Broken stud - Drill problem


I need help.
I broke all 3 studs off my manifold so had to drill out the bolt and rethread with a tap.
When drilling out the broken bolt, I missed the center and also drilled at the wrong angle.
Any hints at making a perfectly aligned hole right thru the center of the bolt at the perfect angle?
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I soak the bolts well with liquid wrench, maybe overnight. Some light tapping will help the liquid penetrate around the threads.
As the drilling, I use a small bit to drill the center and gradually move up in size until I can get an extractor tool in tight. Then slowly remove the bolt.
Not a good idea to drill the entire bolt out in one try. Start small with the bits.
-- Oren
"The voices in my head may not be real, but they have some good ideas!"
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wrote:

Use a centerpunch to start off right.
you can also buy reverse twist dril bits,so the bit acts like a screw removed while it's drilling a hole.
--
Jim Yanik
jyanik
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Exactly. I soak the studs before (not in many years) then punch and hammer. Helps loosen the freeze early. The pilot hole IMO is the most important.
The better approach is only break one stud and learn, but not three.

I've got a 20 year old 5 piece Extractor Tool set....love it, but never need it (GRIN). -- Oren
"If things get any worse, I'll have to ask you to stop helping me."
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I meant to mention using a center punch. With a hammer and punch make a dimple in the center of the broken stud. This dimple will help in keeping the small bit from skipping around and going off center. Drill that pilot hole a move up in size.

Oren
"The voices in my head may not be real, but they have some good ideas!"
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I'm sure he's right about starting small.
Havent' done this ever but maybe if you put the manifold back on, you could use it to center and keep straight the larger drills, or at least the largest one.
I don't know -- does your replacement bolt have to be as big as original. Would making it a bit smaller be an advantage or cause its own problems? If it came loose could you then put the full-size or would that require a lot of extra work? Probably this whole paragraph is a bad idea, but you could ask a good mechanic.

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BTW, you didn't say how far you had drilled. Just a bit, or more than an inch, or what.

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wrote:

Nor, why his manifold has (ALL?) only three bolts.... or that the bolts are broken in the head and not the manifold. I missed it.
-- Oren
"If things get any worse, I'll have to ask you to stop helping me."
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If these studs were on a cast iron manifold your attempt at removal was all wrong. What has worked for mechanics for years was to use the rosebud tip on the acetylene torch and gently bring the casting up to red heat and then quickly use your Visegrips to unscrew the stud. Even with a broken stud you can add enough new metal with a MIG welder to grab the broken stud with Visegrips. Sounds like you will need to buy a new manifold now, sorry. HTH
Joe
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Joe wrote:

May be the easiest way out... what kind of car is this?
I'd suggest, if it is a common manifold, getting a replacement from a junkyard and then removing the studs (as Joe suggests) with a torch, and installing new ones with plenty of anti-seize. Use brass nuts to attach the downpipe, as well - they don't rust like steel and if the stud rusts badly enough to grip them tight they can be burned off with a torch and then you can rethread the studs with a die, assuming they don't come right out.
nate
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Actually, what I was looking for was an answer that included making a jig that would help keep the drill straight.
For instance, taking a 1 inch long piece of 1x2 lumber and drilling a hole in it. Then clamping this jig to the manifold with a couple of c-clamps and viola, you have perfect holes.
I paid $2.40 for each of the stud bolts. OUCH! The car is an 89 model so the bolts had become one with the manifold. And it was the other end of the manifold, not the part that attaches to the engine.
I was willing to drill a smaller hole but the tap and drill m12-1.25 was already purchased.
thanks
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