drilling aluminum

Is there a special type of drill bit for drilling extruded aluminum? I have some basic bits at home, but they don't seem to do too well.

Reply to
AE Todd
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Like Tom said, if you're having trouble the problem is most likely in sharpening the drill. AL drills great with a nice freshly sharpened drill bit and maybe some WD-40 or kerosene for coolant.

Are you experienced, or do you have questions, on drill sharpening?


Reply to
Karl Townsend

And (just guessing) maybe don't spin so fast?

Reply to
cavelamb himself

I am fabricating a hand truck. I need to drill some holes through the aluminum pieces to facilitate hinging action. I have a Ryobi electric drill and some basic Black & Decker drill bits. I was trying out the drill on some scap aluminum, and the various sizes seemed to be very slow at drilling. That is why I ask if there are special drill bits of a particular material or style that work on aluminum better or is there a special technique, like using oil at the point of contact. I don't see myself sharpening the bits I have. I was just thinking that I have the wrong bits for aluminum. Or maybe mine are just dull. That's an interesting quandary.

Reply to
AE Todd

If your bits won't cut aluminum, they've got to be VERY dull. Or you're using a very slow drill. Try a new bit. Had some older Bullet bits that were very good, current B&D stuff is pretty bad. Even Varmint American bits are better. Still, any of them should bite through extruded aluminum almost like balsa. Run them fast and use aluminum cutting fluid, kerosene works.

If you're using hardware store extrusions, these are gummy stuff and don't expect very much strength to them, they'll bend very easily. Design accordingly. Extruded aluminum can be made in heat-treatable alloys, I've never met up with any outside the motor home plant, though.


Reply to

Most of the stuff for my project came from an aluminum yard, out in the countryside. Tons and tons of aluminum in all shapes and sizes. I did have to get one piece at Home Depot though. I'll try just buying some new bits and use some petroleum product too. What exactly does cutting fluid or kerosene do to the process?

Reply to
AE Todd

As mentioned, aluminum is gummy and wants to "weld" itself the the drill bit. The cutting fluid stops the welding and clogging of the drill bit. When you take the drill bit out of the hole and see aluminum stuck on the bit, you know it's not cutting, but just trying to melt its way.


Reply to

Just a thought: Make sure the drill is turning in the right direction!!!!!

Many moons ago I sharpened the entire set of drills for a very good friend. I even tested a sample to make sure they were good.

What happened? He called me complaining that the drills were as bad as ever......

I knew this was not possible and asked him to describe his "drill press". Yup, reversible hand drill in a cheap stand. Throwing the reverse switch into "forward" helped greatly! :-)

Now then I HAVE been guilty of welding a band saw blade upside down through a work piece!


P.S.: Got that "new" VFD up and running on the little gear hobber. Nice. I think though that I still need to add a jack shaft reducer for hobbing steel gears. Also work holding mandrels. wfh

Reply to

In memoriam...

Subject: Re: drill sharpening FAQ? From: Robert Bastow Date: Mon, 11 Oct 1999 07:59:04 GMT

Intro snipped.....

The drill was ground, freehand, on the FACE of the wheel (not the flat side)...care being taken to keep the POINT angle as equal as possible on both sides..I'll tell you how to do THAT in a moment..

Lets do that now in fact..

Jim, You are dead right about not being able to grind a drill without mechanical help! Well here's how you create your own "6 Million Dollar Bionic Darex" ;^)

Let's assume we are going to sharpen a 3/8" diameter, 2MT shank drill..it is about 8" long (these figures are arbitrary..I just want every one to have the same mental picture of what I am describing. We approach the wheel, which has been dressed on its face, dead straight across with no grooves..(Ve SHOOT anyone ve catch putting grooves in ze drill wheel!!..No Pity..No Prisoners..Ya! Verdampt!)


The drill shank is held firmly in the RIGHT hand...ALL the movement and control is imparted by the RIGHT hand. For the purposes of drill grinding, the left hand could be...with benefit..a LUMP OF CLAY!!

It is from this "lump of clay" that we fashion the Bionic Darex".

Place your left hand thumb and finger tips LIGHTLY together..Relax the other three fingers aand let them naturally curl against the palm of your hand. Let the drill flute drop into the vee between thumb and fore finger and let the tip of the finger "Find" the curve of the flute where it fits comfortably. The tip of the thumb rests on the sharp junction ot the land and the flute, about an inch back from the drill tip.

Now...SQUEEZE HARD!!! YOUCH!...I said it would be easier if it were clay!

8^) Lift the drill from your fingers...see the GROOVE?...Drop the drill back in..it locates within a thou or two! Magic?..Bionic at least! Squeeze again to set the groove. You have created a customised drill guide that fits better that that on any machine ever built! You can relax your grip now..feel how smoothly the drill will ride back and forth, guided by the groove you have created for it.

