Drilling Out Bumper Bracket Bolts - Need Advice

[sdk131]

I've been a DIY'er for years, and perform all of the standard maintenance on my vehicles. I even managed to install a new lift kit on my XJ this past spring that involved re-tapping some threads. However, I could use some advice on my current challenge.

I'm trying to remove the rear bumper brackets to make the hitch install much easier, and to do some rust treating/repair. However, all 8 of the bolts that hold the brackets to the unibody are VERY rusted and there was no chance of removal with wrenches (nuts and bolt heads very deformed due to rust). So, I have resorted to drilling them one by one. I don't have a lot of experience in this arena and the first bolt took me a good 15 minutes. With 7 more to go I thought I'd ask for some advice on bits, lubrication, etc. Any advice to speed this up....or is this just par for the course and I need to just suck it up and spend two more hours drilling bolts?

 

[MACH90XJ]

Can you get something in there to cut em out ? torch, sawzall ??

 

[ehall]

If you mean the 8 bolts in the nutstrips, its better to just snap them off and attack the problem once the nutstrip is out (or replace the nutstrip entirely). I had to use a breaker bar and a 3' piece of steel plumbing pipe to get the bolts off on mine, after trying various other tools including impact drivers. They all came out eventually, none broke.

 

[ParadiseXJ]

^^^
This.

If I could get a grinder up in there I'd prefer that...aka...grind them flush on the bolt head side and knock them out. If you are set on drilling them I'd use a new carbide bit (expensive, but they cut like butter) if you can find one. When I'm drilling thick steel or hardened bolts I use PB or some thread cutting oil.

 

[Hypoid]

I'm trying to remove the rear bumper brackets to make the hitch install much easier, and to do some rust treating/repair. However, all 8 of the bolts that hold the brackets to the unibody are VERY rusted and there was no chance of removal with wrenches (nuts and bolt heads very deformed due to rust). So, I have resorted to drilling them one by one. I don't have a lot of experience in this arena and the first bolt took me a good 15 minutes. With 7 more to go I thought I'd ask for some advice on bits, lubrication, etc. Any advice to speed this up....or is this just par for the course and I need to just suck it up and spend two more hours drilling bolts?

Like others have said, remove the bolt heads if at all possible. Past that, sharp bits, cutting oil, low speed and a lot of pressure on the drill. With a little practice, the last few should go much quicker.

 

[8Mud]

I use a drill around half the size as required. Then finish with the needed size. Pre drilling with a smaller bit, then finish drilling with a larger bit seems to work better for me.

Slow speed and pressure work better than speed. What you want to avoid is excess heat, which just dulls the drill bit.

If you use regular high speed steel bits (HSS), you really need to know how to sharpen bits. If you have to replace the bit every time it gets dull it gets expensive fast.

Cobalt bits are way good, they will cut through grade 9 bolts. HSS bits are usually good to grade 5 bolts. HSS bits rarely cut well or for long in grade 9 bolts.

I use the cheapest budget spray oil I can find, quantity is what saves your bits by cooling things down, not the quality of the oil. Used oil run through a coffee filter, thinned with diesel or even automatic transmission fluid also works well. Use one of those old hand pump oil guns to squirt it where you need it. Used synthetic motor oil filtered and mixed with automatic transmission fluid, maybe thinned a little (Acetone is the best thinner, but fire dangerous), works just as well as most penetrating oils.

 

[sdk131]

Pic attached for clarity. I can't get to these bolts with a grinder. I am wanting to remove the four bolts that hold each of these bumper brackets to the unibody.

 

[sdk131]

deleted double post

 

[ehall]

Ah those they are a bit harder to deal with but same advice. PB Blaster from the front and rear, then put the full monkey on a breaker bar with a cheater pipe. Bolts might come out or might break, but either way once the bracket is off you will have easier time drilling out the survivors.

 

[Hypoid]

Ah those they are a bit harder to deal with but same advice. PB Blaster from the front and rear, then put the full monkey on a breaker bar with a cheater pipe. Bolts might come out or might break, but either way once the bracket is off you will have easier time drilling out the survivors.

+1

Use a 6-point socket, hammer it onto the bolt head if you have to.

Not that it helps every situation, but give the bolt heads a couple solid raps with a hammer, like you are driving a nail. Sometimes it helps, but it never hurts the process.

 

[sdk131]

Well the banging on a six-point worked on all but two. The last two are rusted so bad that the heads are almost gone. Hopefully, that means the drilling will go much faster on those two. I also had not realized that they were bolts with captive/welded nuts on the unibody. I thought they were traditional nuts and bolts. Thanks for the tip, saved a bunch of time.

 

[Digger87xj]

cobalt drill bits

 

[denverd1]

If it comes down to drilling, use a slower RPM drill on a cord. Most corded drills are single speed so just bump the trigger to run it slower. Lots of pressure on it and some wd40 or cutting oil as a lubricant every 5 to 10 seconds.

 

[Renegade_Azzy]

Most normal drills dont have the torque needed to run at slow speed. If you have, or know somone with a geared drill/hammer drill, use that. I have a dewalt that makes short work of drilling steel becausebI can run it slow, but it still has enough oomph at that speed to throw you off. Be careful out there

 

[xcm]

Is an air hammer with a chisel tip available? might be enough left over to grab with a pair of vice grips.

 

[Matthew Currie]

It may be a little late now for this suggestion, but one thing I've had good luck with over the years is collecting cheap Asian sockets when they appear free or very very cheap. I have a bucket of them. For mangled or rusted bolt heads you can find a socket that's smaller than a proper fit, and hammer it on. In some cases where there's access, you can weld it on. Once the bolt is out, you throw it away, socket and all.