broken tap in aluminum cranckase

[goldstar31]

Paul
Oddly, if one puts iron and aluminium together, the reaction can act as a battery of sorts and certainly generates small amounts of electricity. However, forgive me, if you put rusted iron and aluminium fillings together- and ignite them , you get a bloody big explosion and this, believe me, is how some iron rails are joined and hopefully, will never happen in OZ, you have incendiary bombs. Don't try it because an ordinary hose will cause further explosions and needs to have a sprinkler system to cool the reaction.
How do I know all this? I was a kid in WW2 in the UK.

I was a bit baffled in the second para. I suspect that you were having a 'tongue in cheek' remark. I think that I understand the 'double entendre' LOL

Cheers

N

 

[Chris Murphy]

I have always thought aluminum alloys and zinc to be very reactive to strong acids and would think any concentrations of nitric, hydrocloric, and sulfuric acids would attack not only the ferrous tap but also the inside surface of the hole. I have personally used alum with good success but I don't remember whether my 2-56 broken tap was carbon steel or HSS. It might have made a difference. I had a good friend who was a noted gunsmith and he removed many broken screws but used a local water jetting company to remove his worst stuck screws. I have seen 4-40 sized screws removed, but I'm not sure just how small a hole water jetting can handle. I do know it was very cost effective and it cut rapidly.
Jeff[/QUOTE

Almost correct-except that aluminium is passivated against nitric acid-but not the other two mineral acids-using nitric acid to remove broken taps in aluminium castings works well-the other two not so well (-or to be accurate-the other two work-but at the expense of also corroding the casting-which is not usually a preferred outcome!) I've used 30% nitric for the job in the past-so slightly stronger than 'battery acid' to give some equivalency (and yes I know battery acid is sulphuric acid!) Commercial concentrated nitric acid (which is the way you would generally purchase it-is 67%-so you would dilute this a little over two fold for a working stock.
The only point of concern is that the process can generate some discolouration of the casting-but that depends largely on the alloy composition.....and hopefully there will be no need to immerse the entire casting in acid-if you're lucky with the location of the broken tap it is usually possible to build a dam using plasticene or modelling clay around the offending hole and broken tap to confine the acid to the vicinity-which reduces any discolouration to a fairly small area. In my cases the alloy was a high tensile casting with a significant Si content-and Si itself does react with nitric acid, and this reaction caused the discolouration. Needless to say-there is no need to entirely dissolve the broken tap, only as much as is needed to remove it-though in the case of very small ones, there is not much difference in the time required! ....and thorough washing after the process is done is required. A bit of baking soda or washing soda in the initial rinses does no harm either to neutralise any residual acid lurking in the threads.

 

[metalmudler]

Norman,

After making my own BP and fuse for fireworks, it was obviously the next step..
"Don't try it"... To late!

Had my fun . Grandfather worked on train lines, heard the stories.
Sadly not allowed fireworks of any kind here in OZ anymore I guess its the old story of the irresponsible people ruining it for the responsible people.
I can use the remainder of the bag to color cement, but what am I to do with left over tub of aluminium powder.
LOL Yes Norm, you got the second para mate

Paul

 

[Cogsy]

However, forgive me, if you put rusted iron and aluminium fillings together- and ignite them , you get a bloody big explosion and this, believe me, is how some iron rails are joined and hopefully, will never happen in OZ, you have incendiary bombs. Don't try it because an ordinary hose will cause further explosions and needs to have a sprinkler system to cool the reaction.

In the right concentrations and particle sizes what you describe here is called thermite. It isn't inherently explosive, although steam explosions are certainly possible when it is ignited due to it's extremely high reaction temperature. And while you're correct that a hose won't put it out, neither will a sprinkler. For open days at uni we set up a pot of thermite above a large clear tank of water and the molten iron generated by the reaction drops into the tank with such energy that some water is split into it's components, which ignites at the surface of the water - so effectively we burn water. It's a very impressive demonstration.
Thermite is still used for welding railway tracks together in some parts of the world (including some parts of the USA I believe).

