Extracting broken drill bits - my method.

[alchemysa]

Yesterday I broke a drill bit inside a broken bolt that I was trying to drill out. No way could I get a grip on the broken drill bit so I used a method I have used in the past with success. I simply smashed the stuck drill bit to pieces with a home made punch. I googled to see if anyone else had tried this but didnt find it mentioned anywhere so I'm throwing it in here for comment.

The idea of bashing a broken drill bit even deeper into the hole seems completely counter intuitive but it has worked well for me. Drill bit metal is brittle so it breaks into small pieces quite easily. You just need to make a suitable punch that fits the hole LOOSELY. An old hard bolt, and the shank of a broken drill bit, have both worked for me. Hammering on the punch creates broken pieces that can be blown, vacuumed or tipped out as you go. You may think you are going to eventually get a hard packed wad of powdery pieces in the bottom of the hole but in fact that isn't a problem. Any wad that develops is easily broken up with a pointed tool such as a small screwdriver.

Anyone else used this method?

One other tip if you are trying to drill out a bolt. Never go deep with fine drill bits. A pilot hole should be just deep enough to give a larger bit a starting point, If you can't drill down solely with a large bit, and need to use a variety of drill sizes, work down the the hole in stages, widening the hole every few mm, so that you never have a fine bit deep in a hole where it can bind and snap. Obviously in the event that a bit does snap, and you need to use the method described above, you want to be working in the widest hole possible. Also use oil so you reduce the chances of bits binding and snapping.

Comments to correct any bad advice I might be spreading here are welcome.

(Edit, The tip snapped off another drill bit today and I basically used the same method again with success).

 

[dickfoster]

Yesterday I broke a drill bit inside a broken bolt that I was trying to drill out. No way could I get a grip on the broken drill bit so I used a method I have used in the past with success. I simply smashed the stuck bit to pieces with a home made punch. I googled this idea but didnt find it mentioned anywhere so I'm throwing it in here for comment.

The idea of bashing a broken drill bit even deeper into the hole seems completely counter intuitive but it has worked well for me. Drill bit metal is brittle so it breaks into small pieces quite easily. You just need to make a suitable punch that fits the hole LOOSELY. An old hard bolt, and the shank of a broken drill bit, have both worked for me. Bashing away on the punch creates broken pieces that can be blown, vacuumed or tipped out as you go. You may think you are going to eventually get a hard packed wad of powdery pieces in the bottom of the hole but in fact that isn't a problem. Any wad that develops is easily broken up with a pointed tool such as a small screwdriver.

Anyone else used this method?

One other tip if you are trying to drill out a bolt. Never go deep with fine drill bits. A pilot hole should be just deep enough to give a larger bit a starting point, If you can't drill down solely with a large bit, and need to use a variety of drill sizes, work down the the hole in stages, widening the hole every few mm, so that you never have a fine bit deep in a hole where it can bind and snap. Obviously in the event that a bit does snap, and you need to use the method described above, you want to be working in the widest hole possible. Also use oil so you reduce the chances of bits binding and snapping.

Comments to correct any bad advice I might be spreading here are welcome.

Never tried that one but I'll log it away for future use.
If the bolt is at least flush with the surface you can try my method. Lay a nut over the end of the broken bolt. The nut has to be smaller than the bolt so you don't weld the nut to the surrounding metal. Then weld down though the nut welding the end of the bolt to the nut. Put a wrench on the nut and back the bolt right out. The heat from welding also helps loosen up frozen bolts as it was likely frozen to begin with and that's why it broke off.

 

[Industrial Toys]

How big a bolt are we talking? That would make a big difference on ones strategy. I know a guy that has reverse drill bits. What a luxury.

Love the welded nut idea. With my eyesight and welding skills I'd turn everything into one ruined blob!

I used to have this 16 foot finishing mower with 1/2" reverse thread blade bolts. Hit a groundhog hole or ant hill and the bolt would shear off. Ten dollar bolts! I had bolts made, anti-seized all the bolts (9 of them) then just carried a cordless drill, a small bit and some self tapping screws along with a screwdriver. That really cut down on my expenses and down time.

Necessity is the mother of invention.

 

[firemanmike69]

[QUOTE="alchemysa;4545807" Comments to correct any bad advice I might be spreading here are welcome.[/QUOTE]

Use that method a lot myself, also works well on taps that get broken. I've also had good luck starting a pilot hole with a "centering" drill bit that machinists use, they have 2short flutes and are pretty short, not much length to break and enough to help locate/start a bigger bit

 

[alchemysa]

How big a bolt are we talking? ....

Love the welded nut idea.

Just to clarify. I was smashing the broken drill bit, not the bolt. The broken drill bit was only about 3mm this time, but I've used the method on larger broken bits. I think the bigger the bit the easier it would be as you can use a gutsier punch and have more room to move.

The bolts were well and truly rusted into a cast iron block of an old Wisconsin V4 that had been sitting in salty seaside air for years. I sprayed WD40 for a week, and tried a rattle gun, but in the end the heads of the bolts had to be snapped off to get the cylinder heads off the engine. But even then there was still plenty of exposed bolt left to get a grip with a pipe wrench. But no-way were those bolts going to budge. In the end i just had to snap them off at the base and start drilling. 7 of them!

 

[bffarms]

When I have a bolt broken in a cast iron piece I use a torch to cut\shave the bolt out. The bolt will melt before the cast iron will. Then I take a bolt and run through the threads to get the slag out of the hole. This works as long as the bolt goes all the way through the cast piece.

 

[Ivan49]

Use that method a lot myself, also works well on taps that get broken. I've also had good luck starting a pilot hole with a "centering" drill bit that machinists use, they have 2short flutes and are pretty short, not much length to break and enough to help locate/start a bigger bit

Just don't break the end of the center drill off. No fun to get out. We use to break drill all the time in the shop and we broke up the larger ones by shattering them. What was fun hen the tip broke off one 12 or more inches in the part. We did a lot of injector drilling and those had a carbide cutter edges on the heads
and those oles were 5 or more foot in to the parts. You had to shatter the carbide which then embedded into the part

 

[bcp]

I know a guy that has reverse drill bits. What a luxury.

Only a small luxury.

$7.99 for a set at Harbor Freight.

Left Hand Drill Bit Set 13 Pc

Bruce

 

[4570Man]

I've used this method for removing broken taps. Sometimes if you chisel them in the right spot you can get them to back out. I recently used an air chisel to remove a stuck nut. This was the fan clutch mounted on the water pump of my truck. I tried hitting an open end wrench with a hammer, but that didn't work. There's no way to get a socket and impact wrench oh this. I used an air chisel to break it loose.

 

[stuckmotor]

Only a small luxury.

$7.99 for a set at Harbor Freight.

Left Hand Drill Bit Set 13 Pc

Bruce

Thanks for the tip. I bought some individual reverse bits a while back and they were so expensive, I'm afraid to use them.