# Chemical Tap Removal



## SAM in LA (Sep 1, 2010)

I recall someone posted information on how to remove a broken tap from aluminium using a chemical solution.

I did a site search and found one post which said to use a saturated solution of ALUM.

Can someone point me to the other posts on this subject.

Thanks,

SAM


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## Bill (Sep 1, 2010)

I don't have links to the other posts, but I recently used alum to remove three #4-40 steel screws that were silver soldered in brass about 1/4" thick. The holes were "through" holes.

I made up about 1 cup of alum solution in a ceramic cup (glass would have been better but the cup I had could accommodate my part so that the solution could get at all the screws - the cup was ruined in the process). I put the cup with the solution & part in a pan of water "double boiler" style, heated things to just below boiling. You'll see tiny bubbles fizzing away when it's working well. The reaction came to a virtual standstill whenever I stopped heating the solution. I had to add water every so often to make up for evaporation. I did this for short periods (a hour or two at a time over several days) I didn't keep track of the total time, but it might have been about 8-10 hours total. I just kept it up until all the bubbling stopped, and by that time all traces of the screws were gone. The brass was tarnished a little, but didn't appear harmed.

Bill


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## agr (Sep 2, 2010)

Sam,

This might be the information you are thinking about
http://www.homemodelenginemachinist.com/index.php?topic=6415.0

I have also recently used Alum (swimming pool "Flocculant") recently to remove a M2 tap from 6061 Aluminium. I filled a plastic container with hot water, tipped in enough Alum until no more would dissolve and then put it out in the garage. As Bill has mentioned, not much happens when the solution is cold - but it does happen!!. After about a week or so (after the first two days I forgot all about it till next time I was out there) the remains of the tap just fell out. I'm sure a constant heat source would accelerate the process.

Hope this Helps


Tony.


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## RollaJohn (Sep 2, 2010)

Another thread on this topic is HERE


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## SAM in LA (Sep 2, 2010)

Thanks guys.

Search terms. Broken tap removal, Chemical tap removal.

I'll look for Alum in the grocery store.

Also, Alum = aluminium potassium sulfate which can be swimming pool floculant.

I'll let you know what I can find in Lower Alabama.

Thanks again.

SAM


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## robwilk (Sep 2, 2010)

I also have had a go at the alum trick but after many hours heating it in a pan i gave up and decided it would be quicker to remake the part.
I am sure the process was working as i got lots of bubbles coming out the hole and lots of black sediment in the water from the drill bit but it was just taking ages .
So i think you need to offset the time remaking the bit to boiling it in a pan.
Also when i let the solution cool my part became encapsulated in a Cristal like over coat which is very difficult to get off without reheating.
Rob...


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## Lew Hartswick (Sep 2, 2010)

I use nitric acid when I beak a tap. Haven't done so lately so don't know where I'll
be able to scoff some up. Back when I was at the chem dept of UNM it was no 
problem. 
  ...lew...


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## SAM in LA (Sep 2, 2010)

So, how hard can it be to find some ALUM?

There must be some nefarious use for Alum, because when I asked at the pool supply store and local pharmacy, they wanted to know why I wanted it. Not that it is any of their business. I could get 50 pounds for $40 US at the pool supply store. The grocery stores and pharmacy's don't have it. I ended up ordering 1 pound for $10 delivered.

SAM


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## zeeprogrammer (Sep 2, 2010)

Spice rack in the baking aisle of your local grocery.
Comes in small bottles. McCormick.
Isn't that the same thing?


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## SAM in LA (Sep 2, 2010)

zeeprogrammer  said:
			
		

> Spice rack in the baking aisle of your local grocery.
> Comes in small bottles. McCormick.
> Isn't that the same thing?



Zee,

Here in Lower Alabama it is the end of "pickling" season so everyone is out of stock.

SAM


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## Kermit (Sep 2, 2010)

SAM in LA  said:
			
		

> There must be some nefarious use for Alum, because when I asked at the pool supply store and local pharmacy, they wanted to know why I wanted it. ...SAM



"What do you want if for?" they said.