 

[Dubi]

I taught myself enough chemistry up to Matriculation standard during WW2 and had a rather cooperative local chemist- who obtained things which we as boys shouldn't have had.

Having said that, you might Google something called 'Aqua Regia' . Interesting topic if you like that sort of thing.

Oh, and aluminium, I always thought that nothing more more than caustic soda held in a dam made from child's modelling clay also 'fun'

My father who was extremely clever but had no money used caustic to seal iron radiator pipes in the family greenhouses. Of course, caustic is useful to remove oil and grease PRIOR to starting to chemically remove iron.

The saponification of fatty acids things, if I recall distant days.

Just before the start of the Festive Season, I was on my way to family and wasted a bit of time before my train in the chemist's trying to get a styptic pencil. I got looks of utter horror and disbelief when one didn't know what I was talking about and the manageress came on the scene and recalled that her father had a 'cut throat razor'

It's fun be really old- and still completely with it! I suppose that I'l have to open a few cheap batteries.

Regards

Norm

Hello Norm,
A very Happy New Year to you and your family. Thank you for a very informative reply. I will certainly investigate Aqua Regia.

Your comment about Septic Pencil reminds me that my Mother always had one in the Medical cabinet in the bathroom but this was in the 1950's.

regards,
Dubi.

ps: As a kid I had great fun with Sodium Metal!!!

 

[Dubi]

Muriatic acid not nitric acid. I don't think you will find nitric acid unless you know where to look it is not sold anywhere. Muriatic acid comes in 29% and 40% either one will work I have used them both. It has a very toxic gas set up a fan to blow it away do not breath it or get it in you eyes. Muriatic comes in 1 gallon plastic jugs. Blow oil out of tap hole. Use gas to clean oil out of hole several times blow gas out with air hose too. I drop of acid each time. Do not blow acid with air hose and don't get it on you. When you need to clean acid out of hole use water. What size tap is it?

Hi Dazz,
Happy New Year to you and your family. So far lately we have not broken a tap in the workshop. Let us see what happens this New Year, thank you for the information.

warm regards,

Dubi.

 

[davesmith729]

alum works and it is safe

 

[mcostello]

I tried it on a broken tap for a week simmering on a wood stove and it did not work at all. I wonder if there is something to add to the mix to get it to start on a different type of metal tap, such as more included chrome?

 

[goldstar31]

I tried it on a broken tap for a week simmering on a wood stove and it did not work at all. I wonder if there is something to add to the mix to get it to start on a different type of metal tap, such as more included chrome?

Not wishing to be controversial but have you and others checked to see what your chemical was?
Again, large quantities of 'non iron' alloys might also affect reactions.
I have lathe tools that contain no iron whatsoever. On the other hand, I have rusting HSS lathe tools.

Intriguing, to say the least

Norman

Later, I was unable to find that Nitric Acid on my E-Bay list-- but sheafs of warning labels.

 

[John Roberts]

Still waiting for anyone who has successfully used Alum to tell us the ratio of alum to water? Thanks in advance.

 

[Gene Pizzoli]

Not wishing to be controversial but have you and others checked to see what your chemical was?
Again, large quantities of 'non iron' alloys might also affect reactions.
I have lathe tools that contain no iron whatsoever. On the other hand, I have rusting HSS lathe tools.

Intriguing, to say the least

Norman

Later, I was unable to find that Nitric Acid on my E-Bay list-- but sheafs of warning labels.

Are your lathe tools ceramic. What are they made of if not an Iron alloy

 

[goldstar31]

Are your lathe tools ceramic. What are they made of if not an Iron alloy

None are ceramic but quite a few are tungsten- which in its format are from mined.
Personally, I'm not unduly bothered as my problem( small and insignificant) is removing a broken screw on an three insert milling cutter.

For others, I was reading up George Thomas( Model Engineers Workshop Manual) and in addition to him using nitric acid he made up a trepanning tool in certain applications. What sort or how he made it was never written up. I understand the principle and have quite a lot of broken tungsten carbide drills which could be altered to form spade drills as I have quite a few assorted tool and cutter grinders- some with diamond and CBN wheels.

