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Hey guys, my 1993 Ford F150 kept throwing off the serpentine belt, and after some inspection I discovered that the alternator bracket was loose. In turn I discovered that the bracket was loose because the bolt that holds the bracket to the cylinder head was broken. I have been trying to drill this thing out, but progress is very slow. I’d estimate it is going to take me 18-20 hours to drill this thing out at the rate I am going. I’m using cobalt drill bits, but they hardly make any progress. Is there asecret to this? Or is this just a job that
is *supposed* to take 20 hours?
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I use cobalt bits and cutting oil for that kind of thing without a problem. Thing is that I’m using Snap-On bits and oil. I’ve used my home set of Craftsman Professional Cobalt bits and found them to be similar to tool truck quality. Bits other than those I have no good experience drilling steel with, which it may be a low quality bit issue. I know you’re using cobalt bits, but the quality matters and you get what you pay for, like the saying goes. It not even the metal the bits are made of that matters as much as how they are sharpened and heat treated. Heat treatment costs money and it a major defining factor in how well metals components and tools perform under severe use conditions.
Aside from that, there is a proper technique for drilling steel like you’ve got. First thing is to use cutting oil to lubricate and cool the bit. If the bit gets hot enough to make oil sizzle and smoke, then you are at the point where the heat treatment of the bit gets nullified/undone and it’s performance is immediately reduced. Second thing is to be having very low drill RPM but very high pressure (at least it feels that way by hand), 30 lbs pressure at a minimum. Drilling by hand for more than 5 minutes, I set up to push with my chest instead of arms using some padding. The trick is push hard and straight, and go a slow spindle speed (less than 100rpm) nowhere near any drill’s free speed RPM. Do your best to keep oil in where the bit is doing the work, which is easy on a horizontal situation like you have.
I’ve found over the years it is easier to weld a washer to the broken bolt then weld a nut to that washer, if enough of the bolt is sticking out you can just slip a nut over the broken bolt and weld rite to that. By the time you’re done you will have heated the bolt sufficient enough that it will usually back rite out. But if the broken bolt is recessed below the top threads this won’t work and drilling is your only alternative.
Try drilling at a slow speed with some sort of oil. You will find it will drill abit easier at a slower speed.
As an ex tap/die/tool maker, you are likely dealing with a hardened bolt. That’s most likely why it snapped in the first place, as they become quite brittle.
1. absolutely right mentioned – drill at slow speed.
2. you’d get nowhere without a center punch and pilot hole. What WILL happen is that drill bit eventually will fo into threads. And ruin them. That is not the goal of your exercise, right?
3. I’d suggest masonry bit, one that has carbide tip. You may need 2-3 different sizes, for pilot hole and expansion. Like this:
http://www.harborfreight.com/5-piece-masonry-drill-bit-set-43694.html
Pilot hole will prevent threads from bust. As you do not want to do all the drilling THEN followed by installing a heli coil into busted threads, right? Also, there’s a chance that when you widen center hole big enough, broken bolt extractor may yank what’s left out.
We used water/oil milkshake for composite alloys and stainless steel. Cools and lubricates. You can mix it in any kitchen mixer. Of course, safe to presume that you drill UP so it’ll run off bit right away.Guys, thank you all for your wealth of knowledge. With your help I have made some progress, but it is pretty clear that my hole is off center; though I have drilled past the bottom of the bolt. I tried to start off as close to center as possible, but it was a little bit difficult as I am looking down into the engine compartment and have to drill perpendicular to my line of sight. Am I now “out of the frying pan and into the fire”, so to speak? Any advice for me at this juncture? Thanks, Pop
You’re definitely into the fire at this point. The goal would be to open the hole up until you are interfering with the original threads in the hole. At that point, in my experience you MAY get a break and have become loose and removable at this point. The chance if this increases if you are using left-handed drill bits that you run counterclockwise instead of the normal direction. This is also the point where some light torch heating could start to be useful as well. Don’t drill or grind anything that’s just been heated up, as the drill or grinding bit can easily get hot enough to damage it.
Heating up what’s left of the bolt and tapping it with a punch may break it loose, but don’t go crazy. If it doesn’t work yet, you have to weaken some more by removing more structure to weaken its grip in the hole. You would ideally get a small grinding tool that fits in the hole that will grind sideways into what’s left of the bolt. Once it’s carved out like a C-shell, it eventually get thin enough that you can use a pick or something like that to catch the edge of it it and fold it in on itself. That is another time some heat may help to get it to come free, and of course some oil in there can help when it’s warm but not hot enough for it to boil and roll off (Leidenfrost Effect).
