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Old 02-08-2018, 10:49   #1
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Help with drilling out a stuck hex bolt

We have an old Whitlock steering pedestal where the top plate is held in plabe by two stainless steel hex bolts. These bolt into an aluminium throttle housing. Apparently they are supposed to be removed once a year and screwed back in with a healthy coat of tefgel or similar, but I reckon this hasnít been done in about forever. They are totally stuck!

Iíve tried soaking with WD40, heating, tapping with a hammer, impact-type drill, etc. but to no avail.

So I think my only other option is to drill them out? But Iím not sure exactly how to do this?

Is it literally just drilling straight through the head down the longitudinal axis with a drill bit that is a bit smaller than the diameter of the bolt?

Any guidance would be great!

Ps I can access the underside and can use a nut and bolt, so not fussed if the thread gets messed up.

Cheers
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Old 02-08-2018, 12:54   #2
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Re: Help with drilling out a stuck hex bolt

You made it sound easy. You need the correct size easy- out and drill bit for your screw. Might also need a cobalt drill bit and some cutting fluid. There are a bunch of different kinds of easy out, get one with coarse teeth and center punch the bolt first, very carefully. I needs to be in the center, or everything might go wonky.
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Old 02-08-2018, 13:02   #3
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Re: Help with drilling out a stuck hex bolt

1st poster has it dead on. I, do this when using an easy out. I, put maybe 4 layers of duck tape if possible then use my center punch to position my drill bit.
Tha tape will help steady the drill bit when starting.
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Old 02-08-2018, 13:29   #4
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Re: Help with drilling out a stuck hex bolt

I think if you can't undo it with a socket or spanner you will not have any more luck with an easy out.

You will have to drill it out like you say.

It will most likely be 316ss so it will work harden as soon as the drill stops cutting.

First though I would put a socket on the hex and try to undo it until it either comes out or the head shears off.

Assuming the head has now failed and you are looking at the broken bolt. Use a centre punch to pin point the centre. A light tap with a hammer and have a look if you are on centre. You can tap the pin point over on an angle if you are off a bit. Once on centre give the centre punch a decent hit.

Start with a new drill bit, or if you can sharpen drill bits sharpen it with less rake. If the bolt is 3/8. or 10mm I'd use a 4mm drill first straight through. Then a 6mm then an 8.5. At this point it has probably unthreaded it's self. If not go up in size until it clears out, then like you say, fit a nut behind.

If you feel the drills not cutting or you hear it squeel, stop immediately, go up to the next bigger drill bit and keep going.

Keep good pressure always on the drill while cutting, cutting fluid is good.
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Old 02-08-2018, 13:29   #5
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Re: Help with drilling out a stuck hex bolt

Absolutely. Easy-outs have a reputation for breaking and making a mess, but you are drilling into softer aluminum with a steel easy-out, so it should work very nicely. There are some brands that allow you to drill, reverse the bit, and extract.

You could also try an impact hammer, about $20 often with the right bits. Or if you can get some dry ice conveniently, cover the plates with a slush made of broken dry ice in alcohol. Freezing contracts the metals, often breaks corrosion without any danger from flames. If you repeat that 2-3x then use the impact hammer...almost everything can be moved.
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Old 02-08-2018, 13:36   #6
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Re: Help with drilling out a stuck hex bolt

Speed of the drill is important as well. Getting as close to center of the old bolt is definitely important. Stainless work hardens very easily. If the drill gets full & stops cutting the stainless will harden. Try this for rpm of the drill: 140 divided by the diameter of the drill you should get a high speed steel drill to stand up reasonably well. Good luck
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Old 02-08-2018, 13:36   #7
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Re: Help with drilling out a stuck hex bolt

centre punch the hex head and using a small drill drill a guide hole to a depth equal to the thickness of the hex head.

Then using a drill slightly larger than the diameter of the bolt drill through the hex head until it comes off.

You should now be able to remove the top plate and have a stub of the bolt sticking up which you can grab with a vice grip and attempt to work the bolt free.

