
11-10-2007, 11:26 AM
I have have good luck using lard, next time you have bacon for breakfast save the grease for the shop, good use for a waste product. Imo it makes a good tapping/cutting lub.
re

Wirecutter
11-10-2007, 02:19 PM
Ethyl alcohol is the best and is used for high speed aluminum machining in industry. It has to be ethyl and it has to be 96% anhydrous. It leaves no mess and if that doesn't work then you can drink it. I recommend orange juice as a diluent.


I use the alcohol I can buy at Home Depot. It's called "S-L-X Clean Strip Denatured Alcohol." It works very well for tapping and drilling, and it's fairly clean. I thought it was ethyl, but I can't find it anywhere on the can. When I used in as windshield wiper fluid, it would make my car smell briefly like a drunk's breath.

Since it's denatured, you certainly can't drink it - the can says that it "cannot be made non-poisonous". There are a butt-load of other stern warnings on the can about how dangerous it is. But much to my surprise, it's very nice for use cutting aluminum - at least for 6061 and 7075.

-Mark

Wirecutter
11-10-2007, 02:22 PM
"Techni-colour yawn" after drinking and eating that stuff - if you survive it?

I always liked the term "round-trip meal ticket" :D

As for drinking denat alcohol and the incumbent unpleasantness, one need only ask Mike Dukakis's wife.

-Mark

Evan
11-10-2007, 04:49 PM
I always liked the term "round-trip meal ticket"

The technical term is to "review input".

Evan
11-10-2007, 04:55 PM
Here is some info on using ethanol as coolant.




http://datrontools.com/images/Ethanol1.jpg

Ethanol Coolant: Ethanol is a form of alcohol that results naturally through the sugar fermentation process and is environmentally friendly. It also happens to be an ideal coolant for high-speed, micro machining because a thinner-than-water viscosity allows the ethanol to quickly cover and cool more surface area on fast-moving micro tooling. The low evaporation point of ethanol makes it an efficient cooling solution and also eliminates the need for disposal and recycling, as well as their associated costs. Plus, ethanol coolants leave no residue on machined parts, which makes costly secondary operations, like de-greasing, obsolete — maximizing throughput, increasing efficiency and reducing labor costs.

Note: Ethanol coolant should only be used for machining of non-ferrous materials and Datron offers an oil coolant option for customers who machine steel-based materials.

http://datrontools.com/images/PDF_Icon.gif (http://datrontools.com/pressroom/WP_Environmental.pdf)