Drill bits recommendations? for drilling out a broken bolt

[visionguru]

When I was replacing the engine sub-ground cable on my Honda, stupid me twisted off the head of a 10mm bolt. Not a big deal though, I managed to find a screw hole on the engine and hooked the cable to body. Even without the cable, the car is still ok.

I still want to drill out the broken bolt, but I don't think my drill bits are any good. They are Craftsman, seem ok for drilling around the house. To drill out a steel bolt, I might need something better.

I'd appreciate recommendations of bits for this application.

 

[Indy125]

Left hand bits, I've had good luck with ones from HF.

 

[royesses]

If you want to go cheap get the left hand cobalt bit set from harbor freight. I used them to remove broken exhaust bolts on my daughter in laws grand am. I had to cut the drill down to get it in to some tight spots and didn't want to ruin my expensive bits. The drills actually worked great which astonished me. Or buy some Norseman cobalt bits or precision twist drill brand bits if you want high quality. Check out Harry J. Epstein's for the Norseman/Viking sets. I have a craftsman set that I loan out, they work ok on wood but will rapidly deteriorate on steel. If you want a full 118 piece cobalt set the harbor freight cobalt set for $90.00 has been very impressive. I've had it about 7 years now and have had no problems drilling steel, stainless steel, aluminum and chrome-molly etc. With 20% off they are a good buy.

Roy

 

[Thumper68]

Yup a left hand drill just smaller than the bolt, grind it flat if you can center punch it and if you can use a stubby bit to start the hole, then switch to your left hand bit and use a slow speed with as much pressure as you can, most likely it will come out before you drill all the way through.

 

[LXCam]

Bolt removal aside if this was the main ground between the engine and chassis I HIGHLY suggest you securely rig up the cable under a good solid connection for now. Yes there are normally plenty of grounds for current to find its path. But the last thing you need is a high current like the starter load going thru your smaller conductors like the coil packs or other electronic goodies. I've seen a **** load of damage done thru the years where the main ground was left off or loose and really burned up some expensive ****.

 

[ez-duzit]

Try the tip of a cobalt center drill to start the hole (so you can get sufficient pressure without breaking the bit), then cobalt drills sized to an EZ-Out. Left hand drill bits are unnecessary. Avoid HF ****. Buy quality.

 

[Olafur]

Decent HSS drill bit will do the job. Use slow rotation on the drill and some lube on the bit and good pressure.

 

[larry_g]

Left hand drill bits are unnecessary. Avoid HF ****. Buy quality.

I'm going to disagree with the idea that left handed are 'unnecessary'. They are not mandatory, but in my experience with a few dozen removals the left handed bit will catch and turn out most of the broken bolts. You can get by without them but with the success rate I've had with them make them well worth it.

lg
no neat sig line

 

[ez-duzit]

I'm going to disagree with the idea that left handed are 'unnecessary'...

I'm OK with that.

 

[scooby074]

Quality LH drillbit. LH arent necessary TBH, but probably 1 out of 5 times, the reverse rotation will spin out the broken bolt saving a step.

A better thing is to buy yourself a quality set of bits. Good bits will make drilling much easier, even for the around the house jobs. My favourite bits are the Walter SSTs. Good bits arent cheap though.

 

[kctyphoon]

I don't know if you'd have enough room for this, but years ago I broke off one of the fuel pump bolts on my monte ss that had a chevy 350 in it. Friend of my fathers told me to get a small chisel, and chisel in a slot on the broken bolt, then just use a flathead to back the screw out.. at 18 or 20 years old at the time, Id swear that guy saved my life with that.

 

[Bacon Man]

Today was the day a 1/4-20 won

Bolt was stainless and we broke over 16 drill bits and 5 easy-outs.
Cobalt, HSS, Left handers, Carbides and about a gallon of rapid tap and they hardly made a dent.

Eventually we heated it up to glowing red and smacked it through with a punch.
Then had to use a unibit to ream out the hole and retap it to 3/8

 

[anndel]

I've used LH twist bits by Drill Hogs to remove stuck exhaust manifold bolts that broke right at the head. Overnight flooding with Kroil helped as well.

 

[Olafur]

Perhaps off topic, but the first, second and third recommendation to remove broken bolts is a welder. Wast majority of broken bolts can be removed with welder with relative ease compared to drilling extracting...

Thats how the pros do it day in and day out in the rust belts of the world.

 

[bobcatdan]

Weld a nut to the bolt and turn it out.

 

[Tonyuk]

I would go with the LH cobalt bits, also with a smaller pilot hole as mentioned.

 

[Wamsutta]

I would go with a straight flute solid carbide bit; that way I know it will cut.

 

[DeadPedal]

Another vote for left hand drill bits for bolt removal. I had good luck getting a broken exhaust manifold bolt out with the harbor freight set. Worst case, the bolt doesn't come out while drilling and you're left with a holt to use an easy out in. Don't forget to use oil while drilling, and go slow with medium pressure.


Sent from my iPad using Tapatalk

 

[MikeF2316]

I've said it before, and I'll repeat it here. The closer to center your drill hole is in the broken bolt, the better off you'll be. Spend some time grinding the break flat, center punch lightly, then adjust it with angle center punch and harder hits to center it.

But I'll agree with the "weld a nut on it" folks. I just did that for the first time last month, and it worked perfectly, and in 10% the normal time. Of course, some times this isn't possible.

 

[visionguru]

Left hand bits, ....

.... the left hand cobalt bit set ... Or buy some Norseman cobalt bits or precision twist drill brand bits .....
Roy

....most likely it will come out before you drill all the way through.

