Stubborn swivel housing assembly bolts

Al2O3 said:

Going back to my apprenticeship days IIRC heating and slow cooling tempered steel. Heating and fast cooling (plunged in to water) hardened steel. This still depended on the carbon content. You could heat mild steel with a very low carbon content and then put in in to a carbon dust bath, the surface absorbed carbon and this case hardened it. I think you would have to heat it and fast cool it after the carbon bath.

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As what Al203 said, I'm probably being over cautious on the hardening of steel bit I guess. I've heard of needing to cool it as part of the process but don't know as much Al203. Either way, good luck. Every time I resort to drilling it seems to go wrong for me!

Another method is to apply heat and then run a candle over the broken stud, which melts and gets into the tread. (It has to be very hot) do this several times then use the extractor. Firmly but cautiously.

I would advise extreme care if using extractors remember the bolt was so tight that it sheared rather than turn so it will push the extractor, heat will definitely help because these bolts have a threadlock compound on them, and if you heat the bolt it will help to destroy the compound. Dont worry about hardening the metal only getting it very hot and quenching it suddenly would do that and it only works on high carbon steels.
I would suggest to try and make a center pop mark as close to the centre as possible then put a small pilot drill through all the way then drill it with slightly bigger drills until you get the biggest hole without damaging the threads, then heat it and try your extractor.
Dont be tempted by cheap extractors they can bring you lots of pain, dormer ones are the best I've used.
If you really take care and hit the centre its sometimes possible to collapse the bolt with a small chisel, when you drill it close to the thread.

Thanks everyone, looks like I'm going to be having fun shortly. Have ordered some dormer screw extractors & left hand drill bits.... should arrive tomorrow or Saturday.

Just to double check, Raywin in your post above - after I've drilled the pilot hole all the way through, and I've switched to slightly bigger drill bit... do I go all the way through again with that as well?

Yes.

SMG said:

Thanks everyone, looks like I'm going to be having fun shortly. Have ordered some dormer screw extractors & left hand drill bits.... should arrive tomorrow or Saturday.
Just to double check, Raywin in your post above - after I've drilled the pilot hole all the way through, and I've switched to slightly bigger drill bit... do I go all the way through again with that as well

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Yes I would, if its broken flush then the bit you are drilling will only be about 15mm as I recall, you can increse the drill size MM by MM untill you decide thats far enough, use the bigest extractr you can ( its stronger) and also you can put your flame onto the stud and it will pass through the hole so the heat will go right through it, spreading from within, spend some time to try and hit the middle as accuratly as possible it will make life easier,in the past I have used a set of dividers to check and if you were brought up by old time fitters they would show you how to use a centre pop to get a drill back on cetre when its running off slightly ( only applies untill the drill is cutting on full diameter)
Hopefully breaking down the locking compound will help you get them out as everyone says here heat can often make a huge difference, but dont try to force the extractors too hard or to jolt them just use even pressure.

Yippee... got the first one out without needing the extractors! Went in with 3.2mm RH drill bit, dead slow, loads of oil, and a little lego jig to keep the drill bit straight.... followed up by 4.2mm RH drill bit, which for some reason generated constant puffs of smoke despite the cooling oil.

Then tried my new 4.8mm LH drill bit, and she bit straight away and pulled the little tiger out!

Was bloody lucky... I thought I was dead centre....but I was soooooo close to hitting the threads at the other end, see pics below. Calling it a day now... end on a high and all that, will try the other one tomorrow.

SMG said:

Yippee... got the first one out without needing the extractors! Went in with 3.2mm RH drill bit, dead slow, loads of oil, and a little lego jig to keep the drill bit straight.... followed up by 4.2mm RH drill bit, which for some reason generated constant puffs of smoke despite the cooling oil.

Then tried my new 4.8mm LH drill bit, and she bit straight away and pulled the little tiger out!

Was bloody lucky... I thought I was dead centre....but I was soooooo close to hitting the threads at the other end, see pics below. Calling it a day now... end on a high and all that, will try the other one tomorrow.

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Excellent, well done
The heat from the drilling or grinding the head off or grinding a slot in the end is often enough. Not always though

Good luck with the other, it can help if you have someone to stand to the side and "sight " the drill for you I.e feedback to you to go up or down to keep the drill level, then you have to get your head over the drill to look out for any deviation side to side.

I'm restoring a P6 Rover and use a 50\50 mix of AFT fluid and Acetone it's the best penetrating fluid I've ever used...down here we call it miracle juice...

Nice job, hope you have as much success with the next one. Great to get feedback too.

I hate bolts. Spent 6 hours today unsuccessfully trying to shift it. Drilled through with 3.2mm RH bit like before as pilot... then 4.2mm RH bit all way through. Then switched to 4.8mm LH bit, but didn't get lucky this time..... got about 3/4 through but drill wouldn't go any further... hole pretty straight so I haven't hit threads.

Switched to 5mm RH bit to try and clear past the stubborn bit, but couldn't. Figured at this stage the hole was big enough for a screw extractor... so blasted hole with heat...... waited...... tried the screw extractor really carefully.. it bit... but won't dig in more than a mm... just sort of rotates even with firm pressure.

Took it out... blasted hole with heat again.... waited... blasted surround with heat again... waited... tried screw extractor again... swore.... repeated several times. Each time same thing, no joy, bites in about a mm then spins.

Am stumped ;(

Keep heating and applying anti seize, it will eventually penetrate and loosen, (not WD40) you could try the candle wax trick several times as well. You may be able to put extractor on the back to tighten it very slightly the back in the front to loosen it but do a lot of heating and penetrating oil cycles first.

As Scooby22 says, you'll have to go through heating and cooling cycles. I'd try and heat the flange, around the broken bolt, rather than the bolt as well. The bolt will heat up, obviously, but if the flange around it heats and expands more then that's beneficial. Have you got something you can accurately squirt cold water down the hole in the bolt with? If so, heat the flange around the bolt and then cool the bolt quickly.
You could then try the next extractor size down, but very carefully and gently!
If you could get the 5mm drill right through, you could possible get a 5mm bolt through it, tightened a nut on and it mught grip enough to allow you to use the 5mm bolt head to turn it out - just a thought

I've got some Innotec deblock ice that I could use to cool the bolt down... will try flange heat + innotec + penetrating oil on 15 min cycles for next few hours, see what happens....

SMG said:

I've got some Innotec deblock ice that I could use to cool the bolt down... will try flange heat + innotec + penetrating oil on 15 min cycles for next few hours, see what happens....

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Perfect
I had to google that stuff.
Have a cup of tea or coffee first!
If it's any consolation, we've all been where you are now and probably will be again. Those particular bolts are a well known PITA.
Good luck.

SMG said:

I've got some Innotec deblock ice that I could use to cool the bolt down... will try flange heat + innotec + penetrating oil on 15 min cycles for next few hours, see what happens....

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Try the mix 50\50 ATF and Acetone ir really Works...

I don't have any ATF around... is it similar to power steering fluid? Got some of that and the other half has some acetone nail polish remover.

SMG said:

I don't have any ATF around... is it similar to power steering fluid? Got some of that and the other half has some acetone nail polish remover.

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Yes it is.
I take it the cooling of the bolt isn't working

No, she's well and truly rammed in. Will give candle trick a go tomorrow morning... and if that fails will give up and get a pro in ;(

Am wondering if this bolt is super hard or something... it's resistant now to my drill bits, maybe that's why the extractor can't bite either.