If you cannot work it free you can keep drilling down the bolt.
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Old 02-08-2018, 13:51   #8
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Re: Help with drilling out a stuck hex bolt

yep, forget easy outs - wont work. You could try hammer and screwdriver on the rim of the hex bolt - this worked for me on a motorscooter front brake that had a stripped hex head, but i doubt it will work where the metals have become chemically welded, worth a try though. If drilling try a bit of rocol rtd on the bit, will keep it sharp and lubed, and helps dissipate heat. Put a skinny drill through first then one about 1/16" to 1/32" smaller than the existing bolt or, as you dont need to save the thread, just go full size.
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Old 02-08-2018, 14:05   #9
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Re: Help with drilling out a stuck hex bolt

Bonus that the backside of the hole is open. Ditto above in drilling it out with progressively larger drills. Once decently sized the remaining bolt shell may start to screw right out through the bottom, provided the hex head has been snapped off. You can get threaded inserts if the drilling goes south or you end up stripping it while wrenching. Good luck.
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Old 02-08-2018, 19:24   #10
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Re: Help with drilling out a stuck hex bolt

Left hand drill bit might help, too.
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Old 02-08-2018, 21:32   #11
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Re: Help with drilling out a stuck hex bolt

How much heat did you try? Drilling comes second or as last resort. What size fastener are we talking about?
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Old 02-08-2018, 21:43   #12
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Re: Help with drilling out a stuck hex bolt

Thanks for all the replies. Bloody hell, not that straight forward!

I might start with drilling a small centre hole.
Then Iíll try conventional ďunscrewingĒ until the hex head strips.
Then Iíll try drilling off the hex head and removing the plate, then having a crack with the vice grips.
Then Iíll try drilling the whole thing out all the way through.

As a last resort, Iíll just buy a new steering pedestal [emoji23]
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Old 02-08-2018, 22:04   #13
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Re: Help with drilling out a stuck hex bolt

Start with a small center hole as close to exact center as possible. Let's say about 3/16". Then drill out to a size just under the bolt diameter. Let's say 1/16th inch under. when that bit gets down into the bolt the pressure being exerted by the aluminum corrosion will be relieved and the bolt may free up. If it doesn't just turn the hex head until it tears itself apart.

Do not remove the bolt head as others have advised. That will make it harder to get the rest of the bolt out.

As others have said: Drill very slowly and don't let it get hot. Once stainless gets hot it will work harden and you will never get it out. Use new drill bits and go very slow. The time spent drilling slow is far less than the time you will spend if you screw up. If you break the bit off inside the hole you're screwed.
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Old 03-08-2018, 01:58   #14
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Re: Help with drilling out a stuck hex bolt

I drill the heads off bolts and screws all the time and have a lot of success with screwing out the stubs. I have an old pair of vice grip locking pliers that I've had for over 50 years which I always use for that chore as none of the more modern ones do the job as well. If the stub is long enough you can tap it with a hammer as you apply torque which often helps. If you centre drill with a small drill you are no worse off than leaving the head on as you can just continue drilling the bolt out anyway.
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Old 03-08-2018, 09:05   #15
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Re: Help with drilling out a stuck hex bolt

Lot of good tips posted so far, my 2 cents worth;

There is a hand held impact tool that I have used, you can get a cheap one at harbor freight. It is hit with a hammer on one end, the other end has a socket adapter and it also comes with a blade and phillips bits. Cut off a piece of the hex wrench that fits your screw, insert it in the same size socket, insert tool into stuck screw, whack away with hammer. The jolting along with torque might loosen it.

2nd - if the hex head is not flush and you can get a vise grip on it, have someone apply pressure counterclock wise while you work the impact driver.

If this fails, using a hex wrench and a helper, piece of pipe or additional leverage as well as the vice grip, attempt to unscrew until you are successful or the head breaks off of the bolt. Try turning in also, sometimes a stuck bolt will move a bit tighter when it won't back out. Worth a try,

OK, so the head is broken off, use a dremel to grind the stub flat. Mark the exact center and center punch, drill out using a bit a slight bit smaller than the bolt. Try and easy out once the hole is completed but do not get overly aggressive. A stuck easy out is one of the hardest things to get out since it is hardened steel and wont drill worth a dam.

When all else fails, drill a size over and tap to the next size up bolt.'

Perseverance is the key.

Or just leave it alone until there is some dire reason for getting it out.
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