# How extract a broken #49 drill bit in Aluminum



## Bill Kahn (Dec 2, 2017)

This must be one of the very most common beginner questions.  Please refer me to any previous threads that talk about this.

I was drilling a blind .9" long #49 hole in a 2x2x1.1" rectangular piece of aluminum. (Using my mill)  First one went fine.  In second the bit snapped off deep in the hole.

Is there any way to save the piece?  (No other location for the hole will work.)

Thanks.

-Bill


----------



## Dabbler (Dec 2, 2017)

This is  always a tough one.  So... I've put my kevlar on, so start shootin'! 

There is a cost/benefit to consider here;  the amount of work and cost in the part versus the amount of work and cost to save it.  There may also be an intangible benefit of additional experience in redoing the work. 

Commercial companies remove drill bits and broken taps by eroding them - a speeded up EDM process - BUT - in such a small hole damaging the sides of the hole is inevitable.

Here's the save analysis:  Aluminum will expand much more than steel at elevated temperatures.  If by heating it to 250 degrees F,  it doesn't fall out or move with a fine piano wire hook, then the tip is stuck with wedged swarf.  Your piece is then toast no matter what you do.  Why 250?  because this is getting dangerously close to altering the characteristics (temper, heat treat) of the aluminum (assuming it is 6061).

I hope this 'helps'...


----------



## petertha (Dec 2, 2017)

Sorry to hear that. Dabbler beat me to the oven / expansion trick so I will proceed to another friendly suggestion you might receive involving boiling the part in a solution of saturated alum powder to eat away at the bit. Even some YouTube videos showing it working. 

I broke a tap in a 2041 part & had a horrible time with that particular extraction method (link below). It may well be related to the tap composition/coating. But my own opinion: depending on a bunch of variables such as how badly stuck, how much swarf packed in the flutes, the type of  drill, availability of alum & suitable boiling vessel... start working on the new part  
http://www.homemodelenginemachinist.com/showthread.php?t=26470

I find peck drilling method + those high angle fluted drills + lots of WD40 or aluminum friendly cutting fluid works best. Small drills are very sensitive to run out so if your chuck jaws are sloppy, that invites problems. When you do the calculation for ideal speed your mill is probably on the low side if its anything like mine. Good luck.


----------



## kd4gij (Dec 2, 2017)

First I would try banging it hole side down on a piece of wood. I have about 80% success with that.


----------



## Ed ke6bnl (Dec 2, 2017)

I have always herd that you can put a dam around the part and soak the part in a solution of alum it will desolve the steel and not the aluminum. I have some alum powder but have never tried it and it is a slow process.


----------



## RJSakowski (Dec 2, 2017)

Was this going to be a through hole?   If so, you can try drilling from the back side.  When you hit the broken drill, you may just pop it loose.  if not, take a piece of piano wire slightly smaller than your drill size and gently try to tap it out.  If the exit hole size isn't critical, you can use a larger drill which will improve your chances of properly hitting the broken drill.


----------



## petertha (Dec 2, 2017)

This doesn't help your extraction problem, but its an interesting subject to me. Like how gun barrels are drilled etc. Your #49 drill is .073 diameter, so at 0.9" penetration you are dealing with a 12.3X depth : diameter ratio. There are all kinds of tables out there, maybe you will find some specific to aluminum which is sticky stuff.

If there is any way to re-tool your design so you don't have this issue, that would be optimal. If it is what it is, then there e are some specialized drills out there, this is one link I saved.
http://www.guhring.com/Documents/Catalog/Drills/DeepHoleFlyer.pdf


----------



## rwm (Dec 2, 2017)

Alum will work but Nitric acid is faster. It will dissolve the steel and not the aluminum. Neither of these is particularly fast!
Robert


----------



## kd4gij (Dec 2, 2017)




----------



## Mitch Alsup (Dec 2, 2017)

I used alum to remove broken 4-40 taps in aluminum.

In order to get useful removal speed, the alum needs to be supersaturated and near the boiling point of water. Depending on the size of the piece, find a container that you can put on the stove double boiler style. Over the course of 2-3 days, you are going to be adding water to the double part of the boiler rather regularly, and adding triflings of water to the alum part containing the piece under bit-removal less regularly.

