# Broken Tap



## HMeinhold (Jan 2, 2008)

Hi guys,


I started fabricating new larger cylinders for Betsy:

http://www.mylargescale.com/Communi...fault.aspx

I used 954 bronze and wanted to drill the holes for the cylinder covers before opening up the bore to avoid distortion. I was too lazy to make a fixture to align the tap, so I started one of the threads slightly crooked. Tap was a tiny 1-72 (about M1.6 for the rest of the world...). The inevitable happened: The tap broke. As I did not have any surplus stock, I had to save the part. This is what I did: 

#1 Clean the hole from oil and tapping fluid by "cooking" it in soapy water
#2 Simmer for about 10h (!) in a solution of citric acid. I happened to have this as pickling agent for silver soldering. It is available from McMaster or home brewing shops. The setup looked like this:










The reaction is OK, when a small stream of tiny bubbles escape out of the hole.
#3 The final result: The thread is clear:










#4 To avoid this in future I finally made the little gadget, which I should have done in the first place:










The bronze was not affected by the acid. Copper will probably react even less, brass may tarnish a little.
Hope this tip helps another desperate/unlucky soul!
Regards


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## Dan Rowe (Mar 8, 2009)

Henner, 
10 hours on simmer is a lot better than the application of the brute force followed by a do over method I have used a few times. 
Thanks for the tip. 
Dan


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## Steve Shyvers (Jan 2, 2008)

Hi Henner, 

When I saw the title of your posting I was going to recommend acid, but you were way ahead of me. Of course I've broken small taps only when tapping ferrous metal, so the acid cure to save the part wouldn't be useful. Acid will work for broken drill bits, too, if drilling long steam passges runs into trouble. 

Regards, 
Steve


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## D&RGW 461 (Jun 4, 2009)

Hi Henner, Thanks for posting the good info. I just recently broke a # 80 tap installing some brake rigging,I will use your method on it. It sure sounds alot better than a do-over like Mr. Rowe said. Thanks, Chris Sortina


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## xo18thfa (Jan 2, 2008)

So the citric acid dissolves the tap, is that what happens?


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## HMeinhold (Jan 2, 2008)

Posted By xo18thfa on 26 Nov 2009 08:07 PM 
So the citric acid dissolves the tap, is that what happens? 
Yes, exactly. Citric acid is very weak, it does not attack the bronze. It will not work on mild steel and I am not sure if it will leach out the zinc out of brass, though I have left brass in the pickle bath for a long time without problems.

Regards


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## xo18thfa (Jan 2, 2008)

Posted By HMeinhold on 26 Nov 2009 09:13 PM 
Posted By xo18thfa on 26 Nov 2009 08:07 PM 
So the citric acid dissolves the tap, is that what happens? 
Yes, exactly. Citric acid is very weak, it does not attack the bronze. It will not work on mild steel and I am not sure if it will leach out the zinc out of brass, though I have left brass in the pickle bath for a long time without problems.

Regards


That would have been the next dumb question: Does it work on steel. It's good news that you can recover bronze parts. Thanks Henner for passing this along


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## Semper Vaporo (Jan 2, 2008)

I always have the opposite problem... I break off a brass screw in a steel/iron part. An acid bath would only recover the broken screw!










I commented once that I used anti-acids to remove a brass screw from a steel part... No, I didn't put the parts in the anti-acid, I put the anti-acid in my stomach to quell the queasy feeling while I used a ball point carver in a Dremel Moto-tool to remove as much of the screw as I could and then used a tap to try to squish out the remaining brass from the threads (the part was of such a shape I didn't think I could hold it properly to drill the screw out.


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## HMeinhold (Jan 2, 2008)

Bob, 
it only works on stainless steel. With mild steel you could only retrieve the brass screw as Semper Vaporo mentioned,... 
Regards


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## armorsmith (Jun 1, 2008)

Gents, 

For removing a broken brass screw from a ferrous part, make the bath a caustic solution. That is how they used to (too many moons ago since cast iron motor blocks were rebuilt) clean the block of ALL non-ferrous material. If you left the copper backed cam bearings in place, they were gone when you got the block back. 

Bob C.


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## Dave F (Jan 2, 2008)

Phew.. you had me worried there for a minute.. Based on the thread title I though you weren't able to get the beer out of the keg... now THAT would have been disasterous..


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## armorsmith (Jun 1, 2008)

I had to do a little research, but Drano is a caustic solution. PLEASE be VERY CAREFUL - this stuff is dangerous. I would recommend wearing good rubber gloves (not the cheap ones for washing dishes) and a full face shield (available at a welding supply). Can be done cold, heating helps but is more dangerous. 

Bob C.


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## Semper Vaporo (Jan 2, 2008)

Posted By armorsmith on 27 Nov 2009 09:59 PM 
Gents, 

For removing a broken brass screw from a ferrous part, make the bath a caustic solution. That is how they used to (too many moons ago since cast iron motor blocks were rebuilt) clean the block of ALL non-ferrous material. If you left the copper backed cam bearings in place, they were gone when you got the block back. 

Bob C. 

???? You sure about that? Draino is put down sink drains and until this age of plastic there was a lot of brass used in drain pipes.


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## Greg Elmassian (Jan 3, 2008)

Actually, in my experience, the drain pipes were all cast iron, maybe you had some short sections from the sink to the cast iron system, but majority cast iron.. 

I think they also told you not to have standing water in your drain, the idea was to get the draino down to the clog. 

Regards, Greg


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## rkapuaala (Jan 3, 2008)

Great tip Henner. I wish I read this 6 months ago


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## Havoc (Jan 2, 2008)

Other solution is alum for steel in brass. 

For historic reference: over here the drains were lead, not iron.


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## armorsmith (Jun 1, 2008)

Semper, 

Actually, you are correct. The 'Tail Piece' - the piece that mounts in the bottom of the sink - the trap and the adapter piece to the main drainage system in the house used to be chrome plated brass. Depending on the manufacturer, some plated the inside as well as the outside. Being as these were easily accessed parts they were considered expendable, but were also the parts the home owner could disassemble to clear. Also if you read the precautions on the Drano can, it recommended not leaving the solution sit in the drain more than a relatively short time. (I never could figure out how you were supposed to remove the solution if the drain did not clear in the recommended time.) 

In the days of PVC, several factors come into play. PVC has a very smooth inside wall, nothing for stuff to catch and build up on. If you do get a clog, PVC is relatively impervious to most common acids and caustics, so choosing a chemical agent to break up the clog is much easier. Lastly, most of us have been educated (either by teachers or school of hard knocks) what not to put down a drainage system. 

Bob C.


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