# Which drill bits for thick aluminum?



## milkyspit

The other day I got myself a nifty Craftsman drill press! Woohoo! /ubbthreads/images/graemlins/party.gif

Then I attempted to drill two small holes lengthwise through a half inch long piece of aluminum rod, and managed to complete 0 holes, but break 2 drill bits in the process. /ubbthreads/images/graemlins/banghead.gif

Am I just a moron? What's the trick to drilling holes through a thick piece of aluminum, folks? /ubbthreads/images/graemlins/confused.gif

It seemed like the bits stopped "digging" out aluminum particles once they got to a certain depth, and would just sit there and spin. The aluminum, meanwhile, got VERY hot. I tried gently pulling the bit out a little, then easing it in again, but that didn't help. I tried putting a little more downward force on the bit, and that didn't help either.

If there's a special technique for drilling good holes in stuff like this, I'd sure like to know it! Anyone care to share?

And what sort of bits will drill the best/easiest/cleanest holes through aluminum?

Thanks all. /ubbthreads/images/graemlins/bowdown.gif


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## cy

Try a good sharp bit and lots cutting coolant/lubricant. A lathe would ideal for what you described. I've had better luck going with a slower speed. This would depend upon the size of the bit. Maybe someone else could elaborate on rules of thumb.


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## McGizmo

Slow speed and you need to pull the drill up and knock the Al off the bit. Al likes to load up on the cutting tool. You might find that a cutting oil and some pressure with low speed will do the job for you. /ubbthreads/images/graemlins/icon3.gif


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## Tom_Ayers

IME, so-called cobalt bits usually work better for hard-to-drill metals like stainless and gooey aluminium. TiN coated are a little better than plain or phosphate coated in aluminum. Proper cutting lube, as noted, can help a lot. Once you weld aluminum to the cutting edge of the bit, it won't cut worth a hoot.

Twist drills do not give you a consistent, circular hole - sorta trochoidal shaped. You may want a reamer if true-size and perfect circularity is the desired end effect. Or make D-bits...

HTH,

Tom


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## mrsinbad

I have not drilled very large holes in thick aluminum, with the practice I follow when I drilled small holes in thick aluminum is too use a relatively slow speed with lubricant, and I make sure I clear any aluminum chips in the drill bit by backing it out several times during the drilling operation.


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## KC2IXE

As everyone here says - a relatively low speed will help, as you ar not doing production work

2)Proper lube - this is a BIG thing
3)Peck drilling - pull the bit ALL the way out to clear the chips - this is a GOOD time to add more lube

Lube has 2 jobs - 1) allow the chips to slide up the flutes - this is also what things like TiN coating help, and 2) cooling the cutting edge - the low speed helps keep this cool too

One thing you didn't mention - How big is the drill bit, and how deep is the hole? The size of the stock doesn't mean much

Any time your hole gets more than about 4 drill diameters deep, your starting to need to do peck drilling and the like

If you are going to drill a LOT of aluminum, you may want to get bits for AL - they usually have a slightly different point angle, AND they have a high helix - aka, they clear the chips faster. Another option is parabolic flute drills - these drills are great, except for one detail - they break fairly easily under ANY side load - you REALLY need to clamp down your work, center punch and spot drill your starting point, and THEN drill - all without moving the work

If you are doing REALLY deep holes - say more than 8 drill diameters, your either going to have to peck a LOT, or look into specialty drills if you are doing prodcution work - things like coolant fed bits, or for really deep holes, single lip, straight flute "gun drills" - but then your into stuff that even many machine shops outsource to places that specialize - think about this chalange - drill a .3 +- .001 hole 36" long and come out on the other end within .001 of center


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## Tom_Ayers

Yeah, what KC said...