Last time I did this, the part fit in a glass glass, and I set the glass in a typical fry pan with 1.5" of water on a low boil. When I was done, I left the glass cool off and within a day the rest of the water in the glass evaporated and I have a complete glass of crystalline alum left in the glass. It looks like all I have to do next time is to add about a shot glass of water and a bit of heat to get the alum liquid again.


----------



## jlsmithseven (Dec 2, 2017)

carbide end mill straight down


----------



## EmilioG (Dec 3, 2017)

How would you hit a .073" drill from the other side dead on? Even with a DRO this would be a hard trick.
This is one reason I like to use quality drill bits. Small number drills especially. Small holes, I start them with stub drills
or aircraft drills with cutting flutes only on a short part of the length. A broken drill in aluminum is a tough one.  I don't see
any way of getting it out without ruining the hole. Carbide is brittle and the hole too small to evacuate chips. Good luck and let us know
how it works out for you.


----------



## petertha (Dec 3, 2017)

I'm not sure if this is 'the' calculation, but maybe indicative of significantly higher rpm's required by small diameter drills than what typical mills & drill presses are set up for. http://www.carbidedepot.com/formulas-drilling.htm

I suspect chuck/arbour runout can start to be a bugger too. If your jaws are gripping say +0.002" out & the arbor is another 0.001" out, that 0.003" translates into 1.2%D relative to a 0.250" drill, but 4.1%D on the little #49.

I found this pic of a cool high speed quill side attachment somewhere in my travels & there are similar ideas out there. I believe its sitting at Project #124 in my queue


----------



## Eddyde (Dec 3, 2017)

RJSakowski said:


> Was this going to be a through hole?   If so, you can try drilling from the back side.  When you hit the broken drill, you may just pop it loose.  if not, take a piece of piano wire slightly smaller than your drill size and gently try to tap it out.  If the exit hole size isn't critical, you can use a larger drill which will improve your chances of properly hitting the broken drill.



I have done this trick except with a smaller diameter drill from the back side, used a pin punch to knock out the broken drill, then completed the hole from the front. 
If it cannot be a through hole, the back hole could be plugged closed.


----------



## RJSakowski (Dec 3, 2017)

EmilioG said:


> How would you hit a .073" drill from the other side dead on? Even with a DRO this would be a hard trick.


It is difficult to hit dead on.  But we are talking about how to salvage an otherwise ruined part.  I have done this on a number of occasions with success.  I will drill a smaller diameter hole from the backside to allow me to clean up the final hole like Eddy said.

One way to center the hole would be to drill a hole in a piece of stock and insert a pin in the hole and into the partially drilled hole in the work. Clamp the work in place and you should be fairly close to centered.


----------



## Karloss (Dec 3, 2017)

I always take broken stuf from aluminium by putting it to boiling vinegar for 3-5 hours.


----------



## TXShelbyman (Dec 3, 2017)

Could you drill a larger hole, press in an aluminum rod then mill flush??? Don't know how pretty it needs to be or if this would even work. Just a thought.


----------



## EmilioG (Dec 3, 2017)

TXShelbyman said:


> Could you drill a larger hole, press in an aluminum rod then mill flush??? Don't know how pretty it needs to be or if this would even work. Just a thought.


That's a good idea.  I don't know how strong the part needs to be, but a pressed in aluminum plug may just be the answer.
Once it's sanded, you won't even see any lines. You can even add epoxy to the pressed in "plug", and if it's a tapered plug, you can mill off the top flush. Aluminum is very forgiving in many ways.


----------



## Bi11Hudson (Dec 4, 2017)

TXShelbyman said:


> Could you drill a larger hole, press in an aluminum rod then mill flush??? Don't know how pretty it needs to be or if this would even work. Just a thought.



I just want to comment that the above comment should help me with a similar problem, albeit smaller. I often work with an alloy known as "zamak", which is Zi, Al & Cu. (the castings are for model building).. I have to drill a hole on the order of 0.047 to install a brass square piece of 0.047 rod. This is a high mortality operation on a die casting that is no longer available. Since aluminium is so tenacious and is a large part of the alloy, I purchase the bits in quantity. And the parts cannot be soldered, of course, they must be press fit.....The castings are not thrown away (not in my shop!) and this offers a system of recovery without heat.

I appreciate it, greatly. The aluminium is close enough to zamak that with proper dressing will be unnoticable under paint. When I ever get around to painting, of course. Mostly I just use chemical blacking and go on.


