I Broke a Tap

[Jack]

This afternoon after spending the best part of a day making one of the pieces for my new project. Squaring up the piece, getting it to the right thickness, drilling seventeen holes and milling two pockets and then taping about twelve holes (2 5/40 and 4 4/40 threads) I broke the 4-40 tap on the last hole. Maybe I was getting tired or over confident.

Well I had a 3/16" piece of a 4-40 tap broken off in a through hole in a piece of aluminum, Don't you just hate it when that happens. Well I remember hearing about the "ALUM Trick" I went to the grocery store and got a little bottle of McCormick Alum (in the baking and canning dept.) mixed it, put it in a glass bowl on the gas stove with the flame as low as possible and after about an hour I took it out and rinsed it off and the remaining little chunk of the former tap fell out. I saved the little blackened piece of the tap as a reminder to take it easy next that I have some hand tapping to do.

IT WORKS, color me amazed :bow: :bow: :bow:

 

[Sshire]

Jack
How much alum to how much water?
Sounds like something to keep at hand.

Thanks
Stan

 

[Maxine]

Just last weekend I broke a #43 drill off in a Demon V8 block that I am making and I have been wondering how I would get the busted brill bit out ever since. I have never heard of this trick but it sounds like it could be just the ticket. Does it leave the aluminum unharmed?

 

[Chriske]

I found this on the internet.
I'm not responsible if anything happens so please be careful....!
Did not try it myself, did not broke a tap ever....

Tap Remover
Use at your own risk
This recipe has been used to remove broken taps from aluminum and stainless steel (300
series) with success in the past. Your results may vary.
Important- Follow these instructions carefully since you are dealing with dangerous
chemicals. If the chemicals are mixed in the wrong order an explosion may result. The
author is not responsible for any injuries or damages caused from using this information.
Anyone mixing or handling these chemicals is cautioned to proceed at their own risk.
Always wear safety glasses or a full-face shield (preferred), wear protective clothing, and
work near a source of water to flush any chemicals from your body if needed.
Pour 50 cc of concentrated Nitric Acid into a clean glass beaker. Dissolve a small scrap
of copper in the nitric acid (approx ¼ inch diameter X 0.032 inch thick).
In another clean glass beaker add 250 cc of cold water. Slowly add the nitric acid/copper
solution to the water.
Add 1 teaspoon of Ammonium Persulphate to the water/acid solution and stir with a glass
rod until dissolved.
Clean all oil and grease off the broken tap with solvent followed by Acetone. Allow
acetone to evaporate, then rinse thoroughly with clear water.
If necessary form a dam around the broken tap with modeling clay. Fill the hole with tap
dissolving solution to cover the broken tap. The solution should start bubbling in a few
seconds. It may be necessary to activate the solution by touching the immersed tap with a
clean copper wire and scratching for a few seconds. The tap should be dissolved within 1-
2 hours, and may be etched small enough to remove in less time. Heating the metal part
will speed the rate of removal, but use caution not to reach the boiling point of the liquid.
The remaining solution may be stored in a sealed glass container for a few days, but may
lose its effectiveness if stored for long periods of time.

 

[steamer]

If you go to the front page and do a search of the forum using broken tap + Alum, you'll get multiple hits on the subject.

It would appear to be a saturated solution in water gently heated.....

http://www.homemodelenginemachinist.com/index.php?topic=18332.0

Hope that helps!

Dave

 

[rake60]

I have used the alum trick many times and it has worked every time.

As I have mentioned in another thread, sometimes I just get lazy.
Some of my early models have dummy bolt heads glued over a hole to hide a broken tap.

A few weeks ago I was tapping 6-32 holes to mount an axillary switch on one of the machines
at work. I broke a tap off in the steel machine cover. That's a little tougher to get out but it can be done.
I ground a small piece of a broken carbide endmill to a chisel point and drilled the tap out on the milling machine.

Never throw away a broken carbide endmill!

It's a very simple to make tap drilling tool.

The carbide is harder than carbon steel or tool steel.
Drilling a broken tap out with a home made carbide tool sounds awful!
It grinds, sparks and growls, but it works!

If the tap is broken off in aluminum or brass I'm using the alum.
Breaking one off is steel doesn't mean the part is scrapped.

