Bob Price

So I'm replacing the clutch in my 944S, and I've had my first adventure

How do you drill out bolts when you snap the heads off? I'm trying to get the transmission out of the car, and I snapped the head off the bolt that secures the rear end of the shift rod to the transmission (the bolt under the rubber boot on top of the tranny). Miraculously, it is possible to get a drill into the right position, but I've never drilled out a bolt before.

What size bit do you use?
What type of bit do you use?
How do you get out the bits of the bolt that will still be in the threads?
Anybody happen to remember how long this bolt is and how deep I should drill?

many thanks!

Ken

1. The size of the bit you use should be about 2/3 the size of the bolt. If it's too small, you won't do enough to the bolt to make it come out. If it's too big, you'll drill out the threads too, which is an even bigger problem. Along with this, make sure you get the drill dead center!

2. I've used regular metal drill bits, although i'm not sure of the type of metal that the bolt you're drilling is. If you dull the bit, get something harder!
(somebody else might have a better way to judge this)

3. Most of the bits should either come out on the drill bit. Kinda hard to explain, but when you're drilling, the bit 'grabs' the outer shell of the bolt and you can pull it out. If this doesn't work, once you're sure you've drilled most of the way through, take an all(ice pick) and just try and pull it out. After that you can spray some comressed air in there to get anything else out.

4. Not a clue. Just take it slow and you'll be able to tell when you should stop drilling. (the outer shell of the bolt will start coming out, or you'll hit something hard to drill through)

Good Luck!

Perry 951

Make sure you use an eazy-out bit (reversed bit). When you begin drilling, it will release some of the tension and just screw out. They are found at most parts and or hardware stores.

jim968

Actually drilling the bolt out risks totally buggering up the threads in the hole, if your drill isn't exactly centered & parallel to the bolt.

Instead, take the broken head with you to the local hardware store & ask for the correct size "Eze-Out" (Easy Out?) and matching drill bit. Get a good center-punch, too, if you've not got one. Probably cost $10-15 US for all of this, and you can use it many times, if you're unlucky enough to need to.

Center punch the broken end; drill per instructions with the Eze-Out; insert & seat Eze-Out. Turn CCW ("Lefty loosey, righty tighty"). the tapered end of the Eze-Out will tighten in the drilled hole, become wedged, and the bolt shaft will start to turn.

This does no damage to the threads in the hole in the part... which probably costs more than the hardware.

Jim, this post is composed entirely of post-consumer recycled typographical errors; no electrons were harmed in the composition of this post; as always, YMMV!

Dave951M

Bob-

Drilling out a bolt and removing it isn't hard. Get an EZ out kit and the appropriate drill bit. Go to the next size bit and extractor over the one recommended. (This is from previous bad experiences breaking ez outs.) Center punch the bolt before drilling. If the broken off part isn't flat, dress it off a bit with a file. You may even have to shorten your drill bit some too. Start drilling, putting drill lube on periodically. Drill slowly. Drill all the way through the bolt. Drill slowly. Keep checking the depth of the hole and comparing to the length of a matching bolt. When you get to the bottom, spray the bolt with PB and get the small pipe from some WD and shoot PB into the back of the hole. Repeat. Use appropriate ez out. Take your time. It's not hard. I had to remove a broken exhaust stud from #4 firewall side with an angle drill. Check the Pelican board and ninefiveone.com for the skinny on that one.

Good Luck
Dave951M

Tabor

Just out of curiosity, what do you do when the easy out breaks? The last time I had to drill a bolt out (and the only time), I had the easy out break. And it was very hard (i found it impossible to get through). I ended up just buying a new engine mount.

IceShark

Tabor, you are inconvenienced, but nowhere near as bad as snapping a drill bit off which we could have in this tight project. -g-

You can partially overcome snapped easy outs by heating and destroying the temper, then counter punch and drill the thing out square. when heat is out of the question, helps if you get into exotic drills that have diamonds on their toes and such.

In any event, doing the initial drill straight and square is of the utmost importance. And put a little more heat on it after that.

The big thing is to learn judgement on how hard to crank and not snap the thing off in the first place. When I was a real young kid we tightened 1/4 inch nuts as hard as we could and never worried. When you get stronger and also learn about leverage, you may get in trouble.

jim968

Tabor, no warranty on this advice, but the trick to not breaking them off seems to be to drill a large enough hole (diameter & depth, both) that the easy out goes far enough in that it's biting near its largest diameter. Tap it in so it really has a good grip. Then apply force to the wrench slowly, rather than giving it a sudden heave. This is pretty hard steel, which means it's going to be brittle.

And yes, if you break it, you will likely need to heat it to soften it before you can drill it out. That or rent a portable EDM machine (grin). Actually, a grinder bit in something like a Dremel tool or die grinder will remove it, but it'll be real, real slow, and eat a lot of grinder bits...

Jim, originally with a trade school education...

Dave951M

Like Jim and Dan said, drill straight and square and use the largest part of the diameter you can get in. I would like to add again that you should drill all the way through the bolt if you can. This helps to relieve some of the stress on the threads. Shooting some PB or similar penetrating oil into the back of the hole will get the oil working from the back of the bolt, assuming you've drilled all the way through. Becareful when drilling. Broken drill bits and ez outs are a major pain in the neck to get out.

Dave951M

jim968

Tabor, one more thought on not breaking easy outs: there are two styles that I've seen; one is a straight diamond-section, with straight flutes along two (IIRC) corners; the other has spital flutes. The spiral fluted ones seem to be a bit less hard and less brittle, and thus a little less likely to break. This is just an opinion, so take it FWIW. I've never actually done a Rockwell hardness test on either style.

Jim, gone to play forklift mechanic....

billybones

Just 2 more cents, I have this problem often.. Look into buying a left handed drill bit to start with.. well like 3.. one small and the next slightly larger.. Because you are drilling backwards a lot of times when you get half way thru the tension relieves and the bit bites and the bolt comes right out. You will have to go to like a J&L industrial store or something like that to get the reverse type drill... start with a small drill and move up in size after each drill thru.. till you are at 3/4 size of original bolt.. if it has not come out then put in an EZ out and try that. good luck.