----------



## Bill Kahn (Dec 16, 2017)

Hello.  I am the OP.  Thank you everyone for all the ideas.  I have now tried them all.


Shake/tap to see if it would fall out.  Didn't work.
Drill in from the otherside.  I have a DRO and had it all well jigged.  No problem to be just about perfectly on target. Came in from the other side.  Being careful. Hit the old bit.  Bounced around there for a minute pecking at it. And snap.  I now have two drill bits stuck.  So, didn't work.
With the arbor press and a pin, just push hard.  Got it all lined up.  And 1 ton of pressure.  Nothing.  Didn't work.
Line up the pin carefully again and hit it with a hammer. Hit harder. Didn't work.
Heat it up--20 minutes full blast with a heat gun.  Do the above again.  Didn't work.
Buy 32 ounces of Alum (food grade even).  Equal volume of powder and water.  Seriously saturated solution.  In wife's oven, double boiler style, for 3 continuous days. 200F.  Adding water to solution and bath as needed (2ice a day).  Didn't seem to me the solution was circulating very well down in the tiny hole.  Still plugged up solid.  Aluminum has a different surface finish now. (I was going to do a final skim pass anyway, so, np).  But, still plugged.  So, didn't work.
Carbide drill bits came.  ($6+ each). Seemed like it was slowly grinding away the stuck bit.  Then, something clicked deep in the hole.  I am guessing the carbide got stuck between the old bit and the eroding aluminum wall.  And, as little bits do, particularly carbide, snap. The hole has been so worked by now the carbide bit did not stick.  So, didn't work.
As hole is no longer usable anyhow, first suggestion has risen to the top.  Start over.
I think I am going to practice drilling small holes in aluminum before botching up another piece I have 8 hours in.

Thank you for all the ideas.

-Bill


----------



## Bob Korves (Dec 16, 2017)

First rule about dealing with broken drills (and taps):  Be really careful not to break them in the first place.  It often a long fight trying to get them out, and work is damaged or ruined, with much time lost.  A lot less time is required to carefully study the best way to drill or tap the hole you have in front of you, to really understand how to make a good hole or thread in the material you are working with, than to try to fix the much bigger problem after the tool is broken off in the work.  The hurrieder you go, the behinder you get -- in my experience...


----------



## EmilioG (Dec 17, 2017)

One solution is to use smaller drill chucks with sensitive feed shanks, like the Albrechts.  and see:


----------



## EmilioG (Dec 17, 2017)

I've also read good things about the Omega Drill for drilling out broken taps. May also work for broken drills.  I've never used one. A straight flute carbide drill seems like a good choice.  You would need a very rigid set up on a mill.


----------



## magicniner (Dec 17, 2017)

EmilioG said:


> I've also read good things about the Omega Drill for drilling out broken taps. May also work for broken drills.  I've never used one. A straight flute carbide drill seems like a good choice.  You would need a very rigid set up on a mill.
> View attachment 250042


I'm loving that, it's so realistic


----------



## markba633csi (Dec 17, 2017)

Haven't broken a drill or tap in a long while but I know how the peck drilling fatigue sets in and you start taking deeper pecks, especially difficult on
powerful machines that don't give much sensory feedback-  Then SNAP! oh cr*p
Mark S.


----------



## Cooter Brown (Dec 17, 2017)

this is your solultion!

<iframe width="560" height="315" src="



" frameborder="0" gesture="media" allow="encrypted-media" allowfullscreen></iframe>


----------



## Latinrascalrg1 (Dec 17, 2017)

Can YOU share what the part is that has the broken bits in it that you are trying to save? Doing so will give us a better idea on how to deal with it.   Im thinking if you could use a larger left-turn cut drill bit to clear the hole by making the hole bigger thus giving you better access to the broken bits and then you can plug the hole by pressing in some aluminum rod as described above would probably be the best current option if that is an option!


----------



## EmilioG (Dec 19, 2017)

The Omega drills are # 4 on a list a good solutions., EDM being #1 and Walton tap removers almost useless.*( according to an expert).
Luckily, I've never broken off a tap or drill in an important part. I did break a few cheap import 1/8" bits from Home Depot at work.
Using a correct chuck size to the drill size, I feel, is key. Albrecht!


----------

