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Broke off tap. Need help!

Kevin Weis

Subscriber
Last Subscription Date
01/13/2019
All, broke off a tap in threaded hole on my 1 hp Famous. What's the best drill bit to use to attempt to drill it out? Thinking a diamond tip bit would be best. Any thoughts appreciated. Size is about 3/64" - 1/8".
 

TekNik

Registered
A few Questions:
What size tap is it?
How deep in the hole is it broken off?
Is there part of the tap above the surface?
Is the fracture parallel to the surface?
TekNik
 

Paul Richardson

Subscriber
Last Subscription Date
01/05/2020
All, broke off a tap in threaded hole on my 1 hp Famous. What's the best drill bit to use to attempt to drill it out? Thinking a diamond tip bit would be best. Any thoughts appreciated. Size is about 3/64" - 1/8".
Not really sure why you would need a special type drill Kevin? Am I right to think the material will be either brass or mild steel?
My favourite method with bolts and studs is to make them look like a broken off tap spigot in the hole by drilling the center out as near to the thread as I can get.
After that I insert a small hand held hacksaw blade saw.Sometimes I need to reduce the height of the blade on the bench grinder to allow it to fit the hole.
I section the remains of the bolt or tap,in two three or sometimes four sections,taking best possible care to saw TO the thread and not through it.
I then use a small hammer and punch perhaps like a broken then resharpened scriber and very gently punch from the edge inwards to break out the first willing section.Minor damage to the host thread can usually be renovated ok with a tap.
Don't rush,be gentle,and sometimes a plumbers torch is a great help.I get great results when the job allows that method.
 

ssimntih

Subscriber
Age
34
Last Subscription Date
12/18/2019
I usually use carbide end mill, if you have the luxury of owning a mill. You definitely need something harder than the tap.
 

Tom Cwach

Subscriber
Age
62
Last Subscription Date
10/18/2019
find a machine shop with a wire edm would be best.

I have had some success with breaking them up with a punch but you're working in a small hole.

Most taps will evaporate if a cutting torch is used on the larger ones.
 

pegasuspinto

Registered
Years ago my boss took one out of a delicate spot with a handfull of carbide burrs in a dremel tool, with a steady hand. they had already busted a tap extractor. In the end of a crankshaft. Cleaned it up, put in a new bolt, and worked fine.
 

Dale Barnett

Registered
Last Subscription Date
09/24/2013
That small you won't remove by drilling with out a good mill as you won't be able to hold perfect center and good luck finding a carbide or diamond drill that small.
We never heard if it broke off flush down in and if so how far.
I have had good luck if it is flush by mig welding a nut on it.
 

Elden DuRand

In Memory Of
Age
78
Last Subscription Date
12/22/2017
Okay, here's my method that works sometimes if all else fails.

Pounding lightly using a piece of soft steel as a punch (so as not to shatter the tap), try to loosen it a little. Then with either a forked tap extractor or a small punch, try to rotate it a little either way. If you're lucky, you can get it to move. Keep the hole cleaned out with air and coax it out. A lot of patience helps.

Been there - done that.:rant:
 

Nick

Registered
Last Subscription Date
04/18/2014
Forget all that stuff about drilling and tap extractors. With a tap that small you have 2 choices. First would be to find a shop with a tap burner. Second is to find someone with a milling machine who knows what they are doing. A good machinist and a carbide end mill will get that tap out. May need a thread insert installed if breaking the tap damaged the hole but at this point your part is salvageable.
 

Paul Richardson

Subscriber
Last Subscription Date
01/05/2020
Okay, here's my method that works sometimes if all else fails.

Pounding lightly using a piece of soft steel as a punch (so as not to shatter the tap), try to loosen it a little. Then with either a forked tap extractor or a small punch, try to rotate it a little either way. If you're lucky, you can get it to move. Keep the hole cleaned out with air and coax it out. A lot of patience helps.

Been there - done that.:rant:
Duh?..i mistook the question to be about a valve type tap!:bonk:
What Elden is describing here with a thread tap I have heard only once before when it was explained to me by a very experienced old engineer,and old iron enthusiast.I think that would be my approach also.
 

slugga

Registered
G'day Kevin, I've been a Toolmaker for 30 years and have broken more than my fair share of taps, I can tell you from experience that no high speed steel drill bit will even look at tungsten carbide doesn't like intermittent cutting it will just break and chip, trying to soften it requires heating it red hot and cooling it very slowly like overnight slow this can be done by packing in lime, possibly a bit impractical but not impossible then grind out with a carbide burr on a dremil or die grinder, or if the part isn't to big take it to your local engineering shop and have it spark eroded, this is possibly your best option, however there is one other option that I personally have never tryed but know blokes who have, and that is a stellite drill bit this works by extreme localized heating and melting it out, l really don't know much about them so some research may be in order, or just try the extractors that was spoken about earlier, have never used them but they look like they would work, and you will always have it for another broken tap. I hope there was some help here. Regards. Neil.
 

