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broken tap

Teamfanok

Member
on page 25-05 step 5. Tapping #36 hole with tap 6-32. I broke the tap in the rollbar. What is the best way to remove broken tap. I tried drilling out the tap, but the tap seems to hard for the bit
 
Uh oh

Broken taps are very difficult to remove.
Since the roll bar is not that thick I would suggest using a small punch and driving it on through. The taps will sometimes break into smaller pieces and fall through. The remaining hole might still be able to be tapped for 6/32. Can you go to 8/32 in that location? I'm not familiar with the RV-12.

Mark
 
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A friend showed me a cool gadget last time I broke a tap. Its called a "Tap Extractor". Worked for me. Google it and you will see what they look like - They come in 3 and 4 flute.

Also, I learned there are specific lubricants for thread cutting. Next time I have a few to do I will get recurrent training - Always best to not break it in the first place.
 
Find someone local with an EDM machine. They can burn it right out without harming the surrounding material.

PS. I see you are in NJ. Contact Claudio T. He will be able to help you.
 
I've heard of people using needle nose pliers in the flutes and being able to turn them out.
 
There's a lesson here

There's an important takeaway here:

The 6-32 tap is the weakest one in the standard size range of aircraft hardware. It is the one for which the thread depth is the greatest percentage of the outside diameter. So it is the 6-32 tap that is the most likely to break while tapping a hole, and the 6-32 screw you are most likely to twist the head off of.

I am pretty cavalier when tapping 1/4-28 holes; for rough work I will often go at it with a cordless drill that has a clutch. I am almost as easygoing with the 10-24. With the 8-32 I am kind of careful.

But with the 6-32, especially in expensive parts, I use only fresh sharp taps (none of that Hanson junk from Ace Hardware), good tapping oil, and reversals every quarter-turn to clear the chips. I hold my tongue just so, and think good thoughts with every half-turn of new thread.

Thanks, Bob K.
 
Andy, Bob & Bill give you good advice. I would only use Mark's suggestion as a last resort and ONLY if you used a 4 flute tap. Taps [and tap extractors] come in 2, 3 & 4 flute models. Each has strengths and weaknesses. The 4 flute model centers in the hole the best, will clear the most chip, BUT is the weakest of the 3 styles and breaks the most easily. The 2 flute tap is the strongest, needs to be reversed more often to clear chips, but more care must be taken when starting it. The 3 flute version is a compromise of the other two. My choice for tapping into tough alloys [4130 of the weldment] would be a 2 flute tap.
An EDM machine will definitely be able to remove the broken tap. That said, unless you live in an urban area, you are unlikely to find a shop which owns one [$$$ piece of equipment]. Using a hammer to drive the broken tap through will surely destroy the threads, requiring re-drilling the hole for a #8 screw [considerably stronger than a #6] It may also leave you with a permanent "rattle", if you can not get the broken tap out of the weldment.
Using a tap extractor is something of an art. I would suggest if you can still remove the weldment, that you take it to a god machinist and have him/her remove the broken tap.
Charlie
PS If you own a "made in China" tap set, run, [do not walk] to your garbage can, and insert said tap set inside.
 
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Well

My idea is the most cost effective and the quickest.
The hole would have been repaired last night.

I'll admit I don't even know what this screw is doing, but it is a 6/32.
Please let us know how you fix it and the cost plus your time spent.

Good luck with it.
Mark

35 years industrial maintenance experience.
 
