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Thread: Broken tap

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    Default Broken tap

    Have a broken off 1/2-13 tap below the surface of a 'thru' nut. Have a stick and MIG and plasma. I'm working upside down under a loader and would prefer not to set myself on fire. If I aim the plasma torch upwards, I risk hitting hydraulic lines. Somewhere I think I heard you could burn a tap out with a stick welder but am unsure of rod to use and even if this would be best method. Advice surely appreciated...

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    Quote Originally Posted by ColMckee View Post
    Have a broken off 1/2-13 tap below the surface of a 'thru' nut. Have a stick and MIG and plasma. I'm working upside down under a loader and would prefer not to set myself on fire. If I aim the plasma torch upwards, I risk hitting hydraulic lines. Somewhere I think I heard you could burn a tap out with a stick welder but am unsure of rod to use and even if this would be best method. Advice surely appreciated...
    If I had those 3 options I would MIG a 3/8 bolt to the tap. Put the bolt to one side and weld it to the center of the tap. I actually have done it, it does work. Plasma and melting it out with a stick welder is a sure recipe for disaster.

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    Quote Originally Posted by moonlight machine View Post
    If I had those 3 options I would MIG a 3/8 bolt to the tap.
    That was my first thought, but I have little experience welding to High Speed Steel taps. You might weld a deposit on the end of the tap before you weld a bolt to the deposit.

    How deep is the hole, how long is the broken piece, and can you get to the opposite end of it? If you can't weld to it or get to the other end, I think I'd try breaking it up with a sharp pointed punch. Taps are brittle and will crumble small pieces off when you beat on them, resharpening the punch often will help.

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    How thick is the plate or hole,

    If you can get to the opposite side see if you can get music wire or other small wires to slide through so you have spokes.

    Then pliers on both sides and work it out.

    Tap extractors work similar.

    Sent from my SAMSUNG-SGH-I337Z using Tapatalk

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    Default I have saved expensive aircraft parts

    Quote Originally Posted by ColMckee View Post
    Have a broken off 1/2-13 tap below the surface of a 'thru' nut. Have a stick and MIG and plasma. I'm working upside down under a loader and would prefer not to set myself on fire. If I aim the plasma torch upwards, I risk hitting hydraulic lines. Somewhere I think I heard you could burn a tap out with a stick welder but am unsure of rod to use and even if this would be best method. Advice surely appreciated...
    I have saved expensive parts,with a high speed 60,000 rpm pencil grinder.Get about 10 1/8 shank with 1/4x 1/4 grinding points.If the tap is in a 1/2 inch nut ,you only need to go 1/2 deep.You will be grinding with the END OF THE WHEEL IN AN ORBITAL MANNER. I have done this many times. Try to get comfortable and get to it. Edwin Dirnbeck

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    My first attempt at this would be to weld a nut to the tap. Use a nut that's threaded a size or two smaller than the O.D. of the broken tap so you don't accidentally burn out too far and weld the tap to the base metal. Build up the weld on the tap until you hit the nut then fill the nut with a bit of weld too. Use a wrench to back out the tap with the nut. Side benefit is the heat should loosen the tap a bit too. Might be a good idea to fill the crankcase with argon or CO2 first, not sure how flammable the remaining oil might be.

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    Most every welding rod company has an 'ultra chrome' rod that they'll brag on about how they are so strong and useful for welding dissimilar steels together. Use that style of rod, they are good for this purpose and have enough ductility to withstand torquing on a hard joint such as you'd get welding on HSS, bearings, etc. Everyone who has need to do repairs should have these rods in stock, in 1/16 and 3/32" diameters. They produce a heavy flux which flies off spontaneously when the weld has cooled somewhat so be careful to protect your eyes and your neck, as the flying flux is still hot! Don't peen it off prematurely, that precious few seconds under that flux layer helps anneal the heat affected zone just a little, which improves the ductility of the joint.

    I would build up a small dome of weld metal on the center of the tap as a base starting point. Then weld a piece of keystock to it, something you can grab with an adjustable wrench. In an upside down position, the flux deposit isn't going to cooperate when trying to weld inside of a nut, so you'll have to go with many incremental stabs at welding up a good connection. Fortunately, these rods restart very easily. Grind a 45 degree slope on the end of the keystock so you can get in close with the rod, and be laying the deposit in a semi-horizontal mode. You don't have to have the keystock perfectly centered or even vertical. I'd probably use a piece of 3/8 square keystock.

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    I once heard that a tap extractor worked, but don't quote me on this. I'm with moonlight on this.

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    Quote Originally Posted by Ray Behner View Post
    I once heard that a tap extractor worked, but don't quote me on this. I'm with moonlight on this.
    I used them all the time with success....usually on broken taps that were being used to clean out
    an existing hole, so they weren't welded in.

    Other times I had resort to a tap burner, welding nuts on, etc.

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    Right at this moment I have a .150" diameter ~80 grit diamond plated pin cutting a very shallow helix in a 1/4-20 tapped hole in an Al plate. Using a .025" radius, down .0005" per revolution. Hoping to work out the broken carbide that's above the remains of the HSS tap that I was trying to drill with the carbide. Doing a number of short helix passes, with a jump up to flush the hole with coolant every .003" in Z. RPM around 6400.