....the main ground was left off or loose and really burned up some expensive ****.

Try the tip of a cobalt center drill to start the hole (so you can get sufficient pressure without breaking the bit), then cobalt drills sized to an EZ-Out. Left hand drill bits are unnecessary. Avoid HF ****. Buy quality.

Decent HSS drill bit will do the job. Use slow rotation on the drill and some lube on the bit and good pressure.

I'm going to disagree with the idea that left handed are 'unnecessary'. They are not mandatory, but in my experience with a few dozen removals the left handed bit will catch and turn out most of the broken bolts. You can get by without them but with the success rate I've had with them make them well worth it.

lg
no neat sig line

Quality LH drillbit. LH arent necessary TBH, but probably 1 out of 5 times, the reverse rotation will spin out the broken bolt saving a step.

A better thing is to buy yourself a quality set of bits. Good bits will make drilling much easier, even for the around the house jobs. My favourite bits are the Walter SSTs. Good bits arent cheap though.

I don't know if you'd have enough room for this, but years ago I broke off one of the fuel pump bolts on my monte ss that had a chevy 350 in it. Friend of my fathers told me to get a small chisel, and chisel in a slot on the broken bolt, then just use a flathead to back the screw out.. at 18 or 20 years old at the time, Id swear that guy saved my life with that.

Today was the day a 1/4-20 won

Bolt was stainless and we broke over 16 drill bits and 5 easy-outs.
Cobalt, HSS, Left handers, Carbides and about a gallon of rapid tap and they hardly made a dent.

Eventually we heated it up to glowing red and smacked it through with a punch.
Then had to use a unibit to ream out the hole and retap it to 3/8

I've used LH twist bits by Drill Hogs to remove stuck exhaust manifold bolts that broke right at the head. Overnight flooding with Kroil helped as well.

Perhaps off topic, but the first, second and third recommendation to remove broken bolts is a welder. Wast majority of broken bolts can be removed with welder with relative ease compared to drilling extracting...

Thats how the pros do it day in and day out in the rust belts of the world.

Weld a nut to the bolt and turn it out.

I would go with the LH cobalt bits, also with a smaller pilot hole as mentioned.

I would go with a straight flute solid carbide bit; that way I know it will cut.

Another vote for left hand drill bits for bolt removal. I had good luck getting a broken exhaust manifold bolt out with the harbor freight set. Worst case, the bolt doesn't come out while drilling and you're left with a holt to use an easy out in. Don't forget to use oil while drilling, and go slow with medium pressure.


Sent from my iPad using Tapatalk

I've said it before, and I'll repeat it here. The closer to center your drill hole is in the broken bolt, the better off you'll be. Spend some time grinding the break flat, center punch lightly, then adjust it with angle center punch and harder hits to center it.

But I'll agree with the "weld a nut on it" folks. I just did that for the first time last month, and it worked perfectly, and in 10% the normal time. Of course, some times this isn't possible.

Guys, thanks a lot for the recommendations. I learned a lot. Thanks!
Here are what I bought:
Grabit extractor
Irwin Colbalt 18pc drill bit set
Irwin Impact drill bit set
Tool Shop (Menards) titanium coated drill bit set with 1/4" hex shank
Tool Shop automatic center punch

Here are what I did:
I only used the Toolshop 1/4" drill bits. Center punch. I was able to drill a decent hole by starting small then go up, until the grabit #1 extractor fits.

The drilling part was surprisingly easy with my Craftsman 12v drill. Drill bits are not much of a concern.

Here is the result:
I broke the Grabit extractor inside, with not much force from my Snap On THLF72. I gave up on trying to extract that. Looking back, that bolt can only be taken out either by drilling or welding.

It's not critical to get the bolt out. The bolt is in the side engine mount bracket, which is a small cast aluminum part, cost $21 from Honda dealer.

 

[visionguru]

Here are the pictures. I hooked up the sub ground cable to somewhere else.

Sent from my SM-N910T using Tapatalk

 

[Ole Slewfoot]

This is why I usually start off with a nut and a welder.

 

[bw77]

Robinsons Auto just posted a video about removing rusted and broken off
bolts. First half of the video is about rusted fasteners, 2nd half he uses
the welding method to remove a broken shock mount bolt.

 

[MikeF2316]

Robinsons Auto just posted a video about removing rusted and broken off
bolts. First half of the video is about rusted fasteners, 2nd half he uses
the welding method to remove a broken shock mount bolt.

I like how close to the center of the bolt the drilling was! (So did the guy on the video.)

 

[Wamsutta]

Here is the result:
I broke the Grabit extractor inside, with not much force from my Snap On THLF72. I gave up on trying to extract that. Looking back, that bolt can only be taken out either by drilling or welding.

Try a Proto extractor next time. As long as you get the pilot hole drilled dead center, they always get the broken bolt out without damaging the threads of the part.

 

[TexasT]

If it is a bracket, pull it, weld or get a nut welded on and remove the broken bolt piece. I wouldn't think of trying to drill it in the engine compartment if you can remove the bracket. Put a washer between the new nut and bracket before the weld .

 

[theoldwizard1]

Yup a left hand drill just smaller than the bolt, grind it (the top of the broken bolt) flat if you can center punch it and if you can use a stubby bit to start the hole, then switch to your left hand bit and use a slow speed with as much pressure as you can, most likely it will come out before you drill all the way through.

Might be worth buying a pilot drill bit, especially if you can locate the center on your drill press table and lock it down.



I just watch Abom79 on YouTube remove 6 4mm screws using the above technique.