WRT coolant/lube - emphasis on "proper" for aluminum. Darn near anything works to some extent drilling mild steel, but aluminum can be a real PITN sometimes. And if you've already welded some aluminum chips to the drill tip, forget it - change bits. Absent purchasing specialized stuff just for fooling around with a drill press, try a few household items. Sometimes flooding with WD40 works (if you don't press too hard) - more as a coolant than a lube, but watch the heat (ignition). ATF can work; sometimes kerosense; sometimes 50-50 ATF and Kerosene. Find out what works for you.

If you're not mentally prepared for the mess of drilling and clean-up with coolant and/or lube... well, don't wear a nice shirt... shop aprons seem to reduce the severity of the beatings I get from the laundrymeister... 

Some tips: Get some cakepans at a garage sale and fixture them up on the table and/or underneath the foot of the press. Drill holes in 'em if you need to - a scrap of innertube under the bolt head makes a good-enough gasket. 

If you have a couple of scraps of acrylic sheet, you can rig up temporary or permanent spatter-shields - BIG help in confining the mess.

Shop vacs can only do so much... you'll also need rags for clean-up. Cloth is fine; blue paper "shop rags" work great also. Don't leave any oil-soaked rags of either sort piled around for days (can we say "spontaneous combustion"?)

Fixturing the work for a drill press can be almost as involved as for a vertical milling machine - or, if you're careful and clever, fairly simple. Accurately end-drilling a relatively short cylinder in a home drill press is not hard to do (within the precision capabilities of the tool) if you do a little set-up first - I could sketch it for you much easier than trying to write about it...

IMHO, the first accessory you should get is an appropriately-sized X-Y table or vise for the drill press - opens a whole new world to simple drilling operations. Some of the cheap ones from places like Harbor Freight can be tweaked pretty nicely without much effort - but they also can be pretty darn bulky and heavy for most table-top drill presses. Matter of fact, I'm machining up a really nifty one from 6061-T6 aluminum scraps in my spare time for my buddy because the cast iron one he has is about as heavy as the whole drill press...

Have a blast with your drill press -- hehehe, let us know the first time you do bodily harm to yourself with rapidly rotating work stuck to the bit... but DO wear proper wrap-around eye protection (had metal bits removed from my eyes TWICE - I was a slow learner...)

HTH,

Tom


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## gadget_lover

Ditto on the eye wear! I had a copper metal shaving embedded in the iris (colored part) of my eye. It drove me crazy all evening long. I could not see it on the mirror.

The symptom was weird. It did not bother me when I was looking at things that were close to me, but was very irritating when I looked at anything more than 3 feet away. 

24 hours later, the doctor explained that it had oxidized, and that it had to be buffed out. The scarry part was him saying, "Now don't flinch, or it may cause permanent damage." Yikes!

So, wrap around glasses that are ANSI rated are a MUST. I never want to go through that again.

Daniel


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## KC2IXE

RE Cutting Fluids for Aluminium

The BEST is "original" tapmagic, but that stuff is rare as hen's teeth

The new formula tapmagic isn't half bad, particularly if you get the formula for Aluminum

One thing that works suprizingly well - get yourself some "Lye soap", and make up some VERY VERY soapy water - for Aluminium this works great (and smells like tapmagic - Hummmm.....)

BTW A small can of Tapmagic goes a LONG LONG way - I get almost a year out of a small can in my home shop. I usually try to go to Eastec - free samples


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## milkyspit

Wow. Thanks guys. /ubbthreads/images/graemlins/blush.gif Let me clarify what I was using. The drilling THICKNESS (not stock diameter) was roughly 1/2 inch, and at first I was trying to use a 1/32 inch bit, then a 1/16 inch bit. One of the bits I broke (the 1/32 inch one) was a Dremel drill bit of unknown type (gold color if that helps), and the other (the 1/16 inch one) was a Black & Decker High Speed Steel bit (dull black color).

And I wasn't using ANY lubricant. /ubbthreads/images/graemlins/frown.gif

Could you folks please elaborate on the types and sources of lubricant? Also, possibly a dumb question, but how is it applied, and how frequently while drilling... every few seconds, once or twice, ...?