Place the knuckles of your left hand, LIGHTLY on the ginding wheel tool rest, and swing the drill shank, from left to right (using ONLY your right hand) and push the drill lengthways though that groove in your fingers back or forth using the groove to make the drill twist or "rifle" in your fingers. Do NOT move your left hand in any way..it is made of clay remember!


A) The drill axis is "eyeballed" to be at half the required point angle to the wheel face...You can scribe or chalk reference lines on your grinder benchtop to help you line this up..at least untill it become almost second nature.

B) The drill axis is dropped JUUUst below horizontal. This will ensure that your soon to be ground drill lip will start with a "smidgin" of cutting clearance.

(Ideally, and certainly for a beginner, the grinder rest should be set dead radially to the wheel center and about half the drill diameter below the true center of the wheel)

C) The two cutting edges of the drill..the straight, sharp bits, formed by the junction of the flute and the back face (the only bit you grind), should be horizontally disposed..with the edge uppermost on the side closest to your left hand..the othe sharp bit of course, pointing downwards (Jeeze this would be a lot easier with a sketch pad)

This I will call the SET or START position!

NOW, move your left hand for the first, last, and ONLY time during th is whole exercise. GENTLY ease the cutting edge towards the spinning wheel, carefully maintaining all the angles and orientations of the SET position..until the cutting edge is JUST shy of touching the wheel. If you listen carefully you will hear the tone of the entrained air, whistling through the narrowing gap. You will hear a subtle but distinct change of tone JUST, I mean Just...a couple tenths of a thou BEFORE the edge touches the wheel. STOP!!! FREEZE!! DO NOT MOVE!!

Now, press the knuckles of your lump of clay..sorry, your left hand FIRMLY down onto, into and around the grinding rest..establish a "Groove" on the back of your hand as well as between your fingers.

We are now ready to grind, Your left hand locked to the drill and grinding rest is otherwise quite relaxed..letting the drill slide, twist and tilt wherever your right hand and the groove in your fingers tell it to go.

The actual grinding is a bit of an anticlimax.

You have previously studied a new drill point, you have read about clearance, and cutting angles, and rakes and......

With the RIGHT hand in control, gently, kinda, lean forward... bending or squeezing your arms hands and body..rather than actually moving them..untill you take up that last couple of tenths and the wheel begins to cut. Let it cut..don't force it, and dont' rush it..it really won't hurt anything if you take a full minute Per pass per face. YOU and your "Bionic Darex" are totally in control of that drill and the wheel..Forget the times when, close to panic, you swung the drill wildly past the wheel, hoping to get "the dirty deed" over with as quickly as possible.

Take your time, enjoy the moment, THINK about the shape you are trying to generate. Just the one face is left to "Interpretation"...every other aspect,angle, facet, what have you...Has ALREADY BEEN TAKEN CARE OF!! and is locked in place under your control!

The right hand should perfome a "Lower Quadrant sweep" for want of a better term..An observer behind you would see your hand move from about 17 minutes past the hour on a clock face, to roughly 25 minutes past. But it isn't a smooth arc of a circle, more a sector of an elipse..You see, as your hand starts to drop slowly, you are also rotating the drill in "the groove"..the first third of the turn needs to maintain that very slight clearance angle on the cutting edge, and not increase it too rapidly.

You need the clearance to cut..But too much at that point will WEAKEN the edge, and cause the drill to snatch and chip...So the first part of the rotation is ALMOST but not quite, just as though you were grinding a straight cone point on the end of your drill. Only as you approach the second third, does your right hand start to noticably drop..kinda "Catching Up" on the rotary motion...increasing the clearance as it does.

In the last third of the rotaion the right hand drops quite rapidly..Thogh not enough to catch the OTHER drill lip on the wheel..that lip is coming around quite rapidly by now.

Above all, take your time, if it helps, move the drill one degree at a time, and think ahead what shape or angle the next degree of cutting face needs...Remember, you have control, and IT ain't going nowhere 'til you decide.

After a pass on one face, flip the drill in your "Bionic Darex" DO NOT MOVE THAT LEFT HAND!!, return to SET position and repeat, the pass on the other face.

Having done a couple of passes on each face..it is now time to check the results on our homemade "Optical Comparator"

(Sorry Jim I couldn't resist!!) ;^)

Rest the center hole in back end of the drill shank, on the center point of the "Comparator" and use, first one and then the other drill lip to scribe a light line on your whitewashed (OK Blue or red dyed) surface.

You will readily see if the lines coincide..if the lips are even..or not, as the case may be.

Lets assume they are..Now look directly DOWN on the end of the drill to check the clearances. HUH? How can you check radial clearance by looking it staight in the face? Surely you need to look at it sideways?

Well no you don't...for once all thos interacting and confusing angle and faces and clearances are going to work together in YOUR favor and make what could be a tricky bit of metrology..quite simple. While we are looking at the end of the drill, we will also check that the POINT ANGLE is correct too!!!

(Ok guys, leave quietly..teenut has finally lost it!!)

