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Removing Broken M2 Tap from Anodised Aluminium 2014. Answered

Hello Everyone,

As you might have read, I have a Milled Aluminium 2014 Block which is Anodized with Black color, Today when I was tapping the holes of it, the M2 Tap broke and got stuck inside that hole, there is no portion of it outside the hole, so I can't unscrew it and pull it out.
I saw a few videos on youtube on how to use alum water, or electrolysis(with 10% dil H2SO4) to dissolve or chemically remove the Tap bit from the hole, But my question is is it possible that using any of the above options could destroy the anodizing on the job work. and is there any other easy method I can use?

Please Note that the tap bit is M2 and There are no tap extraction tools for a bit that small on the internet (or Locally Available in India) but if you find one Please post links for the same.

Please Be Positive and make this community a happy place. Thanks.


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2 years ago

Using H2SO4 WILL ruin your anodising. Sulphuric acid is used for anodising as it dissolves aluminium oxide and allows for thicker oxide layer (anodising). Acid in this process is diluted and formation of new oxide is stimulated with electricity. Concentrated sulphuric acid will strip the anodised layer very fast.

I know you have solved your problem already but just saying that in case someone with similar problem reads this later on


2 years ago

Hey Everyone, so after scratching my head for a while I decided to get it done by a professional, he is charging 0.2$/mm of height.
We also agreed to get all other taps done at a price of 0.4$ per Tap (the job work has a total of 25 taps).


Reply 2 years ago

That was your best idea!
M3 is a true pain in aluminium already, especially the better grades.
Even for that I prefer to make a little rig that won't allow any movement of the tap.
A tiny wobble, twitch or second of distraction and they snap right off you.
M2 is something that even I struggle with and I only use such small screws in materials I deem soft enough to tap by hand.
Extracting one that is broken off inside the hole is next to impossible without loosing your sanity.
I had some luck with three pieces of piano wire going through three holes placed like the slots on the tap.
But if broken off by twisting while bending this won't work as the tap is now jammed into the material.
The only thing I know that works here is a sensitve drill press and a left hand extraction drill.
But those hard enough to not just handle srews but also taps would cost you more than the entire job you now sorted out by professionals.

For better results try my way of making tiny tapped holes:
Get a drill set with fine increments, so for eample from 1mm to 5mm in 0.1mm steps.
Use some PVC, like from a downpipe, flatten it after heating and use this soft material for test runs.
Against commonbelief soft materials like plastic or aluminium can be much harder to tap than steel.
The material tends to curl up instead of breaking.
For M2 start with a 1.6mm hole, preferable with a drill press to keep it straight and the diameter even.
Make sure to go through slowly enough to not melt any material - you want the plastic come out in a nice string.
Now try to tap it without oil or lube, PVC is great here ;)
It should go fairly easy but if you look at the finnished cut with a magnifying glass you might see the thread is not properly formed.
If so try again but do less backturns with the tool.
Get a feeling how much material is building up and then turn it out completely to clean and go again.
Now you should see a much better formed thread but you might lack some detail.
Try again with a 1.7mm hole and to guide the tap use a few spins by hand with a bigger drill to smooth the top of the hole.
If you now (using the last way of cleaning instead of just breaking the cut material) get a thread that looks just fine try a screw in it.
It should hold reasonably well considering the soft plastic.
You can dare to go go 1.8mm in PVC but it should be fine with 1.7mm.
Aluminium is a different beast and here the prefered drill size is 1.6mm for a 0.4mm pitch and 1.55mm for a 0.45mm pitch.
Using 1.65mm for the first mm of the hole will make the start of the tapping much easier, if you can afford a mm.
I prefer sweing machine oil for these tiny jobs.
So fill the hole and wet the tap and use the same extraction technique as on the PVC.
If in doubt take it out ;)
Every time you do, clean out the hole and fill it with oil again.
If through hole use a piece of sticky tape to cover the underside.
As soon as you feel too much tension you take the tap back a quarter of a turn.
Try again and if still too much tension to half a turn back.
In case you already made three full turns you might have to take it out already, especially during the deeper parts of the tapping.


2 years ago

Several yrs ago, I was faced with a similar problem. I chose to drill and tap another hole in a location that it would work. To some extent, this meant accepting the Aesthetics of an abandoned hole with a broken tap.

If you're really committed to getting that tap out,


2 years ago

Do you have a spare piece of anodized Al which you wouldn't mind messing up as a test?


2 years ago

The only way to get the tap out is an acid that does not attack Al.. When I worked for Bill Lear of the steam bus fame, they regularly removed taps from Al blocks with acid.. I do not remember if it was sulfuric acid nor if it was safe on Anodized 2014.