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Old 16-01-2009, 14:42   #1
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Angry How Do You Remove a Broken Tap?

The fellows working on my boat today broke a tap in the stainless part they were tapping. The tap broke flush with the stainless so there is nothing to grab to remove the broken piece. Anyone have any ideas? Thanks

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Old 16-01-2009, 14:54   #2
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Drill the centre of the tap and use a screw extractor.

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Old 16-01-2009, 14:59   #3
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Might have to use a cobalt bit on the broken bit. Tough stuff.
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Old 16-01-2009, 15:02   #4
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What he said, center drill and extractor (easy out).

If that doesn't work, drill out the entire tap.


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Old 16-01-2009, 15:07   #5
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You might be able to back it out enough to get a grip on it using a small chisel. Just tap on the edge of the tap very lightly. You didn't mention the size but larger sizes are easier to get turning. Have used this method with broken bolts. Go easy and don't try to rush it and it might work. Good luck.
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Old 16-01-2009, 15:21   #6
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If you are lucky and the tap has broken but not through seizing so it can still be relatively easily turned but just need a grip on it you can beg/borrow or steal a tap extractor which puts a couple of arms down into the flutes of the tap to get a grip. If the tap is quite loose you may be able to get a grip with a good pair of pointed nose pliers down into the flutes. Grinding a screw driver slot in the top with the likes of a Dremel tool might also work if accessible.

If it seized tight then you have two ways that I know of and both are pretty much guaranteed to work.

You can take the item to a workshop that has a tap/bolt disintegrator - these will disintegrate the tap electrically. They usually aren't portable as far as I know.

Or you can TIG weld a nut onto the top of the remains of the tap filling the hole in the nut with weld metal and then use the nut to turn the tap. This will work even if the top of the tap is below the surface as the TIG welding only works in line with the electrode so one can fill the hole above the tap with weld metal without it adhering to the sides of the tapped hole and then when the hole is filled weld the nut on as above.

For low value items it may be cheaper to start again.

EDIT: I'd be very surprised if you find that you can drill a quality tap and think you will find it will cause more problems trying than it is worth.
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Old 16-01-2009, 15:50   #7
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MidLandOne has the best idea. The tap extractor was my first thought.
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Old 16-01-2009, 16:15   #8
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I have never had luck drilling them. Sometemes you can get them freed by tapping and work them/pick them out.Otherwise Midland is right on
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Old 16-01-2009, 16:43   #9
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Hi Gbanker. Bummer! Limited options are 1) EDM (electrical discharge machining); 2)if you can swing the part in an engine lathe it can be clamped to a faceplate or chucked in a four-jaw and ground with the tool post grinder (Dumore or equivilant); 3) if you can find a tool & die shop with a jig grinder (Moore or equivilant) you might find a machinist to set it up and grind the tap out that way. Replacing the part would be my first option, cost considered. I cannot imagine anyone tapping stainless with carbon steel so that tap is probably high speed steel which is really going to get ugly if you touch it with anything including carbide. Sometimes (not very often) if you use a left-handed drill, the drill point will catch a flute and spin the tap back out. Please, please wear safety glasses if you try this [unadvisable] tactic. Tap extractors are a crap shoot (it would be helpful to know what size you're talking about). ps, you gotta nice boat!
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Old 16-01-2009, 16:54   #10
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Most shops that I have worked with will use an edm machine to cut it out. They can burn a hole through it and cut it out with wire on an edm machine. I sell the taps used in production machining and that is the most common way we see taps removed. Most often when a tap breaks it is because either it hit the bottom of the hole or the chips got caugt in the teeth. Either way, if this is what happened, the threads are likely to have been distorted and the tap will not back out easy. Drilling it out is not likely to occur unless you use a carbide drill. This would require a very ridgid set up as carbide is hard but brittle and does not like to flex. Thus the reason they use wire edm.

Good luck!

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Old 19-01-2009, 19:36   #11
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Hey gbanker, did you ever get that tap out?
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Old 19-01-2009, 20:06   #12
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Last time I broke off a tap it was in stainless. We got it out by dissolving the tap in sulfuric acid (or was it muriatic?). Anyway, if you can physically move the piece, acid will work with no damage whatsoever to the stainless.
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Old 19-01-2009, 21:52   #13
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yer kinda screwed ,you cant drill out a tap . you can make an extractor though,take a junk screwdriver and cut the end like a fork then shape it till the tangs go into the slots in the tap,lookin from the top the tap looks like a cross.use the tangs youve made to engage the tap,lube it down with spray wd whatever.heres the patient you gotta kinda rock it back and forthit will eventually work loose,,,if not you can throw caution to the wind and break it with a chisel,taps are verry hard and you can shatter them and pick out the pieces,,,,pe shure and slap the beejeezus out of the moron who broke off the tap,,ive done that to many,many helpers over the years and they still mess it up but it makes ya feel better..ha ha...happy boating
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Old 19-01-2009, 23:17   #14
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I've never had any luck drilling a tap. Tried cobalt, carbide, and hss on a drill press with the piece clamped. Barely scratched it. You might be able to use a dremel heavy duty cut off wheel to grind a screwdriver slot in the tap. Good luck!

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Old 19-01-2009, 23:32   #15
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Ok...This is from a Toolmaker...Some of the suggestions above are good. The ones about drilling out a tap are jokes. Tap have a very high hardness to them. No use throwing out the number, it won't mean anything. There are 2 reasons for a tap to break..1) you hit bottom, it jammed and snapped. Or 2) you put side load on the tap and as we know...taps don't bend. A tap remover as described by MidLandOne would be your first option. Then option #2 is a liquid tap remover, available at a machine shop supply store. I assume we are talking about a blind hole. You build a small dam of Plasticine around the hole and pour a enough tap remover to fill to the top. About once an hour you will need to refill. This can go on for days. Option #3 is taking the part to a machine shop with an EDM (electro-discharge machine) and burn it out. Option #4 is to use a carbide spade drill and drill it out using a milling machine. Option #5 Buy a new part

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