Tanner Remillard

Subscriber
Age
36
Last Subscription Date
02/05/2020
Take it to a machine shop and let them deal with it. All machinists have had their fare share of taps broken off. I hate it when people break off a tap or a bolt, then try to remove it themselves and brake off whatever P.O.S tool they tried to use to get it out, then that just makes it harder on us. 95% of the time I just use a carbide end mill in the Bridgeport, and you have to be damn careful when doing it. Like said, trying to drill it out is just going to blow up the drill. If a shop has a metal disintegrator that's the best. We have a big one at work for removing larger bolts. Can burn a 1/2" square hole in larger broken off bolts then stick a 1/2" drive ratchet in it and back them out.
 

beezerbill

Subscriber
Last Subscription Date
01/10/2019
First thing is to see if it will back out using a needle nose pliers. If it is jammed in this probably won't work but if it broke because it was bent sideways you might find the stub left in the hole is fairly loose. You could also try LIGHTLY tapping on it with a small punch to see if it loosens up. I have also removed broken taps with a Dremel tool with a grinder bit - which is real slow but controllable.

Drilling it is not really a good idea. First, you need something like a milling machine or real rigid drill press. You will need to perfectly center the tap under the spindle. Then a carbide spotting drill is used to put a center divot in the end of the tap. and if the end of the tap is broken off crooked (they usually are) this step is especially hard. Sometimes the end of the tap needs to be faced flat before the spotting drill is used. The reason for the spotting drill is that it is especially stiff and short and unlikely to wander. The spotting drill is followed by a stubby carbide spade or straight-flute bit. These bits need to be the right tip geometry and carbide - your garden variety carbide twist drill will just shatter.

The preferred method is to find someone with an EDM "tap burner."

Let us know how it works out!
 

OldAgIron

Registered
Last Subscription Date
01/13/2016
As a tool and die maker, I would agree, if you don't know what you are doing , leave it alone, it will cost more in the long run. Tap burners do a awesome job, if you can find somebody with one. or get it on the mill with a carbide endmill. I know all that sounds pricey, but in the long run you will be money ahead.
 

John Kendrick

Subscriber
Last Subscription Date
11/26/2019
I have had success heating the end of the tap with a very small oxy-acetylene welding tip until it is red hot, then turning up the oxygen. It is in effect a controlled burn. The threads aren't hot enough to burn, if you take it easy.
You can learn lots of desperate tricks on a ranch seventy miles from town.
But---I would practice this on an old drillbit in some scrap, first.
Old Cowman
 

Matthew Guy Clarke

Subscriber
Last Subscription Date
09/23/2019
Kevin, I was wondering where the hole the tap is at.
Do try the broken tap extractor first. If you want to drill out a tap, it is not easy and may be impossible. You may be able to blow it out with a cutting torch. The first thing you need to do is determine if it is high carbon steel or high speed steel. To do this, look at the remaining broken half. It is silver shine'y it is high speed steel, the only remedy other than broken tap extractor I know of is to burn it out with a hot carbon rod,which is what was described in earlier advisement to take to large shop, and have burned out. The carbide burr could work too, or mill ?
I had one broken off on the side of a steam cylinder once, I ground out the whole area, and knocked the tap out, welded up the area and machined flat again,not easy,but fun.
I could burn it out with the carbon rod, you use a carbon rod, and electric apparatus, with hand feed down screw, I am not wanting the job, take it to the shop.
If the tap has black look, it may be high carbon steel, heat it red to orange hot, and see if it anneals, by striking with a file.If it files it will then be high carbon steel, one could blow it out with an oxy acetylene torch (with a small tip for such a small screw, it must be in the head where the retard advance bracket sets?
If you could heat the thread part of the tap,(whole head)? if it is high carbon steel, you could Anneal and drill it out. It takes one week at about 1,720 to anneal highspeed steel. It also can not be blown out with a torch. High speed steel will not cut with a cutting torch.
When tapping on valuable or difficult iron, I always buy and use a new high carbon tap, in case I need to blow it out with a torch.
 
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