I'd also like to learn more about these alternative bits. For instance, do reamers come in diameters as small as 1/16 or 1/32? What about these D-bits, etc.?

I've noticed one thing: my Unibit, which has a cutout all the way down one side, drills GREAT holes! But it's completely useless for deeper holes like the ones I wanted to drill the other night, because the depth of any given diameter on the Unibit isn't even remotely deep enough to go through the stock.


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## wasabe64

Scott,

WD-40 works well for drilling aluminum at low speeds (as mentioned above). Tap magic aluminum should be available at a good automotive/tool supply shop. 

When to apply the lube: from the start, on the tip of the bit itself. Apply a little more as soon as a cavity has been formed by the drilling (letting it pool in the cavity). A half inch is a long way for a 1/16" drill bit even with lube. KC mentions peck drilling, this will be a must for the depth you're drilling. If you are using WD-40, you could re-coat the bit every other pass since it will be consumed faster than tap magic.

Reamers are used for boring holes in work where more precision is required. The reamers will bore perfectly round consistent holes, within 0.001 of the reamer's rated diameter (over or under, your choice when you buy the reamer). Remember, you will pay for that precision, reamers are specialty tooling. 

Unibit - I think they call them step drills around here. They are convenient, but for very shallow work such as drilling sheet metal. 

HTH


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## KC2IXE

[ QUOTE ]
*milkyspit said:*
Wow. Thanks guys. /ubbthreads/images/graemlins/blush.gif Let me clarify what I was using. The drilling THICKNESS (not stock diameter) was roughly 1/2 inch, and at first I was trying to use a 1/32 inch bit, then a 1/16 inch bit.

...snip...

Could you folks please elaborate on the types and sources of lubricant? ...snip...

[/ QUOTE ]

OK a 1/32 diameter hole 1/2" deep is a bear, no matter how you slice it. Forget what I said about running slow for that - you have to run a bit that small fairly fast, BUT it has to be cooled, your going to have to peck, and your drill press can apply enough force to shatter that bit!!

Look into a "sensitive" drill press or drill press add on - you'll be able to FEEL what is going on.

The 1/16" is a bit better

Even there, 1/2" is a LONG LONG way to go - it's 8x the diameter of the bit. One option you MIGHT consider is drilling some larger size - say, 1/4" part (most) of the way through, then switch and drill the rest of the way with the small bit

Lubes - that small - yeah, your best bet will probably be something like Tapmagic for Aluminium. Almost ANY machine shop supply house will sell you a can - they will also sell you GOOD drill bits - let me put it to you this way, there are some seriously bad drill bits sold with "good" names on them - In industry, you'll find out that people like Black and Decker don't make drill bits /ubbthreads/images/graemlins/ooo.gif

As for machine shop supply houses - MY personal favorite is MSC (MSC Home Page) and my second choice is Travers Tools - and sometimes I'll go to Travers because I can drive to their main warehouse in about 15 minutes. Enco (which has been owned by MSC for the last few years) sometimes has good stuff, but also sells cheap import junk - you have to know what you are buying

Looking at MSC (NO affiliation except that I buy stuff from them)

Tap Magic for Aluminium - 4 oz can - P/N 00262337 - $2.09 
For a good grade of 1/16" drill bit, I'd say a Chicago-Latrobe HSS Polished finishe Production grade bit - Not the best (hey, you could spend a bit more and get Cleveland Twist Drill)

That bit is PN 81171043 and will cost you $1.02 each for 1, but it looks like you'll have to buy a package of 12, so they are $0.66 each

You might just want to buy a good drill SET (look at the web site)

Another option, as I said, was parabolic flute drills
PN 80901044 for CL brand ($0.99) or PN 78510153 
for "Precision Twist drill" ( a well known brand) for $1.35

You may also want to look into "High performance" bits like "Triumph Twist Drill" PN 00647529 which are $1.68 each (Might be your best bet!)

