Dissolving broken taps

[Lew_Merrick_PE]

As already said CHILL, we are talking about, maybe, half a teaspoons worth of not too concentrated Nitric acid, not buckets full. You will have to find your own equivalent to a teaspoon on the other side of the pond, but you should get the idea of the quantities involved.

Ned,  A suggestion of "70%" concentration was made.  That's a lot more than "not too concentrated."  I regularly work with hypergolic fuels, so my "measure" is fuming red nitric acid -- and I think accordingly.  Garden variety muriatic acid (15% concentration of HCl) sends several dozen people to the hospital every year just in western Washington because of inhaled fumes.  I was not hearing enough think safety in this discussion (at least as I see things).  Concentrated acids have dangers.  It is not "dangerous materials" that frighten me, it's people handling "dangerous materials" without having though things through that scares me.

[AdeV]

I was not hearing enough think safety in this discussion (at least as I see things).  Concentrated acids have dangers.  It is not "dangerous materials" that frighten me, it's people handling "dangerous materials" without having though things through that scares me.

Lew,

It's true that I've not handled concentrated acids since my school days, which is more years ago than I care to remember. It's also true that I'm not sure what acid dissolves what - I had absolutely no idea that Nitric acid would leave aluminium alone whilst dissolving steel, for example. Google helped there.

What I DO have left over from my school days is a very healthy respect for the dangers of concentrated acid, and the need to handle them with extreme caution. Not quite as much caution as you, perhaps, but I'm expecting that if you're de-scaling steel, you're using quite a lot more acid than I am...

[raynerd]

I regularly work with hypergolic fuels, so my "measure" is fuming red nitric acid

I can`t imagine the OP is working with the red fuming rocket propellant type! - I`m pretty convinced it`ll be good old white HNO3.

Garden variety muriatic acid (15% concentration of HCl) sends several dozen people to the hospital every year just in western Washington because of inhaled fumes.

It wouldn`t supprise me that the vast majority of irresponsible people were sniffing the stuff from the bottle! ... but I did hear that  87% of statistics are made up.  



Anyway...AdeV - any more progress today????

[John Stevenson]

... but I did hear that  87% of statistics are made up.  

I heard 88.67 but don't know how true it is ?

[Ned Ludd]

Hi Lew,
If you look back to when I mentioned using Nitric acid, in the form of "cartridge case cleaner", I mentioned no specific concentration. The Delway product is already diluted and the label says it can be diluted further by up to 90% with water. This I do not consider to be 'concentrated' or particularly dangerous. I remember one teacher at school using Nitric acid to clean a Brass fitting on a book and deliberately putting some on his finger to show how safe it was! Although I personally would not do this, as the thought of it getting in a cut makes me wince. You might only think in terms of exotic compounds used upper echelon technologies but WE are talking of commercial over the counter products. I doubt in this day and age of those-who-should-know-better's paranoia, that concentrated Nitric acid is easily available to the general public because of its use in things that go "whoosh-bang-ooh-nasty".

So, I repeat "Chill", and stop looking for the worst and start looking for the best. Credit some people with a little common sense, you might be surprised that the majority of the population can survive even without your education or experience, both of which I respect , but please keep it "real".
Ned

 

[AdeV]

Anyway...AdeV - any more progress today????

Not much to report at the moment, I'm afraid.... last time I prodded at it, there's still a chunk of tap in the hole.

I may have to move on to plan C: Buy a small carbide drill, drill into the tap, then use an easy-out to try to extricate it. Or try to tap the tap with a left-handed tap, if one can buy such things... [google] I see you can, why did I ever doubt t'internet... hopefully as the inner tap starts to bite, it'll simply rotate the original tap (what's left of it) out of the hole. Then I can finish the job with the proper HSS taps I've bought...

[andreas]

Well…I did it a lot of times but not on a tap, you weld on the broken stud/screw using stick welder very carefully till you make a welding buildup out of the hole. After you can weld there a nut and take everything out. Usually we use E312 16 electrodes. I hope this can help!!!!

Andreas

[Lew_Merrick_PE]

Guys,

AdeV wrote, "Well, you _can_ buy it straight off eBay, 1ltr @ 70% for less than £25 delivered."  That is what kicked my reactions into gear.

One of my longtime friend's wife is an ER nurse.  I had gone over to their house with a bottle of muriatic acid to help with some regrouting.  She just about freaked (not seeing my air supply system) as she sees people brought in suffering from acid damage to their lungs from using muriatic acid with fair regularity.  I agree that getting into that position qualifies as "dumb" if you have any idea what you are doing, but too many people do not know the dangers of things they can buy off the shelf.

I was visiting Guy Lautard (I assume most of you are aware of him and his The Machinist's Bedside Reader series) a few years back.  He had a small (plastic) bottle of concentrated nitric acid that he had wrapped in cotton balls and placed inside a larger glass jar on his shelf.  The cotton balls had turned into gun cotton and all the steel within a couple of feet of his "storage location" had been etched to a nice medium brown by the fumes that escaped the jar.  (A) Gun cotton (nitrocellulose) can be "highly entertaining" in the most unexpected ways; and (B) etching by acid fumes can reach into all sorts of areas where you do not want it to reach (hence my warnings against using it indoors).  The storage container was located about four feet from the headstock of his lathe.