"For free would be nice, but I'm willing to pay you for it" I answered.


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## techonehundred (Sep 2, 2010)

Just wanted to add to this. I broke a 10-32 tap in some aluminum which left a piece about 1/2" long in the hole. I bought the Mcormick version of Alum from the grocery store, then stopped by the local thrift shop and bought a small ceramic skillet(about 4") with a lid. I mixed a 1" cube worth of alum powder in about 3/4 cup water and simmered the water. After 1 hour, the tap was noticeably loose. then I added just a little water as it boiled(simmered) away, then in about 3 hours I could not find any sign of the tap other than some small rust granules in the bottom of the skillet. So I am sold on this.


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## jpeter (Sep 6, 2010)

I broke a tap in the aluminum block of the v8 you see in the heading. I was beside myself as to what to do about it. I found a web site suggesting burning it out with a home made edm. The electronics was simple consisting of a few items I had laying around and a variable power supply I already had. I think a battery charger could be used as a power source, or maybe a 12v car battery. Anyway, I made the tool from some brass and used my mill to guide it. Built a dam of clay around the blind hole to hold the liquid. I used motor oil for cutting oil. Had the tap burned out in 10 minutes. Had an amp meter in the circuit and downfed the stylest to keep the current at about half the max current. BTW, I tried a steel tool and couldn't make any progress. I tried water for a cutting fluid and couldn't make that work either. Its messy. The surprising parts was that the threads in the block were as good a if nothing had ever happened. A google search will bring up the site.


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## dsquire (Sep 6, 2010)

jpeter  said:
			
		

> I broke a tap in the aluminum block of the v8 you see in the heading. I was beside myself as to what to do about it. I found a web site suggesting burning it out with a home made edm. The electronics was simple consisting of a few items I had laying around and a variable power supply I already had. I think a battery charger could be used as a power source, or maybe a 12v car battery. Anyway, I made the tool from some brass and used my mill to guide it. Built a dam of clay around the blind hole to hold the liquid. I used motor oil for cutting oil. Had the tap burned out in 10 minutes. Had an amp meter in the circuit and downfed the stylest to keep the current at about half the max current. BTW, I tried a steel tool and couldn't make any progress. I tried water for a cutting fluid and couldn't make that work either. Its messy. The surprising parts was that the threads in the block were as good a if nothing had ever happened. A google search will bring up the site.



jpeter

Searching for EDM brings up a lot of links. I'm wondering if you could help me narrow it down a bit. I am sure that a lot of members would be interested in learning more about this as every week there is someone breaking a tap someplace. Thanks for your help.

Cheers 

Don


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## Lew Hartswick (Sep 6, 2010)

Yes jpeter, please do a sketch of the circuit you came up with and what did you 
end up with for an electrode?
  ...lew...


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## jpeter (Sep 10, 2010)

Sorry about the delay getting back. I lost the link and it took me a week to find it. This is pretty much what I used. For the AC capacitor I used a motor starting cap. I used a bridge rectifier instead of what he has and stupidly used no isolation transformer. I was just careful to not get grounded. I own a variac. I used my mill to plunge the tool. I set the down feed at about 0.01 per minute. I monitored the current and manually backed off the plunge when the tool would get shorted. I used sae10 non-detergent oil for fluid. I used modeling clay to build a dike around the hole to hold the oil. Its messy cuz strong sparks cause the oil to fly everywhere and the oil gets burned too and its hot and stinks. Water didn't work at all and neither did a steel probe. Brass worked well. I found turning the mill at a slow rpm helped eliminate shorting a lot. I adjusted the short current to about 3 amps and held the current during the plunge at 1/2 that, 1.5 amps, as best I could. After removing the tap, about 10 minutes of burning, I burned a 1/8 hole through a 12 inch file in about the same time. I also burned a hole through a #50 drill shank using a single strand of stranded wire for a probe. Had to reduce the current a lot for that experiment. That was pretty cool.
http://pico-systems.com/edm.html


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## SAM in LA (Sep 10, 2010)

My ALUM showed up yesterday.