There are trade offs - for instance, all the "High perfomance" and parabolic flute bits can't take side loads - ditto carbide - and side pressure - "snap" - and beside, a GOOD solid carbide 1/16" drill bit will run you about $30 - EACH

Just to give you an idea of what's out there in the way of drills, look at The Guhring web site


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## mahoney

You still have to drill an undersized hole to use a reamer, in my experience they only enlarge a hole to their rated diameter.

To get really good cutting lubricant for aluminium, you will have to go to a machinery supply shop or order from some place like ENCO, McMaster-Carr, MSC, Grainger, ... but most of the lubes suggested will work fine.

As for when to apply lube, You want to keep a little bit at the drill tip at all times. If it's a critical hole, I apply a drop with each "peck". If I am not at the top or bottom surface of the material and the chips look like little chips rather than shiny spirals, either I need more lube or the drill bit is dull, or both.

A sharp bit is essential in soft materials like aluminium and you can also alter the cutting edge angle to optomize the bit for soft materials, but this might be tough on a bit as small as 1/16".

Also, it is not uncommon to break a bit when drilling a deep small diameter hole. It doesn't take much going wrong, push too hard, fail to clear chips, vise shifts a little, piece shifts a little, and "ping", that's it. Fortunately the bits are fairly cheap and so long as it breaks above the surface where it's easy to remove...no problem.


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## tvodrd

All good advice here!! For applying coolant, try a poly squeeze bottle with a 1-hole rubber stopper with a cut-off acid brush stuck through it. You can brush away chips from the drill/cutter while lubing/cooling it at the same time. At work we use CoolTool II fluid exclusively except for the rare case when we need flood coolant with the lathe. I recently drilled 2 .025" dia holes 1/4" deep for a "board assembly fixture." (Doesn't count cuz it was in delrin. /ubbthreads/images/graemlins/grin.gif )
(Don threads telephone poles before breakfast as I recall!)

Larry


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## Tom_Ayers

Scott,

If you have a local supplier of machine tooling, go shopping...

ENCO has lots of things like this LPS product Tapmatic #2 for aluminum or this LPS product Tapmatic #1 Gold for all metals 

You may find this sort of thing from numerous other suppliers - virtually all of them are on the web nowadays. I buy bits and pieces from several places around the country, depending on what I need, who has it for best overall deal, etc.

The size & depth holes you want to drill are not going to happen easily at first. You will have to withdraw the bit VERY frequently and even with lube you'll get chips packing the flutes. Keep a small stiff brush (a cheap toothbrush may work) handy and if the flutes are packed, sweep down the bit with the brush while it's spinning. If that fails, stop the press and use a pointy object like a dental pick to slide the swarf down and off the bit.

Smaller bits should be run at higher rpms - it's about tool speed, not rpm - hom many inches/minute is the cutting edge moving on the aluminum. Too slow is not as good as just right. Lots of lube, high rpm (on a home drill press), and light pressure will make clean holes.

Use a small oil can or a plastic syringe to keep the hole flooded. It helps to have a third hand operating the cutting fluid and bit-cleaning tools - that's why spiffy set-ups have automatic coolant/fluid delivery. Mist systems are very economical and Little Machine Shop (among others) has a very inexpensive small mist system if you get sucked into more chip-making later on (You'll need compressed air at ~30psi for a misting system - more toys, er, tools). But flooding works better for hole drilling than misting.

Again, I suggest you get a decent bit(s) - the hardware store/home improvement store brand name cobalt bits are MUCH better than the TiN (your gold bit) or steam oxide (black) for drilling stringy stuff like aluminum - you won't believe the difference (they have better point geometry as well) - look on the package for words to the effect of "...for difficult to drill metals like stainless steel..." The TiN coated bits are great for carbon steels and less expensive than cobalt bits - but you need better than TiN for little holes in stringy aluminum.

Get 3 common sizes: 1/4", 1/8", and 1/16" (better get 2 of those). Practice a few holes with the 1/4" at about 1/2 - 3/4 max rpm and lots of lube. When it works the way you think it should, switch to the 1/8" bit and kick the rpms up. Rinse and repeat. Then to the 1/16" bit...