    If it works I'll report back. If it doesn't I'll be finding a bottle of whiskey somewhere. I don't drink, but I'll make an exception in this case.

    I have done this successfully before, hope my luck is better than earlier today...

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    BTW, I have never, ever been able to break down a "solid" chunk of tap with a punch or chisel. Only times it's worked was when the remains were already fractured from the forces during breakage, if it's an integral lump I drill with carbide (usually works), or resort to diamond when things go TU.

    What really bites my biscuit is I later found some 1/4-20 thread forming taps that I would have used rather than the spiral flute tap I did, if I'd known I had them. Grrr...

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    Quote Originally Posted by Ray Behner View Post
    I once heard that a tap extractor worked, but don't quote me on this. I'm with moonlight on this.
    On that size I've had good success with the Snap-On ones. They have fingers that go down the flute then a girdle thingy that encircles the fingers and keeps them from bending/breaking. On tiny sizes not so much but on 1/2-13, an extractor would be what I tried first. If it works, it's the easiest.

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    Quote Originally Posted by SeaMoss View Post
    On that size I've had good success with the Snap-On ones. They have fingers that go down the flute then a girdle thingy that encircles the fingers and keeps them from bending/breaking. On tiny sizes not so much but on 1/2-13, an extractor would be what I tried first. If it works, it's the easiest.
    That sounds like the Wilton ones. I've had them work but only on taps that broke from a bending stress and not from torsional stress (like in bottoming out in the cut). Best luck I've had with those the extractor didn't work with was to chip away with small diamond tipped grinding tools. Takes patience. If you can get a drill in a solid mount you can grind a start depression and use a carbide drill to get most of the tap out.

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    Quote Originally Posted by rke[pler View Post
    That sounds like the Wilton ones. I've had them work but only on taps that broke from a bending stress and not from torsional stress (like in bottoming out in the cut).
    If you're googling, try Walton. Is the tap 4 flute? The extractor needs to match of course. Fortunately 1/2" gives you fairly large tools to work with.


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    Amazon.com: Walton Tools 181 Tap Extractor Set: Automotive

    I would try these before welding or cutting anything.

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    If a hammer cant fix it, you have an electrical problem.

    only half joking; a punch and a hammer can sometimes back a tap out....or just pulverize bits of the tap.

    best of luck. some good stuff here.

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    Quote Originally Posted by Milland View Post
    Right at this moment I have a .150" diameter ~80 grit diamond plated pin cutting a very shallow helix in a 1/4-20 tapped hole in an Al plate. Using a .025" radius, down .0005" per revolution. Hoping to work out the broken carbide that's above the remains of the HSS tap that I was trying to drill with the carbide. Doing a number of short helix passes, with a jump up to flush the hole with coolant every .003" in Z. RPM around 6400.

    If it works I'll report back. If it doesn't I'll be finding a bottle of whiskey somewhere. I don't drink, but I'll make an exception in this case.

    I have done this successfully before, hope my luck is better than earlier today...
    And to square the circle - diamond pin worked, and there's enough thread left that I chased it with a regular tap and have about a half inch of usable thread. Still a little of the tap at the bottom, but much better than having it stick out of the hole as before.

    I can put the Helicoil toolset away...

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    I'm working on a 1984 model machine; the broken tap could have been 'in there' for 30 years for all I know. Tap extractor is out of the question as it took an half hour and several broken punches just to clean out two of the flutes. The 'nut' with the broken tap is actually a 1" dia piece of (probably) hot or cold rolled about an inch long welded to a piece of 3/8 X 4 bar that forms part of the undercarriage. If I didn't have to remove the hydraulic tank (30 gallon) and 4 hyd lines (a days endeavor) I'd just cut the nut loose and weld a new one in its place. Probably not critical to even have the missing bolt replaced but I kind of like fixing what's broke. With all that being said my final question would still be: can I burn this thing out of there?

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    I have had some luck heating the tap, or broken bolt with torch. Let it get red and hit it with oxygen. Hard on tip, bigger the better. But with what i have that's what i would try.

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    Quote Originally Posted by mkd View Post
    If a hammer cant fix it, you have an electrical problem.

    only half joking; a punch and a hammer can sometimes back a tap out....or just pulverize bits of the tap.

    best of luck. some good stuff here.
    I've found a BIG hammer and substantial punch can shock and shatter the tap so you can take small pieces out gradually. Also a powerful air chisel can have the same effect.

    Quote Originally Posted by true temper View Post
    I have had some luck heating the tap, or broken bolt with torch. Let it get red and hit it with oxygen. Hard on tip, bigger the better. But with what i have that's what i would try.
    ^^^^^^ This^^^^^
    Blow the center out so you can pick what's left of the flutes out of the threads. Needs a big tip so you can do it quickly without making a melted mess.

    FWIW there are portable tap burners who will come to your site, if it's worth that expense. They do the same thing, burn the center out so the flutes can be picked out.


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