Again, my daughter who is a consultant dentist/orthodontist probably throws away lots of suitable drills- and I have a Dremel type drill as well.

However, I am cognisant of the fact that others have considerably less tooling than me- and I'm merely trying to add to the fund of helping

But Thank you

Norman

 

[Cogsy]

You want it to be a saturated solution so heat the water and continue to stir in Alum until it won't dissolve any more. Then keep the solution simmering away as it does its job. As some of the water evaporates away, the Alum will begin to recrystallise, so you will need to keep the water topped up.

 

[John Roberts]

Many thanks Codsy.

 

[Dubi]

Norman,

After making my own BP and fuse for fireworks, it was obviously the next step..
"Don't try it"... To late!

Had my fun . Grandfather worked on train lines, heard the stories.
Sadly not allowed fireworks of any kind here in OZ anymore I guess its the old story of the irresponsible people ruining it for the responsible people.
I can use the remainder of the bag to color cement, but what am I to do with left over tub of aluminium powder.
LOL Yes Norm, you got the second para mate

Paul

Be careful the Boys in Blue do not visit you.

 

[OldRon]

Does this discussion pertain to a thread cutting tap broken off in aluminum OR dissimilar metal and electrolysis?

IF stubbed off thread tap then having worked in several aircraft manufacturing machine shops I have seen plenty of that in expensive parts and the majority of the parts were saved by a tap burner. For those that are not familiar with the process then it is very similar to Electrical Discharge Machining, albeit crude. If the part is transportable then it should not be difficult to find a shop with a tap burner. Those of you that are creative and have a TIG welder could build your own tap burner.

"An Ounce of Prevention is Worth a Pound of Cure".

Switching from removing material to create a threads TO displacing material to form threads significantly reduces the risk of stubbing off thread cutting taps in work pieces and it improved the consistency of the thread classification. If you have CNC machinery that supports G02 and G03 with depth in the axis of rotation then from ¼' and larger thread milling is your best friend. I build my own 2 flute single point thread cutters on my CNC milling machine using the Machinery's Handbook to get the correct profile for each thread series. If the hole to be threaded is blind and it's large enough then I mill the threads. I would much rather chase threads than chase a stubbed off thread cutting tap.

I hope all ended well for the OP.

 

[metalmudler]

Be careful the Boys in Blue do not visit you.

Why would they? That was going back some time now, when I was a teen, not a middle aged man. That's why my previous post included acknowledgement of them/it being illegal. Thanks for any concern though.
I do not recommend anyone make their own or even possess them/it today in OZ.
Although new years eve, Sydney. There were still illegal fireworks arrests!

Still waiting for anyone who has successfully used Alum to tell us the ratio of alum to water? Thanks in advance.

Hi John, I used a saturated solution as cogsy described to remove a 2mm tap from a bronze cylinder flange (cant remember if it was carbon steel or hss). It was an open hole through the flange. I did it in a warm oven and kept the broken tap hole covered with the undissolved crystals in the solution whilest still submerged. It worked in a few days by loosening the tap pieces enough to pick them out with a pin.

 

[sedge]

There is a watchmakers product called Vissin made by Bergeon that might be worth investigating, should be available from horology suppliers.
Bergeon Vissin liquid was specifically designed to dissolve screws which have broken inside a watch plate, bridge or case. Item is set in a glass alcohol cup or appropriate container, cover with Vissin then heat. Bring to a slow boil, the liquid will eat away the broken screw and when a black substance exudes from the screw hole, you know the screw has been completely removed. Immediately rinse the piece under running water and clean with benzine. Use caution because the liquid can eat through more than just the broken screw you want to remove.

 

[mcostello]

I called the maker of the Alum and they told Me it was Aluminum Ammonium or some such, so I had the wrong thing. Will get the right stuff and keep it on hand. This may explain the many complaints from people who cannot get it to work.