Tapping broken taps (a.k.a. I'm all tapped out)
 

I was recently asked to remove a broken tap from a plate of aluminum, where it had broken off in the bottom of a hole. Not wanting to manufacture a whole new part, I wanted to remove the tap without damaging the piece.

Larger taps (1/4-20 and larger) can be removed relatively easily. Tap extractors are available from Small Parts and other sources that work by sticking little “fingers” down the flutes of the tap and allowing you to back out the broken piece. For very large taps, reverse screws can be inserted into holes drilled in the end of the broken piece, and used to back the piece out of the hole.

But sometimes the tap may be too small for these to work. If you break off a small tap in the bottom of a 3/4” hole, you can use an old machinists trick to remove it. Steel taps will dissolve in a solution of alum and water. If the part you are working on is aluminum or some other non-ferrous metal, you can dissolve out a broken tap. Here is how:

Step 1 – Place about 1 quart of hot water in an aluminum or glass bowl. Do not use a cast iron or steel pan! Remember – you are going to use a solution that dissolves steel!
Step 2 - Dissolve alum in hot water.
Step 3 – Drop part containing broken tap in dissolved alum and water.
Step 4 – Heat gently (just below simmering) – the solution will work at room temperature, but works better when heated
Step 5 – After 1-2 hours, remove from water and shake out remaining pieces of tap.

Alum is available at chemical supply houses if you are going to buy a whole lot (i.e. you need to dissolve an entire ’68 Chevy engine block that has been sitting in your living room since last summer). Alum is used to make pickles, and is also available at food supply wholesalers if you are willing to buy 10 pounds at a time (you just want to dissolve the steel parts from your little brother’s bicycle). You can also find it in small quantities (1-2 ounce jars) in the spices section of grocery stores, if you just need a little to repair one or two pieces. In general, the solution is contaminated once it is used. So if you break a second tap a day later, make up a new solution and start again.

-dave

p.s. Important Lesson learned: DO NOT use your spouse’s expensive aluminum Calphalon pans as the “heating vessel!” The alum solution will very effectively remove the anodizing from the pans and leave bare aluminum. The pan is then useless for preparing food. This will be made clear to you in no uncertain terms. You will then have to take your spouse out for dinner at an extremely expensive restaurant. The total cost of this dinner will be at least four times the cost of a new Calphalon pan. You will realize, too late, that if you had just bought a cheap new pan to use as your “tap removal pan” to begin with, you would have saved a lot of money. Stupid you.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

How funny that you post this right now :) Earlier this afternoon I was teaching a team member how to tap when they broke off a 10-24 tap in a piece that took hours to machine. If we can't find any other way to extract it, we will certainly try your tip!

Thanks a lot for such good advice Dave.

Cory

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

A long time ago, I used a different kind of extractor that was like a drill bit with left-handed flutes. You put it in a tap handle. At first, the extractor just drills into the tap. Eventually, the flutes bite into the tap and the tap will start turning. I haven't had to use one of these in a while so I don't know where to find them.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

Dave,
This is the first time I heard of the Alum trick. Pretty cool. On the second one, that is a pretty tough fix. I wonder if Tom Edison had to put up with that?!? You would think that restaurants would kind of spread the word so they could drum up some business.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

That really must be some potent pickles. Though I wonder how those people found that out. Opps I droped my tap in grandma's pickles.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

$@#$@#$@#$@# i wish i knew that before. we broke to taps in out shafts and only had enough to replace one. i was so POed that i took it to a grinder and still couldnt find the bottom.

BTW would this meathod be safe on the axel shaft that comes in the kit??

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

My guess is that it would ruin the shaft and eat it away as well.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

thats what i was afirad of

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

:ahh:
:ahh: :ahh: :p

I tried your method and failed! But perhaps I got something wrong...

I first broke a standard 4-40 tap in a 0.092" aluminum hole (actually one of my teammates did).

Then I was excited to finally have the opportunity to use alum and dissolve the tap. Since the part was quite small, I filled up a pepsi can (with the top cut off) with boiling water, and added in about a teaspoon or tablespoon of alum. I then mixed it up, threw in the part, and waited. When I came in today (after a full night of the alum doing its thing), I couldn't get the tap out, and it still seems to be the same as it was.

So, I'm thinking of two possible errors:
1) I didn't put in enough alum (what are the correct proportions of alum to water?)
2) The water quickly cooled to room temperature... Maybe I should keep it boiling like the instructions say.

Any input would be appreciated!! Thanks!

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

NIce tip. I'll have to remember that for next year.

Anyways, speaking of cool metal related tips and tricks, does anyone have a good way to remove rust and corrosion from nuts and bolts, or large pieces like car body panels - in case you do want to finally take a chance at fixing up that '68 Chevy Engine that is sitting in your living room - (or '79 Mopar 360 as it may be in my case).

I was thinking just buying a cheap barrel tumbling kit from the craft department of the local store for the nuts and bolts, but will that work?

Is there a chemical way to remove rust and corrosion that would be faster, or easier - more for the bigger parts that won't fit in a tumbler?

