Drilling through metal for broken bolt on control arm using a cobalt bit not working

[ATCzMustang]

I have an 01' Cobra and when working on the rear suspension had removed the emergency brake cable mounting bracket and small bolt that is attached to the bottom of the lower control arm. Well the bolt snapped off, and all my attempts using bolt extracting techniques failed, and so I decided to just drill out the remaining bolt and through the metal to use a heli-coil or similar to rethread.

During this process I broke 2 drill bits off in the hole and there is still some of the bolt in the hole as well. I bought a quality cobalt drill bit and have drilled for 20-30 minutes and the hole is like the hardest, solid metal and I'm making zero progress it seems. I've tried low torque/low speed, high speed, everything and I'm not making progress. It seems that between the metal from the control arm itself, broken drill bit pieces, old bolt, etc. the heat has molded them all inside that hole to the hardest metal combination ever which I can't drill through.

I'm using a handheld drill and I can't get the control arm off where the hole is to use a drill press. I do have a 1/2" hammer drill as well I haven't tried and not sure if it's more powerful than the handheld drill. I also believe a lubricant is needed when drilling metal to keep it cool. I was using penetrating oil and spraying in the hole while drilling.

Again at this point all the metal in the hole has seemed to weld together and I'm way past any bolt extracting methods. I need to drill about another 3/4" to 1" through to have a hole all the way through. The hole size is roughly 3/8".

What in the world do I need to do, or technique should I use to drill out this hole? All the YT videos I watch make it like using the cobalt bit should chew up the metal and drill through, but that's not working for me at all. Maybe I'm not using the right torque and speed setting, but I tried multiple settings and none provided success. Maybe I'm not using the proper type of drill lubricant either and need to use a different kind. Please let me know a better method for drilling out this hole so I can repair it.

 

[Dave.O]

Those bolts breaking off is fairly normal. Happened on two of my irs’s. I always anti-seize those

Your approach is exactly how I repaired both of mine

If you are breaking bits, the drill isn’t straight, you are applying too much pressure or they’re dull. Just be patient and use oil, 3 in one or wd40 is fine. I actually typically use trans fluid when drilling and tapping

If you don’t care about stockness, abandon trying to drill out old bolt, start a new hole right next to it


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[ATCzMustang]

@Dave.O - thank you a couple of questions. What speed and torque setting should I use (roughly) on my handheld drill or should I use my 1/2" electric hammer drill instead? The cobalt drill bit I bought was new, do those dull out quickly?

 

[Fat Boss]

Where did you buy this cobalt drill bit? If it's a hardware store, just throw it away.

Get quality High Speed Steel (HSS) bits from a place like We're Sorry

I'd get several so you are always working with a very sharp bit. Jobber length is probably fine.

 

[ATCzMustang]

@Fat Boss - It's a Milwaukee Cobalt Bit. Also, can't the bits be sharpened on a grinder?

 

[Fat Boss]

@Fat Boss - It's a Milwaukee Cobalt Bit. Also, can't the bits be sharpened on a grinder?

That's actually garbage compared to a high quality High Speed Steel (HSS) drill bit. If you are really having trouble, you can get a tungsten carbide drill bit as well, but using in a hand drill you'd probably break it.

At MSC Direct you can get a 1/4" HSS drill bit for less than five bucks. Get a few of the size you need and get after it.

 

[SonicDTR]

I had to drill my super duty frame a while back and did some reading because it was a nightmare at first. From what I found, using nothing is better than an improper fluid such as wd40, penetrating lube, or oil. Even water is a better choice for drilling hardened steel than any of those. Sure enough, I just used a spray bottle of water to clean it out and took breaks to keep the bit cool and it worked much better. By design, most oils prevent the bit from actually cutting.

 

[shurur]

I had to drill my super duty frame a while back and did some reading because it was a nightmare at first. From what I found, using nothing is better than an improper fluid such as wd40, penetrating lube, or oil. Even water is a better choice for drilling hardened steel than any of those. Sure enough, I just used a spray bottle of water to clean it out and took breaks to keep the bit cool and it worked much better. By design, most oils prevent the bit from actually cutting.

I just use green grease...but yes it has to be something not binding.

Worse case you can use as small a bit as possible and hog around the broken bit, then pluck it out. Then just use a threaded insert (E-Z Lok).

Helicoil makes those as well and it fixes situations where you had to hog more material out. It also makes a much better fix that a helicoil.

I did this on my audi where the tensioner bolt sheared at the block. Folks were telling me I would have to replace the block and other stupid shit ideas.

When you drill the hole for the inserts, make progressive size drillings centered on the original hole where you plucked the broken bit from.

Anyway..that is the panzer fix for this problem.

 

[ATCzMustang]

I wonder about this? Great reviews:
https://www.lowes.com/pd/Oatey-Cutting-Oil/4752939

 

[01yellercobra]

I use zip ties. Every time I pull that wheel I think I should remove that broken bolt. Then I get distracted by something else.

 

[shurur]

I use zip ties. Every time I pull that wheel I think I should remove that broken bolt. Then I get distracted by something else.

Actually that is the fix for the '99, as there are no brackets for that year. Just loop some big honking tie wraps through the LCA spring holes.

 

[hotcobra03]

Drill press time.

If a piece of drill bit is still there it’s next to impossible

I would drill new hole next to it as suggested

 

[Dave.O]

I had to drill my super duty frame a while back and did some reading because it was a nightmare at first. From what I found, using nothing is better than an improper fluid such as wd40, penetrating lube, or oil. Even water is a better choice for drilling hardened steel than any of those. Sure enough, I just used a spray bottle of water to clean it out and took breaks to keep the bit cool and it worked much better. By design, most oils prevent the bit from actually cutting.

Interesting regarding drilling lube

Is that because ws40 or oil is too slick?


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[SonicDTR]

Interesting regarding drilling lube

Is that because ws40 or oil is too slick?


Sent from my iPhone using the svtperformance.com mobile app

That is my understanding. I am not an expert.

 

[ATCzMustang]

I use zip ties. Every time I pull that wheel I think I should remove that broken bolt. Then I get distracted by something else.

Unfortunate on my car the lateral movement is making all sorts of noises from the cable not being secured (inside the car at the ebrake) or I would have done this and called it a day.

 

[01yellercobra]

Unfortunate on my car the lateral movement is making all sorts of noises from the cable not being secured (inside the car at the ebrake) or I would have done this and called it a day.

You can use the zip tie to secure the cable. I've been doing that for about 5 years now.