I was able to dissolve 8 oz. of ALUM into 8 oz. of hot water.

When the solution cools to room temperature it becomes a jell.

When I think about it I place the jar in the microwave over for 45 sec.

The jell then turns back to a thick liquid.

I have not noticed any change to the 2-56 tap which is broken off into a piece of 6061 Aluminium.

SAM


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## techonehundred (Sep 10, 2010)

When I did mine, I put it over the lowest flame I had on the stove. It gives off a noticeable stream of tiny bubbles off of the tap when working. So the water must need to be almost boiling. So I would suggest going to the local trift store(goodwill or equiv.) and getting one of those glass stovetop pans and use that. It really worked well for me. So I think the temp is not high enough.


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## spuddevans (Sep 10, 2010)

dsquire  said:
			
		

> jpeter
> 
> Searching for EDM brings up a lot of links. I'm wondering if you could help me narrow it down a bit. I am sure that a lot of members would be interested in learning more about this as every week there is someone breaking a tap someplace. Thanks for your help.
> 
> ...



The latest issue of MEW has just started a series of articles on building your own EDM, might be worth a look.

Tim


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## Bill (Sep 10, 2010)

Sam,

I agree with Techonehundred: this should be done on a stove, keeping the temperature of your solution very near boiling (or at a gentle boil), and keep it that hot the entire session. Once the solutions is hot, you should see a stream of tiny bubbles emanating from the broken tap. The process still takes a quite while - even when the solution kept hot. 

My alum solution didn't turn to a gel when cold (there was some crystal formation I just added water until they dissolved again). The solution can't be so thick that it cannot enter the hole and make contact the broken tap. If your solution is that thick, you'll need to add a little more water to make your solution a bit "thinner". Then you need to keep adding water to your solution whenever it seems too think, or is forming a lot of crystals.

Good luck,
Bill


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## shred (Sep 10, 2010)

It took a few days at room temperature for me to get a tiny drill out of some brass with a crystallizing Alum solution.


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## rake60 (Sep 11, 2010)

I have an old fashioned electric hot plate that I use for the alum solution tap removal.

This one to be exact:






It was most likely made a few years before I was, but it works just fine for keeping
the alum solution just below a simmer on the back porch or basement floor.

It also eliminates the wife's objections to using her kitchen stove or appliances. 

Rick


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## SAM in LA (Sep 11, 2010)

Rick,

I put my jar in the oven at 190*F. The jar is sitting in a Pyrex pan for disaster containment. I did notice some bubbles coming from the hole with the broken 2-56 tap. I sure hope this works. The cylinder block was a lot of work for me and it came out on size in all dimensions.

SAM


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## Bill (Sep 11, 2010)

SAM in LA  said:
			
		

> I put my jar in the oven at 190*F. The jar is sitting in a Pyrex pan for disaster containment. I did notice some bubbles coming from the hole with the broken 2-56 tap. I sure hope this works. The cylinder block was a lot of work for me and it came out on size in all dimensions.
> 
> SAM



It will work - and you'll save your hard work. A blind hole would take longer than a thru hole. As long as you continue to see those bubbles the process is continuing to dissolve the tap.  It's a matter of choice whether to watch until the bubbles stop streaming from the hole (at which point all of the tap should be completely gone); or check every few hours to see if the broken portion of the tap will fall out/be flushed out.


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## robwilk (Sep 11, 2010)

I found it better if the hole is facing up i found i got more bubbles (more of a reaction) 

Rob


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## SAM in LA (Sep 11, 2010)

Boil and bubble, toil and trouble, disappear broken tap, disappear I command you!

 th_wav woohoo1

Spells by SAM


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## SAM in LA (Sep 12, 2010)

The tap is no longer in my cylinder block.

The ALUM worked as advertised.

I placed my jar in the oven with the lid screwed on loosly.

I set the oven at 200*F and within 6 hours the tap was dissolved.

Thanks for the information.

SAM


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## jpeter (Sep 13, 2010)

Did the alum have any effect on the aluminum, discoloration, pitting, etc.?


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