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