Good luck man, it’s an artform. Do your best to set yourself up to work comfortably. Doing this kind of a thing on trucks can justify setting up a scaffold to lay on, like setting a piece of plywood across the front of the truck and a ladder or something in front of it that is of equal height.
Ahem, you can still change hole direction but I dare not to explain this over the internet. Basically, you need one size up drill bit and go at the angle, on your pic, towards the R upper hand corner, scooting new opening that way. As you get deeper in, hole center moves over and then you can grab another larger size drill bit and go straight down. As it was said, it’s artform.
Btw, a flat head screwdriver, slightly modified on sides edges, may drive bolt threads out.
I think safest bet is to do what Fopeano said – Dremel it out.Next time you have a job like this, do not start with a small bit. Start with a bit that is an exact match to the hole diameter. Go straight in. You will loose upper thread and a half or so, but it will center itself into the bolt shaft and then you just follow the center with small bit.
I like to use a transfer punch to mark center on these. Before taking the bracket off get one that just barely fits in the hole. All the other bolts in the bracket would need to be tight obviously. Then tap it to mark the bolt. Once the bracket is off you can get a better mark with a good center punch.
Drilling bolts is tricky. Takes some knowledge to get right on center and a quality bit at the right speed as has been mentioned. Harbor Freight bits aren’t going to cut it and no bit that is unlubed and run at high speed will last, it just burns them up. Usually you learn how to do it right by going through the headaches of what happens when you do it wrong, as you are learning. I’ve been in your boat before, as I am sure everyone else who has responded to your thread so far have at one point. Very soon when under the hood you will be temporarily incapable of saying any word that doesn’t have four letters and start with F. These words will be uttered at a higher than normal volume and may later be repeated by any small children within earshot.
I try to avoid drilling at all costs. I would’ve built the head of that bolt out a little more with a welder and then welded a nut on like Beaird touched on, but that would not only require owning a welder but being a bit skilled with it. Its a skill I would recommend learning for the future.
Now that the damage is done, I would try the idea with the Dremel. Remember to go slow and not overheat the carbide you are using. You may be able to hog this out enough to get an extractor in it and break it loose. Once it is out, follow these steps:
1. take a deep breath.
2. drink very heavily
3. relax and tell yourself it was just a bad dream that is now over.left hand drill bit.
best solution to a broken bolt.
bolt remover “kits” have these bits that only kinda sorta remove stuck bolts.
have to pre-drill and such but if you just go ahead and use a left-hand bit ….
would suggest a punch or something to get a dip to start the bit.
you’ve already got a hole, a left hand drill bit should take it out pronto.yes, have to be careful as all mentioned above.
but it turns in the direction you want that left over bolt to turn.
and might just loosen up and spin out.
if not, you still get same effect as the above and have your hole.
can only win with a left hand drill bit – not lose.
again, same precautions as above.2 cents.
Thanks all for all the valuable input. I really appreciate it.
In the end I could not remove the broken off bolt, so I ended up getting a HeliCoil kit from NAPA, drilled it out and re-threaded the hole, and installed a new bolt. The bracket is now tight.
Also, in the course of this exercise I noticed the belt tensioner was fried, so I replaced it along with the belt. Truck is back up and running like a champ!
This forum ROCKS, and you guys, who are so generous with your time, experience, and knowledge, make it so.
So, a heartfelt THANK YOU for helpiong me and my family save money, and a ton of it at that, on car repairs.
[quote=”popoften” post=137639]Thanks all for all the valuable input. I really appreciate it.
In the end I could not remove the broken off bolt, so I ended up getting a HeliCoil kit from NAPA, drilled it out and re-threaded the hole, and installed a new bolt. The bracket is now tight.
Also, in the course of this exercise I noticed the belt tensioner was fried, so I replaced it along with the belt. Truck is back up and running like a champ!
This forum ROCKS, and you guys, who are so generous with your time, experience, and knowledge, make it so.
So, a heartfelt THANK YOU for helpiong me and my family save money, and a ton of it at that, on car repairs.[/quote]
Glad you got things fixed. Don’t you just hate it when something as dumb as an alternator bracket causes so much grief?
I came to late in the game , had a broken bolt on a lower intake manifold, something really hard to work while in the car. Anyway for future, try a drill bit called the rescue bit. Google it, only a few people sell it only. That stuff is awesome, it will drill out the metal. I ended destroying mine inside without any thread damage.
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