broken tap

[T.L.A.R. eng]

I have just broken a recently new 2-56 tap off in a 3/8 inch deep hole in 7075 aluminum. Has any one ever made a hollow hole saw to try and render out the offending tap piece? I thought of trying drill rod to make the cutter then harden it. Kind of like a small hole saw, then tap the hole for a plug of metal and re-do the 2-56 threads. I don't have a lot to work with except time. Any thoughts?

[ezdoesit]

If you have some time you could make a edm from the home shop machinist lay had a book you could buy. I have one i made, it will do just fine.

[widgitmaster]

If you have a bridgeport or knee type mill, simply use a small diameter solid carbide endmill to drill the broken tap loose!
Do this by first getting on the exact location, then rais the knee very slowly to let the carbide take light cuts on the hardened tap metal! You may need two or three carbide endmills, but the tap should come out!

If you can do this from the opposite side, the tap may just un screw too!

[T.L.A.R. eng]

I cannot reach the back side of the hole as it is a blind hole. I would love to build the edm, just didn't want to use it for this. If I use the edm, what happens when the tap material is gone? Are there threads left?
I know the tap was jammed at the bottom of the hole as I heard the tap "tink" then it was jammed and would not retract. It seemed to come loose, then without any resistance, broke off flush.
I seldom ever have any problems with hand taps but you know how it goes with the importance and care given to the project, things seem to happen expotentially. I will try the carbide end mill first, Thanks guys.

[One of Many]

Since this is Aluminum. Do a search for Acid and Broken Taps here or on the web. Nitric acid, sulfuric or hydrocloric can disolve the tap without doing harm to nonferrous base metals. It would be a good idea to test the acid effects on the aluminum, but the right mixture/recipe should do the trick.

DC

[dertsap]

for such a small tap size i would suggest sending it out for edm which will be cheap to have done ,i like to burn out taps with old carb endmills but with that dia. of a tap , 1/16 is all you going to get in there and to burn 3/8 of an inch you would be sol , too high of a chance of destoying the threaded hole

[ViperTX]

Guess you need to decide if it's worth it before you do anything....2-56....pretty small.....most anything that you attempt to drill it with will most likely break unless the broken surface is pretty flat......

[Beaker]

I know the feeling, ya spend heaps of time on a job and then it all goes down hill in a second.
Only recently I had to remove a broken tap from a piece of 6061. It was an M2.5 tap about 10 deep and luckily I had a 2mm carbide cutter, just milled it out no probs. Cleaning out some of the remaning tap did pose a few dramas but in the end it all worked out.
Hope you get it out
Good luck

[T.L.A.R. eng]

Thanks to all for the advice, I appreciate the wealth of knowledge on this site. Gary

[snakebit95]

If it is critical to saving the part, look for a local die shop. Give them a call and see if they have a tap-burner. We have one in our shop that we use to save large castings when we break taps off during machining. It gets very expensive when you have to scrap a $300 casting that has a couple hours of machining already invested in it due to a small broken tap in a hole. Hope this helps!!

[Mcgyver]

like One says, or use Alum....

http://bbs.homeshopmachinist.net/sho...ium+broken+tap

http://bbs.homeshopmachinist.net/sho...ium+broken+tap

[ezdoesit]

thank you all. I just found a lot of thing i forgot i had read befor.
They said if you don't ues it you forget it