I don't mind using a little (or a lot) of elbow grease, but if I can just let things get clean overnight in a solution of whatever, or in a barell tumbler, then that would be great.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

Carbonated drinks are supposed to be able to remove rust and corrosion.. but I haven't been able to test it out yet. The CO2 is supposed to react with the oxide that forms the rust, thus restoring the metal to its original state.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

I saw this thing on a show called Trucks! that was like a big bowl of nut shells or something and it vibrates a lot and you put your parts in there and they come out real nice after like a day. I think it was pretty expensive though.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

There was an episode of mythbusters that tested all the differnt myths related to colas. I don't remeber the results though.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

if i recall corectly, soda does remove rust and grease (to an extent) but not as well as rust and grease removers

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

An ultra sonic cleaner. Usually used with jewely.

The problem with mechanical means of removing R&C is that you actually remove material. They won't fit together as well any more.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

The truth behind this "urban myth" is the soda doesnt remove the filth, its mainly one ingredient in the soda that wil clean filth. This main ingredient is Carbon Acid. When you try to clean with soda, you gave the sugars, dyes, additives and syrups that will go onto what you try to clean and thus its dirty once again. When you use plain carbonic acid or really old soda (where the ingredients have broken down and carbonic acid is still there), you will get a clean surface and it will help prevent future deterioration. So if you are looking at cleaning it with a "soda bath" i would reccommend going to a beverage distributer and seeing if they have any plain carbonic acid that you could purchase. Other wise i would suggest you going a different route and first try a pressure washer with a degreaser or cleaner.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

So carbonated water is the best bet?

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

I heard Hydroxic Acid works really well.




j/k LOL sorry, couldn't resist.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

I hope that you aren't referring to the dreaded H-O-H....
:rolleyes: + ;)

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

You can still find places that "Hot Tank" parts for you - which depending on your part is either an acid bath or caustic. I had an engine block done about a month ago. Saw an episode of "Overhaulin" wher they acid dipped an entire car. Galvanizing places usually have a huge hot tank.
For home use there is Naval Jelly - been around for years and works pretty well. For bolts and small parts I use a grinder and a wire wheel, these throw off the bristles pretty well so make sure you wear a face shield.
But the best is a sandblast cabinet and is enviromentally friendly.
Word of caution when using chemicals of any kind. Make sure you know the hazards before you proceed. Look up the MSDS for that material on the internet or find an expert ( and then check the expert to make sure they told you right). Acid and Bases can create strong exothermic(heat releasing) reactions.
Ken

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

Carbon acid?? Are you sure it isn't carbolic acid? Also I just checked and there are a variety of acids in soda but nothing that starts with a C. Opps. There is an acid that is formed when carbon dioxide is in solution. Is that what you are thinking of.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

I mant to type carbonic acid, check later in my post, later in that sentence and you will see thats what i meant. Carbonic acid will form and remove many forms of oxides, including Calcium Oxide.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

You want the alum solution to be pretty well saturated. The last time I needed to do this, I dumped the entire container of alum - one of the little ones from the spice rack in the grocery store - maybe three ounces? - into about a pint of water. Heated it up to simmering, dumped in the part and walked away. It worked just fine, and after a few hours the part was tap-free.

That is exactly what it was. Vibrating bowls are used to provide a number of finishing operations for metalworking. A number of different materials are used, based on the finish desired or the rust/scale/crap to be removed. Ground walnut shells and fine playground sand are two of the more common materials. Left in the vibrating bin long enough, ground walnut shells will provide a nice polish to most metal parts.

[EDIT]There is a simple tumbler design here that will work very well for cleaning and polishing small parts.[/EDIT]

Ultrasonic cleaners will work real well to remove grease, oil and even old paint. They ususally don't do so well will rust and scale.

If you are specifically looking to remove rust, there are several ways. For small parts, or light rust, several methods already mentioned (Naval Jelly, steel wool, sandblasting, etc.) work quite well. If you have a lot of items to de-rust, or it is very deep into the part, you can try rust removal by electrolysis. For this method, you place the iron/steel part in an alkaline solution, pass an electric current through the solution, and blast some of the ferrous oxide back into good metal (you hope). There are good instructions on how to do it here and here. I have used this method once, and have a friend who does this a lot when restoring old machine tools, and it works quite well. And, yes, the resulting solution really is as nasty looking as that crud in the second link...

-dave

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

Hmmm... If you really want to use something like carbonic acid in large amounts why not get dry ice. It's easier to use.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

.. Dry ice is CO2 and carbonic acid is H2CO3, though. They wouldn't react in the same manner. In fact, dry ice would sublimate way too quickly to have any kind of reaction with a metal oxide :o

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

Carbonic acid is CO2 dissolved in water. Thus dropping dry ice into water will form the acid. I have seen this done before though I never knew that the acid was strong enough to do anything.

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

Yeah, that's true, I thought you meant just direct application of the dry ice :p . Plenty of CO2 gas would escape, though. To make the weak acid a little bit stronger and thus more effective for the reaction.. one could increase the solubility of CO2 in H2O by altering the temperature/pressure of the room, I believe




Whoa. Yeah. On the topic of dissolving broken taps, couldn't one find an ion solution in which the ions had a greater (or lesser? :confused: ) standard potential than the ions of the metal used for the tap, but a lesser (or greater?) standard potential than whatever material is being used for the robot? And then just pour that solution over the tap for a redox reaction?

Re: Tapping broken taps (a.k.a. I'm all tapped out)
 

alteing temp or pressure will work.

a lower temp allows more gas to disolve in a liquid and a higher temp allows more solid to disolve in a liquid.

I cant think about pressure now though... brain is too tired.