Tools/techniques/tips for extracting a broken tap?

[cnczoner]

In 6061-T6 btw. Is there a regular tool for this?
Thanks,
-Neil.

[HuFlungDung]

Drill out the core of the tap with a carbide drill....not a twist drill but a heavy duty spade type drill point. Personally, I reserve old worn carbide endmills and burrs for this kind of 'last legs' service It is a practical necessity to have a diamond grinding wheel to frequently reshape or touch up the edges.

[big_mak]

it all depends on how much time you've put into it, and how much the material is worth, before i even consider taking it out. sometimes it's just cheaper to scrap the part.

[HuFlungDung]

I like to practice on things that aren't important so I have a half a clue what to do when I get a job that really needs the tap taken out

[big_mak]

That's fine and good if you are between production runs, but man we're here to make $$$$$$$$$$ LOL

I know I get caught up in that stuff too!!!!! Just wait until those guitars take off Hu, THen I can tinker all day!!!!!!

[Geof]

Originally Posted by HuFlungDung I like to practice on things that aren't important so I have a half a clue what to do when I get a job that really needs the tap taken out

Only half? I thought you aspired to better than than.

I have successfuly, and quickly, removed broken taps from aluminum by welding a nub on the end with a stick welder and stainles steel electrode. Just enough to grip with ViseGrips. The heat tends to loosen the tap which helps start it turning.

This also works on brass and to a lesser extent cast iron but on steel you have a better than 50% chance that you will finish up welding the tap to the job.

[DJPLAST]

Just burn the center core of the tap out with a copper tube in the handy dandy EDM.

[cnczoner]

In this case, it's not that important, and I really didn't need that tapped hole (since I overkilled the number of holes), so I ground down the stub of the tap with a dremel and ignored it. I want to know for the next time I mess this up. :-) This was 8-32 btw.

I'm very new to all this machining stuff so I expect there will be other times and scrapping or salvaging will depend on how much time/money I have invested in a given part. I am really mostly using endmills of 3/8" and 1/2" dia, so I'll have to get some others and experiment with some drill bits.

Thanks,
-Neil.

[cnczoner]

EDM? Fat chance for me, cause my machine shop is a 5' x 5' corner of a single car garage. :-)

[widgitmaster]

Originally Posted by cnczoner EDM? Fat chance for me, cause my machine shop is a 5' x 5' corner of a single car garage. :-)

Sounds like my shop!
If I break a tap, and need to remove it, I take a 4 flute carbide end mill just a tad bigger than the tap's web. Then I hold the end mill short and rigid, and lock the quill. Then i raise up the knee slowly to remove a portion at a time. while cleaning out the hard chips with air, as they will crumble the carbide if not removed.

When through the tap, I carefully pick out the remaining tap pieces and use a needle type air nozzle to get to the bottom of the hole.

It is time consuming, and it may take a few end mills, but sometimes a part can have a lot of time in them and that makes them valuable!

By the way, an 8-32 tap is proportionally one of the weakest taps and very easy to break, especially in soft aluminum!

Hope this helps,

Widgit

[Geof]

If you don't have fancy EDMs, or stick welders and stainless electrodes, or carbide spade drills, but are working with a CNC machine all is not always lost.

Interpolate around the broken tap, close but not too close, maybe 0.01" away from the tap OD. Go down deep enough that you can break off the little cylinder of metal that the broken tap is in and extract it from the hole. The reason you don't want to be too close is you don't want it breaking off prematurely and smunching the cutter.

Then open the hole up to a standard tapping size, tap an oversize thread and screw in a plug. I have done this a few times when making tooling for use in-house; but don't ever do it for a customer's job

[cnczoner]

Originally Posted by widgitmaster By the way, an 8-32 tap is proportionally one of the weakest taps and very easy to break, especially in soft aluminum!

Really. Interesting info. So from 4-40 to 10-32, which is considered the strongest? My most popular size is 6-32.

Originally Posted by Geof ...Then open the hole up to a standard tapping size, tap an oversize thread and screw in a plug.

Hmmm... hadn't thought of salvaging the hole this way, but I like it!

Cheers,
-Neil.