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Up Topic Welding Industry / Welding Fundamentals / Broken tap in a blind hole...
- - By yorkiepap (***) Date 08-03-2006 01:52
Removing a broken tap from a blind hole can, at times, become a nightmare. A trick I learned many years ago as a Master Gunsmith, was to use oxy-acet. with an extremely small, high oxy pressure flame. Place the tip of the torch flame directly on the broken tap till it glows bright red and then quickly turn off the acet. and the oxy. will completely disintegrate the tap. It is then just a matter of cleaning out any residual particles left in the hole. I had utilized this method on rifle receivers that were being drilled and tapped for a scope mount and the tap broke in the forward blind holes. This method never jeopardized the integrity of the rifle receiver. Hope this helps someone who may have a similar incident with attempting the removal of a broken tap from a blind hole...Denny
Parent - By webbcity (***) Date 01-23-2008 06:56
Denny , good idea i'll have to try that this year . we always have broken taps working on our families crushers sounds like very good advice . hope to see more from you , and hope all is well with you . good luck . willie
Parent - - By wbic1 Date 05-19-2008 22:20
Hi Denny, I purchased a 66 impala with a broken tap tool inside the crankshaft pulley thread hole.  I wonder if it is a good idea or possible to use your oxy-acet trick to remove the broken tap without damaging the crankshaft threaded end area. I have tried everyting I know how but no avail.  I tried to weld a rod to the short stub which was broke off from the tool and that did not work. I tried to turn the broken staff with a vise crip and that didnot help.  Thanks, Harry
Parent - By DaveBoyer (*****) Date 05-20-2008 04:21
   Harry, there are tools called "tap extractors". These have a fluted shaft with spring steel fingers that fit in the shaft flutes and slide down the tap's flutes. A collar is slid down to contact the workpiece, it keeps the fingers from spreading. I have ocasionally had sucsess  with one of these tools, but about as often, not.

   You could try this method first, You might get luckey.

    With Denny's method it is important that only the tap gets hot, so You should have pretty good acess so You can see what You are doing.
Parent - - By 522029 (***) Date 05-19-2008 22:26
I believe this procedure is with an appropriate size welding tip.  Is this correct?

Sometimes a broken tap or bolt can be removed with an   "air scribe"  or air pencil. 

Griff
Parent - - By Sberry (***) Date 05-20-2008 21:48
Several ways to remove taps.
Attachment: tapwasher.JPG (24k)
Attachment: tapwasher2.JPG (22k)
Parent - By rig welder6 (**) Date 06-07-2008 05:36
u can use a socket (impact) thicker wall, deep or short and weld a beed in the ssocket then use a ratchet to back it out.  i have been very successful on bolts in pump heads that are 2-3" inside make sure to find a socket that fits with out slop grinding of the socket might be needed.  good luck and hope this helps
Parent - - By rlitman (***) Date 07-21-2008 16:09
Well, I finally had occasion to try this trick out this weekend.  I had an iron railing, and I was trying to tap the 1" solid newel for a finial.  Well, I wound up breaking a 1/4-20 tap almost 1/4" under the surface, since the hole in the railing was about 3/8", and the railing was welded to the top of the newel.  This left the tap too deep to grab, or weld something onto.
My first try, I had a relatively neutral flame, and there wasn't much cutting action to speak of.

Second attempt had a strongly oxidizing flame, and once the tap was getting yellow, I shut off the acetylene, and sparks were wildly flying out of the hole.
Within about 3 or 4 seconds, the sparking stopped, there was nothing in the hole glowing, and the tap was completely gone.
In its place, was some cutting slag, around the mouth of the hole.  I ended up drilling and tapping with a larger size (on closer inspection, the finial actually had a 3/8 thread, but had a 1/4-20 insert), but it was clear to me that the original threads could have easily been saved.

All I can say is WOW.  That was cool!
Parent - - By glowingpurple Date 08-05-2008 17:54
Any thoughts to using this procedure on a tap broken off in cast iron?

I got a sander off craigslist - the only issue with it was that the owner had tried to (re-?) tap one of the set screws for the tension adjustment and broke a ~1/4" inch tap off flush the casting. I know cast iron can be touchy about being heated - and it's high carbon. Does anyone see any issues with this, like the casting is more likely to burn first before the tap (no matter how good the heat control is).

Wonderful posting btw.

Thanks,
Mark
Parent - By aevald (*****) Date 08-05-2008 19:49
Hello Mark, welcome to the forum. I believe the basis for this process has to do with bringing the material to it's kindling point and adding the pure oxygen to cause it to burn or oxidize. Since the casting likely has more mass than the broken tap piece, the tap will reach the kindling temperature before the surrounding casting. This should allow it to be oxidized and burned out without causing problems with the parent casting. Best regards, aevald
Parent - - By DaveBoyer (*****) Date 08-06-2008 03:02
   Denny says to use an extremely small flame, that is important. Allan is on the right track about the mass of the casting keeping it from getting hot as quickly.
Parent - - By makeithot (***) Date 08-17-2008 23:53
Dave, Have used those tap extractors myself a number of times also with different degrees of success, they can be some what frustrating. for what they cost you would think they would work alot better but nonethe less they do work.
Parent - By DaveBoyer (*****) Date 08-18-2008 04:30
   If the tap was broken off from side force on the tap wrench they will probably work. If the tap is jammed against the bottom of a blind hole and sections are broken out of the tap down in there deepand locking it from turning the chances are slim. In the tool & die shops We usually had EDM machines and could burn a tap out with them. If I never need to use the torch method that will be OK too.
Parent - - By rlitman (***) Date 08-06-2008 03:18
Well, I used a Victor 00 welding/brazing tip for a 1/4" tap.
I don't think you will get the casting hot enough to be a problem, but if it's small, you could put it in a dish of water.
The post I burned the tap out of, was warm, but not seriously hot, after it was done.
Just remember that the the tap is an incredibly smaller thermal mass, than the casting, and try to keep as much heat on the tap, as possible.
Parent - - By eekpod (****) Date 08-18-2008 12:29
I wonder if this would work with a broken off bolt thats stuck in a hole?

I had an oil pan bolt that the previous owner snapped off when he removed the oil pan on my Mercury 4 cyl engine.  After about a dozen tries I was able to weld a new bolt to the end of the broken bolt, heat up the alum block and back out the bolt, wasn't easy and it took awhile. It was tough but I finally got the broken bolt out, I wonder if this method would have worked easier.
Parent - - By makeithot (***) Date 08-20-2008 01:07
For that I would heat up the bolt with a welding tip not the block let it cool then tack on the new bolt or use that washer tecniqe that was posted awhile back ( It works great.) Let it cool then the bolt will back out alot easier.
Parent - By Sberry (***) Date 09-02-2008 20:37
I often employ a bit of amateur metallurgy especially with bolts, take the twist out of a lock washer so it doesn't snag and weld it on, hardens the connection, then weld a flat over that.
Parent - By BIGWRENCH Date 09-20-2008 05:13
Yes it does, but may kill your cutting tip.
Up Topic Welding Industry / Welding Fundamentals / Broken tap in a blind hole...

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