Snapped Screw Extractor

Was removing front diff skid plate preparing to change the diff oil and of course one of the 4 bolts snapped. It actually started backing out but then added resistance and broke off. No biggey. I punched a dimple and started drilling with progressively larger bits to insert the extractor. Started with a fairly small one but quickly decided to move up 2 sizes. Drilled some more, pounded it in and started twisting. All the while during the drilling, I kept squirting wd40 and tapped the stub with a hammer. When I got the wrench on it I did not horse it, just kept applying increasing pressure. I heard a slight gritty sound so thought great, it's starting to twist and it was. Unfortunately it was the extractor and not the stub.
Im thinking now I need to find a reverse cut extra hard drill bit to drill out the ext.
Any other suggestions?

 

Left hand threaded bits work well for this, sometimes you get the bolt to spin out while drilling it.

I have

$40 Irwin Tools IRWIN Screw Extractor/Drill Bit Set, 10-Piece (11119)

this kit and had to use it for a skid plate bolt, it came right out.

 

what sort of tools do you have access to? think it's corrosion or a messed up thread? if it's corrosion, easy enough to get out with something like PB Blaster. If I'm reading this correctly, there is a bit of thread exposed?

 

I don't think there are drill bits for broken extractors. They're too hard. If the extractor broke off in the hole you're screwed. You might be able to get it to break by hitting with a hammer and chisel if you're lucky. There's a place that specializes in getting them out in California, so if you're local to them maybe they could get to the frame. Here's a link if anyone here ever needs a broken tap or extractor removed. The vid on some of their work was interesting; http://www.brokentap.com/index.html?gclid=COeU4Mz7oacCFQjd4AodYWu2wA

 

You can drill out the extractor with a straight flute carbide drill bit. You need to be very careful to not let the bit jam or it will crack due to how hard it is. They also expensive. Toy4me is also correct in saying you may get lucky and crack the extractor out with a chisel or punch. I do this a lot where I work it can be a PITA, but not impossible.

 

Oxy/acc torch. Heat directly on the extractor. When it a dull cherry red, back the torch off some but keep it pointed at the extractor for a good minute, then let it cool. This will take the temper out of the extractor, and probably loosen up the broken bolt as well. Then go at it with a wrong'handed drill bit.

Make damned sure you don't heat anything you don't want heated, like the rest of your truck.

 

Thanks for all the FB. There is very little of the stub standing proud so nothing there to grab externally. I did find where I could buy a near $50 bit that is hard enough to chip away but it is also subject the fracture. I don't own oyx/acc torch.
How's this for a simple solution.
The broken stub is the back right corner. There's room on the plate flange for a new hole. I'm thinking of simply drilling a new hole in the plate and frame and ignoring the broken stub.
I know....sort of a cop out....but considering what and where it is....