Broken Tap

It is possible to drill out a broken tap with a carbide spade drill. It requires a rigid set up. Shattering the tap with a hammer and punch is done often with mixed results. EDM has the best results but is not economical in most cases.
After you remove the tap and for future holes I would recommend a two flute plug gun tap. The advantage of the gun tap is it pushes the chips forward of the tap requiring no reversal of the tap to break the chip also eliminating the possibility of work hardening the material on reversal. The gun tap is only to be used on thru holes.
My preferred tap brand is OSG they have taps for most materials. My preferred taping fluid for difficult materials, alloy steels and stainless steel is Moly Dee. Only a small amount of Moly Dee is required.
You can also put the tap drill hole in your favor. The 6-32 minor diameter for the 2B and 3B is .104 to .114 . The most common drill used for the 6-23 is the number 36 (.106) diameter but you can use the number 35 drill (.110) diameter making the hole larger requiring less torque on the tap with producing a thread to spec.
We should always check the tap drill hole diameter with a pin gage before tapping and the threads with the appropriate go/ nogo plug gage after tapping.
 
to clarify what the tap was going into, is the roll bar for a RV-12 . This screw holds the rear lexan window. This along with many other screws holds the front edge of the rear window to the rollbar
 
repair

to clarify what the tap was going into, is the roll bar for a RV-12 . This screw holds the rear lexan window. This along with many other screws holds the front edge of the rear window to the rollbar

My apologies Jeff I was thinking of a steel roll bar. For aluminum if a tap extractor does not work I would use a grinding wheel in a Dremel and remove the exposed tap and then tap it out with a punch. The thread will most likely be damaged so I like the suggestion of the nut plate.
For tapping aluminum I would use a two flute gun tap in bright finish.
Aluminum likes to stick to black oxided drill and taps so they are not a good choice. Bolube would be a good cutting oil for aluminum.
Also helpful you can make a simple jig for hand tapping by drilling a hole the od of the tap in a small block of aluminum and use it to guide the tap straight.
 
Broken tap

My commiserations. You seem to have some options to go at.

I managed to snap a tap in the nose gear leg while fitting the wheel fairings. Vans suggested leaving the remains of the tap in the hole and making another hole nearby. In my case, no one can see the error!

Cheers...Keith
 
This is quite an entertaining thread to read.

I'm with Mark, would have had this fixed in under 60 seconds.

Taps are hard and willl shatter when hit with a punch, and would only harm the areas that the threads are engaged in. The hole will still be usable with just a little cleanup.

Last night I was at my buddy's machine shop and was watching a sinker EDM boring a 0.030" starter hole thru a 5" thick piece of Inconel so that the wire of a wire EDM machine could cut the rest of it out. Pretty cool stuff. But a little overkill for getting out a 6/32 tap.
 
?

snipped

Taps are hard and willl shatter when hit with a punch, and would only harm the areas that the threads are engaged in. The hole will still be usable with just a little cleanup.
snipped

Bob,
Considering that the hole is tapped in aluminum, just how do you expect any of the female threads to still be "repairable" after driving a hardened steel tap through it? Those threads would be totally wiped out. I'm unfamiliar with how thick this roll over bar is, on the 12. Providing that it was at least 1/8" thick [approx. 1 diameter of the #6 screw], the ruined threads could simply be repaired using a #6-32 HeliCoil insert. Thinner than 1/8" would require re-tapping to #8 or installing a nut plate as was mentioned earlier [providing there is access to install one] If the roll over bar is made from 6061, you might consider simply welding the mangled hole shut, for a "do over".
Am I missing something? I've broken off my share to taps and gotten them out. I would consider trying to shatter one, if it was lodged in 1/4" [or thicker] steel, but not in aluminum.
 
It it didn't shatter (which they do, even in aluminum) then since its likely a two flute tap at least 50% of the threads remain which would hold a screw just fine, especially considering the light load of the canopy glass.
 
I have been a machinist for over 25 years and would indeed try to use a tap extractor first. But it must be done very carefully. I own and have used several
times a Hansvedt EDM or Spark Eroder. They are absolutely the best way to
remove broken taps as they do not damage the treads. Good luck.

Andy Jones
 
I had to have a broken tap removed from a motorcycle cylinder head a couple of years ago. The EDM worked very well. After that experience, I wouldn't even mess with trying to remove it myself. Now, I would just take it to a machine shop that has an EDM.
 
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