getting broken bolts out of engine

You could make up a sort of punch to pick up the existing hole diameter, with a tip to centerpunch the remainder of the screw. From what you say it sounds like they are either 1/4 inch diameter or maybe M6.

Then you can use a good drill to put a pilot hole down the center of the screw - tough to do by hand but it is possible. Once the pilot hole is a few diameters deep you can switch over to a larger drill that is the tap drill size for that thread. Best is a left handed drill if you are willing to spend the money, as the stub of the screw has been known to simply unscrew during the drilling process.

Jim

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"RainLover" wrote: (clip) I don't think I could center the drill by hand on a broken screw (clip) ^^^^^^^^^^^^ Do I understand--you have exposed threads ABOVE the break? I would pre-drill a bolt, and then use it as a guide to center the drill.

Since you're not comfortable with using a screw extractor, I'd suggest calling a local machine shop, describe the problem, ask how much they want. Might be a lot cheaper than you'd think.

Being handy but not skilled, I've tried removing broken bolts myself and been unhappy with the time and frustration involved. Next time I'll be willing to spend $20-40 to save an hour or two of my time and stress.

Mike Patterson Please remove the spamtrap to email me. "I always wanted to be somebody. I should have been more specific..."

No. The entire bolt is about 3" long, but the portion broke is entirely IN the hole with about a 1/4" or 1/2" of 'hole' before the broken bolt.

I'm a good welder, but mechanical and this type of problem is as foreign to me as plate tectonics.

Thanks,

James

Like another poster said, pre-drill another bolt that fits the hole, and use that as your guide. Once you've got the guide-bolt drilled out, thread that puppy in good and snug, and then run the drill through it again to get into the busted off stub. Pull the guide bolt, and do the bolt extractor thing on the stub.

Probably wouldn't hurt to fill the holes and let the stubs marinate overnight in MM-oil, WD-40, or just about any other kind of penetrating stuff that could act as a lube to loosen things up as much as possible. I imagine you're looking at bolts that snapped due to the steel/aluminum thread-galling problem, so you're probably going to need all the help you can get.

Is the engine aluminum?

yes it is.

James, Seattle

Do NOT use an easy-out on this. You will only compound your woes.

Kroil. I would use Kroil.

And as mentioned, heat the aluminum housing before attempting to extract, this will effectively loosen the fastener because aluminum expands at a greater rate than steel.

Jim

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Ok, no threads, but the guide bushing idea will still work. Center drill a piece of round stock whose OD is a snug fit in the hole. This becomes your guide bushing to guide the drill bit to drill out the broken bolt. Once you get a pilot hole in the broken bolt, you can dispense with the guide bushing and start drilling out the bolt with progressively larger bits. You'll want to drill to just less than the minor diameter of the thread. Then you can use a pick to unwind the bolt thread from the hole. Should come out clean with no damage to the threads of the casting. But if it is obstinate, then you can use alum in the hole to eat out the remaining steel without harming the aluminum.

Gary

Again, use a left-handed drill. I used to pooh-pooh this idea until a co-worker asked me to drill out his manifold stud on his toyota 22R motor. He insisted on the LH drill and even got them from McMaster Carr.

Just as advertised, the remains of the stud spun out during the drilling process. Helps to go in at a bit of an angle so the drill grabs a bit here and there. I was trying to correct the position a bit and was angling the drill some when it spun out.

Jim

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Here is one method I have used to remove a sheared off bolt from aluminum casting.

Take a welding rod, say a 1/8 or 5/32 6010 rod and plunge it into the hole. The flux on the rod will prevent the rod from arcing to the case. Let it arc for a second or so then shut off the welder while holding the rod against the end of the bolt. You can then use the rod to unscrew the bolt. The heating from the welding will assist the removal of the bolt as the aluminum will expand more than the steel. The heat will also help break down any corrosion.

It could be risky to do this so if you don't feel easy with it, take it to a local machine shop or follow some of the other advise from the group.

Nitric acid, like eating out a tap. Do the bolt/drill bushing thing first. If you drill part way and then remove the bushing, switch to a lefthand drill. If it doesn't unscrew when drilling, drill thru and use the acid.

mj

On 14 Jun 2004 13:23:51 -0700, jim rozen calmly ranted:

Does anyone (big boxes?) besides Kano sell it? I'd like to try some.

Last week I took the remains of a 1/4 20 bolt out of my snowblower engine in about ten minutes, by following the instructions on a can of "PB Blaster". I had given up on it about 5 years ago, but a trip to NAPA in Port Huron got me the required product (it's also available at Wal-mart), also a neat key ring in the form of a miniature airline quick connect. I will not be without "PB Blaster" in future even if I do have to take SWMBO to "Mary Maxim" every once in a while! Gerry :-)} London, Canada

LH is a good idea, also IIRC nitric acid will dissolve steel and not Al.

Soak bolts in penetrant overnight. Rap on broken bolts lightly and rapidly with a small hammer and rod to vibrate them to help penetrant work it's way alongside them. Remove remaining two bolts, remove cover by working it over the broken bolts, then work with the exposed shanks of the bolts to remove them, hopefully with Vise Grips. Alternately, use the drill guide method to shorten the bolt shanks just enough to get the cover off, and back to the Vise Grips, or just drill through the bolt as others have suggested, staying at tap drill size or smaller.

RJ

If you ever have a flush or exposed shank of a broken bolt, just weld a nut to it, allow it to cool for about a minute, break the welded nut off, repeat. After a few attempts, it will turn out. The most nuts I haver ever gone through were about a dozen but sometimes they come out on the first try.

Shawn

Heck, if you've got enough bolt showing to thread a nut onto, weld the nut down solid, and just use a wrench to back what's left of the bolt out of the hole. If no threads, no biggie... Just weld the nut to the naked shaft, and proceed from there.

A busted blot that's sticking out is a no-problem problem. It's the ones that break off somewhere down in the hole that can severely suck.

A few months back there was a great thread on penetrating oils and I switched to PB Blaster. It's great stuff. I've gone through 4 cans of it working on a rusty car right now. The best method seems to be to soak the heck out of the part and let it sit overnight. In some cases, we've resoaked the problem part 2-3 times to make sure it gets to the base metal. Like Gerald, I highly recommend it.

--George