The fact is that many of the things we do can be quite dangerous.  So long as we are aware of the dangers and take appropriate precautions, there is nothing wrong with this.  However, when I see "advice" accumulating calling for something like "70% nitric acid" coupled with "using it indoors," I think that a bit of, "Guys, think about this..." is not out of order.

[Bernd]

Very nicely said Lew.

Ok now guy's let's keep under control here.

Bernd

[raynerd]

                                                                                    

[AdeV]

Well, there was a blob of rustyness in one of the holes today... I guess it's working, then, just slower than I'd hoped... 

I've refreshed the acid, will leave it another day, repeat until done...

[AdeV]

A quick update: After leaving it a couple more days, there's more rusty snot appearing - this time out of both 'oles. Conclusion: The taps are dying! Slowly.... it has to be said, but shurely. Hopefully there'll be enough aluminium left at the end of the process to take a thread!

[raynerd]

AdeV - chemically it shouldn`t, but is the ally being affected?

[AdeV]

AdeV - chemically it shouldn`t, but is the ally being affected?

It's taken on a bleached appearance where the acid's been around... apparently concentrated nitric creates a protective oxide layer on ali (wheras dilute nitric will, in fact, dissolve it! Thanks to Ralph for that heads up...!). I don't think it's going to cause a problem for my purposes, but I'm definitely glad I've got some excess material to mill off the top...

[raynerd]

Nice one, didn`t know that and think maybe I should have 

[andyf]

Ade, are the broken taps out yet? It's been a fortnight since you were last cursing them.

Andy

[AdeV]

Ade, are the broken taps out yet? It's been a fortnight since you were last cursing them.

Not yet... I think it may be time for Plan B. I just need to figure out what Plan B is....

[Ned Ludd]

Are you sure you are actually using the right acid? You would have thought that by now your problem would be over long ago. As I said I dissolved a 2 or was it 2.5mm tap in a couple of hours.
You haven't found a source of stainless steel taps, have you?
Ned

[rowbare]

Ade,

Not sure of what the status is currently but since you didn't have much luck with the acid, this might work for you: http://pico-systems.com/edm.html

bob

[PJW]

Has anyone heard of using bleach to dessolve   broken taps??

[texta]

alum you should also be able to get from a chemist . i used to ( many years ago ) work in the factory that made the stuff . we made it mainly for the city council and it was used by them in water treatment . i used to eat the stuff every day and go home covered in it .
it is made from mixing bauxite powder , water and sulphuric acid in the correct ratio and order ,then it generates a hell of a lot of heat and foams up to at least 10 times in volume ( we would sometimes throw liquid soap on it to knock it back down a bit if it looked like over flowing the huge mixing pot ) then when the reaction is finished it was poured out at a very high temerature onto into a bay ( looked like wet cement at this stage ) then left to cool and set , then smashed up with boncats and fed through the crusher and milld to the required size granule .oh yeah it used to eat the titanium mixing paddle in the mixing pot over a few months of production and stainless steel disapeared in a matter of seconds .

johno

oh and dad used to put it in a hollow tooth to kill the nerve when he had tooth ache , this i can not recommend though cos i tried it and it aint nice , he told me it was a common fix for a tooth ache while at sea in the merchant navy .

[vtsteam]

The reason alum is available in grocery stores here is that it is used in making pickles crisp. I think it's found in the spices section of the store.

[PJW]

I got some alum from flebay, I had it a couple of weeks so it was time to try it. I made a strong solution in a cup then dug out the electric slow cooker then stood the cup containing the solution of alum with the offending alloy manifold with broken tap, I then surounded the cup with boiling water and turned on the slow cooker. I took about 3 hours or more to desolve the tap but it did, a bit to my suprise & joy. 
I have a lot of alum left, lets hope I dont need it!

[S. Heslop]

I've found alum in halal food stores. They're pretty good for finding some of the harder to get stuff, like citric acid and monosodium glutamate (the secret behind making pizza dough as good as the takeaway's).

[AdeV]

Gosh, this topic brings back memories...

Ned, if you're reading this - yeah, pretty sure it's the right acid (fumic nitric acid - it certainly fumed alright). It was having a go at the taps, I think the problem was, none of the acid was getting down past the shank, so the total surface area the acid was working on was only the top of the broken off piece. Hence the slowness to dissolve.

As for EDM/spark erosion machines, oh yes, I want one of those. Having seen awemawson's machine in another post elsewhere... Definitely want one of those...

Alum - interesting, I wish I'd known that, I'd have tried it as a solution.

As I never really finished this thread off, here's what eventually happened: I got fed up with the acid, and ended up milling a rectangle around the offending taps. Once I'd got low enough past the broken off shanks, I was able to extract them with pliers. I then cleaned up the holes, used the broken-off ends of a couple of old HSS cutters as pins (to hold the circular plugs in place), milled out a rectangular bung to go in the hole I'd made (I made it about 0.002" bigger than the hole), stuck it in the freezer for a while, then whipped it out & banged it in with a big birmingham screwdriver (er, hammer). Then, when it was properly gripped, milled it flat. You have to go looking for the join these days, which is nice