Busted tap question

I broke a tap today. There was not enough protruding for me to get a grip and twist it out. I thought I would anneal the tap in situ and drill it out. So I heated it red hot with my TIG torch and let it air cool.

When I tried to drill, I found it was still way hard and I abandoned the idea of drilling out the broken tap. I had the flexability to drill and tap beside the original hole so there was really no great loss. But, what if I really needed that particular spot?

Would I have had better luck drilling had I cooled the part more slowly (e.g., buried the part in a bucket of ash)?

Is my thinking nuts or is this a way to get at an offending broken tap?

TIA, David Todtman

Reply to
David Todtman
Loading thread data ...


There are several options.

Grind it out with a Dremel tool and grinding tip.

Drill from the other side and beat the tap out with a punch.

Break up the tap with a punch. Fish out the pieces.

Do as you did and drill a larger hole next to it and break out the tap. Then drill a yet bigger hole and fill it with a stud. Grind smooth. Drill and tap again.

Bob AZ

Reply to
Bob AZ

Unlike carbon steel, HSS requires a long soak time (hours) at approximately

1500 F, then very slow cooling in order to anneal. It is often permitted to cool down with the furnace to avoid air quenching. Heating with your TIG torch and then allowing it to cool as you did is highly unlikely to have had a softening effect on it. HSS can be successfully silver soldered or TIG brazed with silicon bronze rod to shanks with no negative effects, which makes it possible to make custom tools for those rare occasions when you can't otherwise machine an object. .

Aside from the tips you've already received, you could always EDM the center out of the broken tap. Years ago, long before EDM's were on the market as we know them, Elox sold a tap burner that used tubing as an electrode, and that was the prescribed procedure. Burn the center out of the tap, then pick the teeth out of the existing threads. Working carefully, most broken taps could be removed successfully. As I recall, it required a little skill on the part of the operator to avoid burning the threads.


Reply to
Harold and Susan Vordos

What was it in? If it was steel, your only choices are EDM or (maybe) a solid carbide drill or end mill. If it was in aluminum, you can disolve it out with nitric acid.


Reply to
Jerry Foster

I have been able to remove a few by welding a nut to the broken tap. Fluxcore mig worked for me.

(top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

Reply to

Since you've got the TIG. weld a nut to the stub of the tap. Depending on the tap's size and how much is sticking out, it may be helpful to countersink the nut in order to reach the end of the tap. If the tap is broken below the surface or the stub is very short you can build the end up with weld before laying the nut over it.

309 SS wire will work well, but 308 or 316 is OK, Inconel or other high nickel rod is probably best. If you've got some, old fashioned trichlor based tapping fluid will make it much easier to get the tap moving.

Ned Simmons

Reply to
Ned Simmons

There are tap extractors available, but if you don't have one, just find a piece of tubing the same size and cut 4 slots into the end so the remaining

Reply to

Lots of good ideas.

I've found tap extractors usually don't hold up very well. When we break a tap, the first thing we do is head for the dull carbide bin. If you are careful, you usually can cut them out with a solid carbide endmill. On a very rigid milling machine. The tap is going to break into pieces, and those pieces are going to chip and ruin your carbide, so we keep some dull ones around just for this kind of problem. Carbide is very resistant to heat, so when the cutting edges are nearly gone, crank up the RPM and apply some pressure. Resist the urge to use coolant. When the tap starts to glow (and maybe the carbide too), it will also start to cut. If you're not the type to wear safety glasses, better start now! Something WILL break. This almost always works if the tap is large enough to use and endmill. If not, we go to the EDM.

BTW, the corners just break off of a flat bottom. We usually try to use a ball endmill.

Reply to
Dave Lyon

The way you can attack a broken tap depends on several factors.

What size was the tap?

Is it a blind hole or a through hole?

How many flutes on the tap?

Did you drill the recomended size hole or were you trying to cheat with just a little smaller diameter drill bit?

What kind of metal were you trying to tap?

Reply to
Roger Shoaf

Thank you all. Very helpful and informative.

David Todtman

Reply to
David Todtman

You are almost there with your tig. Sharpen the tungsten to a perfect point, then start with low heat and carefully liquify the tap holding the electrode in the center of the tap. I keep increasing amperage slowly until almost the entire tap is melted. Then with stainless rod, add filler slowly until you have a ball built up on the tap. While it is still hot grab the ball with vise grips and gently work in both directions to loosen, then screw it out. This works about 50% of the time or more. I have been brought expensive parts to remove taps with an edm and almost always try this first. Some customers will come back the next day for their "edm" job, when in reality I have the tap out before they are out of the parking lot! And of course I don't charge them for the much more expensive edming.(grin). Dixon

Reply to

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.