No really, trust me. IF you look straight down on the point of a well sharpened, standard drill, you will see the two cutting edges, joined by the CHISEL edge which crosses over the web of the drill The angle fromed by the chisel edge to each cutting edge, should be ABOUT 50 deg...anywhere between 40 and sixty is ok for a first attempt. (I can hear the purists and theorists screaming and lighting up their flame throwers) But believe me, get it in that ball park and your drill will CUT. If the angle is too steep..you don't have enough clearance...negative clearance will give you an angle event greater than 90 deg. Too MUCH clerance and the angle will appear too shallow!

While looking at the end, check the point angle, How? Look down the axis of the drill at the cutting edges. Are they straight? If so, your point is pretty close to the right angle (As designed for that drill, by its manufacturer when he set the helix angle and the cross section of the flute) If the edges appear CONCAVE the point is too flat and if they appear CONVEX, the point is too "Pointy"

If your drill passes all these tests, which take but a second or two to perform, THEN IT WILL CUT..pretty close to size, without chattering, chipping, overheating, wandering or seizing. I guarantee it!

Hey, thats a pretty good start for the first drill you ever ground! All it takes now is a bit of practice for it to become second nature and almost as easy with a little 'un or a big 'un!

Hey guys!

My apologies for "goin'on" but If it helps just one person to pluck up the couragre and go hand sharpen his (or Her) first drill, by hand...

Then I hope you will bear with me.

It is late, I am tired and I am not even going to proof or spell check this,

'night all


Reply to
Karl Townsend

AE Todd wrote in news:1194311841.103097.197170@


If you are hand drilling, Pilot Drill it. I drill up to a couple hundred holes in aluminum with a hand drill on a weekly basis. Drill it with about a 3 mm drill first, then go to your bigger bit. Keep the RPM moderate on the small drill, and fairly slow on the larger drills. Keep a steady hand, and keep pressure on the drill. YOu will can see the sweet spot when you get 2 long curly chips coming out of the drill bit flutes.

Reply to

Sharp is good!

Reply to
Tom Gardner

According to AE Todd :

Hmm ... is that Ryobi drill equipped with a forward/reverse switch? Your description sounds like you're running the drill bit in reverse, and it is just wearing its way through. (There are also reverse drill bits, but I can't imagine a Black & Decker set being reverse -- you have to special order them if you need them -- and first you have to know that they exist. :-)

The quick check is that when the drill motor is turning in the right direction, the flutes will look like they're moving towards the chuck.

Of course, these days, B&D drill bits may be import drill bits, and those are extremely variable in steel quality. And if you have already used the bits on something else they may be very dull.

Also -- how fast is your electric drill? You don't mention its size -- and the larger the maximum size, the slower the drill turns, making it too slow for smaller drill bits.

Or -- if you go too *fast*, there is a build-up of gummy aluminum on the cutting edge -- especially if you aren't using some kind of cutting fluid. As others have suggested, either kerosene or WD-40 work pretty well as a cutting fluid for aluminum, though they are not good for steel.

Kerosene or WD-40 for aluminum are fine.

You need HSS drill bits -- with a conventional point, or even nicer, with a "split point". Drills for woodworking will be unsuitable. Something like the "spade drills" (flat ends with a spike point) are designed for woodworking -- as are foster type drills and several others.

How big are your holes? If they are 1/2" or smaller, and standard bits will fit your drill chuck, fine. If larger, you will need "Silver and Demming" drill bits -- bits with reduced shanks so the electric drill will hold them.

Depending on the wall thickness of the aluminum, perhaps something like a Unibit step drill will work well. Past a certain thickness, you will be working on two or more steps at the same time, so your hole will be multiple sizes. Most unibits will be good up to 1/8" thick aluminum.

What have they been used on before? If new, they should still be sharp. If used on hardened steel, they are probably dull. If used on masonry (bricks, concrete or the like) they will be useless for aluminum work -- especially so if they are the carbide tipped masonry drill bits designed for that -- and not for aluminum.

Well ... is it possible that you have bits designed for wood? Can you take some good close-up photos of the points and post them in the dropbox (check and read about how to use the dropbox. ) Once the images are there, post the URLs here (you can't (or shouldn't) post actual images to the newsgroup itself, but URLs pointing to the images are fine.)

The images should give us a better chance to identify your drill bits to see whether they are right for the material.

Good Luck, DoN.

Reply to
DoN. Nichols

I think the real issue is to start small and work up.

If a large drill is used to drive through - the central web at the tip doesn't drill a hole - the edge cutters do. So the big drill melts metal and then there is a mess.

Start small and slow - maybe build a dam and put water or coolant within. Drill out stepping up and then finish off.

It also goes for steel - but it doesn't gum unless you have a real bad drill and then you have a friction drill. Gets hot.


Mart> Is there a special type of drill bit for drilling extruded aluminum?

Reply to
Martin H. Eastburn

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