Broken Bolt Extraction

[ryanbr]

Recently noticed the drawbar support on my tractor had a couple of bolts broken off inside the rear housing. I can not get in there to weld on to them so a extractor is my only option. its a 3/4" bolt so it should be fairly easy to work at, the problem is that its not a clean break, its all jagged and rough which will make it hard to find the center of the bolt. As per the recommendations of my local tool shop I bought something like this http://www.drillspot.com/pimages/75/7514_300.jpg (not the set, just the size i needed which is a bout 3/8 i think), the one bit cost $32!!

Anyone have any tips or suggestions for this kind of thing?

 

[ultrarunner]

Recently noticed the drawbar support on my tractor had a couple of bolts broken off inside the rear housing. I can not get in there to weld on to them so a extractor is my only option. its a 3/4" bolt so it should be fairly easy to work at, the problem is that its not a clean break, its all jagged and rough which will make it hard to find the center of the bolt. As per the recommendations of my local tool shop I bought something like this http://www.drillspot.com/pimages/75/7514_300.jpg (not the set, just the size i needed which is a bout 3/8 i think), the one bit cost $32!!

Anyone have any tips or suggestions for this kind of thing?

I've had good luck removing broken bolts using left-hand drill bits...

If the surface is uneven, I like to use a center drill to establish a hole to start from.

Have not used a drillspot.

 

[tommu56]

Try spinning the with a scribe or some thing sharp I get lucky one once in a while and find one that is loose in there. Or try a center punch and tap it around a little.
I've even cut a slot with a die grinder and used a screw driver.

tom

 

[Scooby074]

First check to see if its loose in the hole

3/4 " so i wouldnt freak about exact centre. Eyeball it and use a GOOD centre punch. Start with a small bit. and work up to the required size for your easyout.

You can buy center punches (called transfer punches) that are the exact size of the hole. This gets you in eht exact centre of what your trying to mark

Another trick is to use a drill of the same size (or close) to the hole your trying to find the centre. You dont drill the whole bolt, but just a couple turns to mark the centre, then follow up with a small drill.
Make sure you dont ruin any threads.

Lastly, there are special (read expensive) welding rods that ill only stick to the broken bolt and not the bore. This allows you to build up the broken bolt so you can weld a nut on at the surface. This would be a absolute last resort.

Good luck.

 

[automech]

I sometimes use a die grinder on a broken bolt to get a nice smooth center spot for my drill to start. You can use a small die grinder bit as sort of a center punch or create a small smooth area to hit with your center punch.

 

[Willl]

welding rods that ill only stick to the broken bolt and not the bore.

How the heck do those work ?

 

[mfreund]

I'll second the left handed drill bits. As a reformed auto mechanic they are the onlt way to go. I have never had any luck with extractor. Bought a set of left handed drill bits and never looked back. I got mine from Mac.

 

[Matt_Jr]

There are several methods I use. One is drilling with a left hand bit. Since it's not smooth, use a cut off wheel or die grinder to smooth it out. Center punch and drill. After drilling use an extractor. Extractors work great as long as the hole drilled in the bolt isn't too big. When it's too big it stretches the bolt into a larger diameter making it more difficult to remove the bolt. I've had luck using sharp chisels with a hammer too. A little heat can be a big friend if safely possible.

 

[Scooby074]

How the heck do those work ?

Some sort of fancy smancy flux that coocoons around the molten metal preventing it from sticking to anything but whats directly under the end of the rod. Lots of flux fills in the exposed threads.

WHen the hole is filled, you have to chip off the flux from the top of the "plug" then you can weld on your nut.

Quote: The Stud Extractor was developed specifi-
cally for the purpose of removing bolts, drills or
taps broken off below the surface of their root.
No special equipment is required for use of this
product. Extractions can be done in the shop or in
the field, anywhere there is access to a welding
machine. This product is coated with a unique
ceramic flux which protects existing threads during
the down hole buildup process. The complex alloy
structure of this electrode allows it to be used on
bolts and taps made of standard or hardened
steels. Its deposited metal is stronger than most bolts
and will even gain toughness as you torque it during
the extraction process.

This is from the stoody catalog. Lawson products have something similar called Cronatron 333. Other companies make them as well. These rods are in the $40 a pound range, but they have a place. If your brave, you can try the same with a 7018. Any rod with lots of flux can work, but the tensile of the speciality rods is much higher.

 

[CurlyDave]

1. Heat is your friend. Heat it to 325 or 350 F and let it cool. I use a temperature crayon from a welding supply shop to know when to stop heating.

2. Use a carbide burr in a Dremel tool to get a short pilot hole started in the bolt. This works especially well if the end of the bolt is uneven and work-hardened.

3. Use a left hand drill to make the hole for the extractor -- sometimes the bolt will come out at this point. I got a set of ~ 8 drills for ~$20

4. Penetrating oil.

5. Use the square extractors, which is what I think is in your picture.