Rick

 

[Maxine]

Thanks for posting the info all, I will use the alum trick to save my mini V8 block. :bow:

 

[Mosey]

I recently broke a 2-56 forming tap in an aluminum head that has zillions of hours in it. I tried the alum method, following the instructions as I could, and nothing happened after weeks of soaking. It did clean the aluminum to a nice whitish color, though. Maybe I will try again sometime.
I took the head to the neighbor machine shop who milled out the tap with a carbide mill, and then I made an alum plug for the hole, redrilled and tapped the hole. You can barely see the hole if I point it out.

 

[Sshire]

Mosey
On another thread there was a discussion about uses for Marv's new Foredom flex shaft tool.
Foredom makes carbide bits. The smallest is 1/16" diameter. IIRC from tapping the 24 2-56 holes in the radial engine cylinder with a form tap, the hole is larger than 1/16". Since I also broke a form tap in the last hole (why is is always the last hole?) when my birthday present arrives next month, I'm going to order a few carbide bits from Foredom and try "milling" the broken tap out. If it works, there's another item to add to the "what else can I do with the new Foredom" list.
I tried the alum with no luck. Saturated solution made with boiling water.
Maybe I had the Balax "Alum Resistant" form tap.

Best
Stan

 

[Ken I]

If you use the Nitric acid method mentioned avove be very careful not to get Acetone and Nitric acid in contact with each other it gives off copious amounts of brown Nitric Oxide fumes which are hazzardous.

I once accidentally mixed these together while making a Nital etching solution - resulting in the evacuation of the entire factory - I wasn't very popular.

Ken

 

[kvom]

I guess breaking a tap is a rite of passage in the machining world. Welcome to the club.

 

[ninefinger]

I tried the alum method, following the instructions as I could, and nothing happened after weeks of soaking. It did clean the aluminum to a nice whitish color, though. Maybe I will try again sometime.

Mosey,

I had the same experience with just Alum and water. Then I saw somewhere to use vinegar and alum gently heated. That did the trick in an hour or 2. I now have a pot of vinegar and alum tucked away in my shop waiting for my next mistake...

Mike

 

[Mosey]

Hmm...water and alum and acetic acid??? Have to give that a try.
I will also attempt to find out what Balax thinks about this, in the unlikely chance that I will ever break another tap!
Let you know.

 

[Sshire]

Mosey
Let us know what Balax says. They are very helpful on the phone.
I know it's unlikely that you'll break another tap, that's why I have 3 Balax 2-56 form taps

Best
Stan

 

[V 45]

After reading this I didn't see a answer to the mixture except for the nitric acid...what is the mixture for vineger and alum ? How much alum to how much water? I have a #0-80 broken tap at the moment !!! ??? I did another search and found it !! Saturated !! Will try this weekend.

Thanx again...V 45

 

[Mosey]

Balax says that they have never heard of the alum process, and that the only method they know of is EDM.

 

[Jimk 33131]

Jack

Would the alum + water solution work to remove a broken 1/16 drill bit
from an aluminum part ??? ??? ???

 

[Jack]

Evidently the ALUM and water mix works on HSS I am not a chemist nor do I play one on TV. At first I was skeptical but after mixing a little jar of Alum that I got in the spice rack at the grocery store with just enough water to cover my part and heating on a low flame (NOT BOILING, just simmering) for about an hour enough of the tap was gone so that the little piece fell out. I feel confident that had I left it on the stove for another hour or so it would have completely disappeared.
As far as the ratio of ALUM to water is concerned, I don't know the exact formula but I have always been of the opinion that "If a little is good, a lot is better"
As soon as the mixture got good and warm I noticed some little bubbles and some brown funky stuff coming out of the hole might have been some oil, dirt or maybe microscopic pieces of the tap so I knew it was doing something.

As a side note.. this mixture also removed the red DYKEM that I had painted on the part. It came off in a solid sheet of color and was floating on top off the water.

I originally posted this topic because I have heard old wives tales about a lot of things and I was just amazed that it actually worked. My friend the machinist of 30 something years had never heard of it he always has another friend EDM broken taps out.

Jack

 

[Jack B]

Hi Jack: This will not help with the broken tap but should help to keep you from breaking more. The steel block is about 1 by 2 inches. The holes are the size of the tap bodies. This block and a bit of cutting fluid should keep you from breaking taps.

Jack B

 

[Ken I]

Re: Jack's photo in the above post.

Drill your tap size, replace drill with a centre - bring centre to bear in the rear end of the tap holder (that's what the centredrill is there for) - turn tap in with one hand whilst following with the quill - this keeps the tap perfectly aligned.

Ken