Did I mention... got to your friendly local salvage yard with a 5 gallon plastic bucket, leather gloves, and cash? Pick out attractive bits of aluminum cut-offs. Get them weighed. Got back to scrap pile and take out the ones you can live without ("I had NO IDEA it was 45 lbs of aluminum in that bucket!!!"). Go back to checkout and pay for your scraps. Home and practice...

BTW, if you were trying to drill into a piece of soft, expensive hardware store aluminum rod - that stuff sucks to work with compared to 6061 or 7075. Get the good stuff cheap at the junkyard...

Yes, reamers are available in all sorts of sizes, flutes, etc etc. First you drill a slightly under-sized hole, then you ream it to finished size. There are other methods, but that's pretty simple and quite accurate. I'm guessing you don't need that sort of accuracy right now.

Have a blast...

Tom

*EDIT* - Wow! Three posts while I was pecking this out - all three GREAT advice /ubbthreads/images/graemlins/bowdown.gif, and all of the sources mentioned are places I use as well as others. Uh, I should have been more specific on the bits - ditto on the B&D type brands - but for occasional projects I get good bits at a couple of local hardware stores - if you're not sure what the brand is but if the (relatively) high price shocks you, yup, that's probably what you're looking for - much cheaper if you order from a supplier, but hey, it's instant gratification when you just broke your last #57 bit... *END EDIT*


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## idleprocess

Are any of the brands normally stocked at, say, Home Depot or Lowe's any good? I've always been leery of B&D, but when I see names like DeWalt and others that don't see Wal-Mart shelves for more than B&D, I'd tend to favor those.


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## KC2IXE

Some of the hardware store brands are tolerable, but most are junk.

Do yourself a favor, order a catlog from MSC or Travers tools - make sure to get their sales fliers. Next time drill bits are on sale, buy a set of "production grade" bits - preferably made in USA. They will run you about $45 for a set if 1/16" - 1/2" by 64ths. SOMETIMES you can get some good import stuff - if you know where it's imported from - I have some great bits I got from Poland right after the iron curtain fell - dirt cheap - turns out it was the top name brand on the other side. Stay away from "Made in China" or Made in India (China is usually BETTER)


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## gadget_lover

I (finally) picked up some end mills from Harbor Freight. The 4 flute set is dirt cheap, but enough for my modest needs. I used one last night in the tailstock of
my lathe to drill a hole in a reflector that I'd just turned. I could not have been happier with my $19.99 for set of 10 purchase.

It was fascinating to watch the long curls of aluminium emerge quickly and smoothly from the flutes of the bit. 

Daniel


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## McGizmo

I believe it's been mentioned before but the comment about driling through the reflector brings this tool to mind again. If you need to trim, de-burr or open up a hole, like in a reflector, there is nothing cleaner than a Uni-Bit or similar drill bit! For holes in thin sheet metal or plastic, you also can't find a better tool that will give you a round hole and if you kiss the edge of the hole with the next step up on the shoulder of the bit, you get an instant clean slightly chamfered edge.


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## lambda

I've had very good luck drilling 3/32" holes through 1.16 inches of solid aluminum using a Teflon oil for lubricant. Never broken a bit yet, and have drilled several hundred holes. I place 1 or 2 drops about 1/4" up the flutes from the drill tip and usually only need raise the bit three or four times near the end of the hole to clear chips. 

The Teflon lube is available in most auto stores as a general purpose oil, comes in small tube with 1" needle on the end for dispensing.

I use low speed also, even though the 3/32" bit is fairly small to prevent the dreaded aluminum melt. I've also drilled 1/16" holes through the same thick aluminum, but it's three times the hassle. If you can get by with 3/32" it makes the job much easier as the bit is just plain stronger.


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## SenorLuce

An old trick I learned back in school was to put a small patch of t-shirt material soaked in teflon lubricant between the bit and the metal to be drilled. clears a nice hole with no burs.


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