Extracting broken studs

[John F]

I'm sure we've all been here, and in the past I've had good results in the past by welding nuts onto the stud, etc.

 

But this one's a bit different. It's a steel exhaust stud that's snapped off flush in a recess in an alloy motorbike cylinder head. I can't get in there with a welder, or any other tool I'd usually use. Also, the broken stud has been in there since about 1996 at a guess.

 

I'm reluctant to drill it normally & then try to remove the stud with a left-handed tap, since it's a fairly small bolt (M8) and if the tap shears off in the stud it'll be a bitch to remove.

 

So, has anyone had any experience using left-handed drill bits on broken studs? The theory seems to be that the stud might unwind during drilling if the generated heat overcomes the bimetallic corrosion bond.

 

I'd be interested to hear if anyone has actually had a result using this method.

[JayW]

I've had various successes with lefties so they do work in certain circumstances.

 

Small extractors never work if the stud itself is stuck, they're not strong enough (engineering 101), but... I would usually drill the pilot hole out with a decent drill bit, then insert a similarly sized blunt (or masonry) bit and keep drilling to build up heat as far as I dare. This is normally when smoke appears from the thread.

 

The extractor will then normally wind it out. Has worked MANY more times than it has failed, it's all about building up the heat in a confined space - something you can't do with a blowtorch.

[Mally]

I've had them unscrew with a left handed drill. 

Never had much luck with stud extractor though, I always break the small ones, then its worse.

Heating it up a little first may help.

My biggest problem is hitting the exact centre of the stud.

 

Check out Spark erosion, that's the way to go from what I've heard.

Not sure it works on alloy though.

[Dead_E23]

I was intrigued by this method on YouTube; dissolving the bolt using Alum, which leaves the aluminium untouched.    

 

His other videos are well worth watching too, if you're interested in how things are put together.

[alf892]

Can you get it really hot first then quench it? Because of differing rates of expansion/contraction this can help....maybe not free it but make it a bit less stuck!

[John F]

I might be able to get some heat into it with a blowtorch, but I'm wary about using oxy-propane on it due to the ally head.

 

A mate of mine mentioned spark erosion but I couldn't do that myself, it'd have to go into a specialist - I'd like to avoid that if possible.

 

I've ordered some 2 mm and 3 mm left handed drill bits, when I get chance to work on the stud I'll report back on my progress (or lack thereof).

[John F]

I was intrigued by this method on YouTube; dissolving the bolt using Alum, which leaves the aluminium untouched.    

 

His other videos are well worth watching too, if you're interested in how things are put together.

 

Haha, that's a very entertaining Canadian!

 

And a genuinely interesting method. Not sure I'd be able to use it on my stud though, I'd struggle to seal the area around it. But it's worth remembering.

[Des]

I've just had to remove the remains of a bleed nipple from an aluminium wheel cylinder, had replacements but wrong size, fuck you amazon, ready made hole down the middle invited me to hammer a torx bit in with the intention of then carefully winding it out, snapped the bastard hammering didn't I, so I tried welding 3 or 4 penny washers and nuts on with no joy, then just built up a snot direct to the nipple bit and added a pair of ears for grip and out she came, slotted up the other nipple for a thread chaser and it's as good as the day Nissan cast the monkey metal. It was probably the repeated heat cycles of numerous attempts that worked here.

 

[jonathan_dyane]

Is the other stud ok/can you use the exhaust bolted on with one stud as a drilling guide with metal sleeves to fit the bolt hole?

[Arthur Foxhake]

When I did my broken manifold stud, in situ, I used an oversized bit that matched the manifold hole and used it as a centering drill. It took a little while but the oversized bit started to drill out the centre of the stud so I could get a decent pilot bit started in the right place.

That way you minimise the chances of drilling off centre into the ally head.

[Guest Hooli]

I managed to drill one out on my 14 once with the engine still built up. As I didn't get it perfectly straight & damaged the thread on one side it was rather lucky there was 1" of unused & undamaged thread behind the stud. One longer bolt later & all was good.

[Bren]

I got a broken bleed nipple out of a brake caliper by welding a pozidrive bit to the stub and then unscrewing it with a spanner.

[twosmoke300]

Go to your local engine rebuilding place and ask them to do it. Strip off as much as you can to make it easier and cheaper . They are doing it all the time and don't charge as much as you think and certainly not as much as another head .

 

I have a chap near me that does loads as homers and only charges about 20 quid . Any critical or bastard ones I get him to do them now . Amazing watching him work too - all freehand but drills holes like a bullet from a gun .

[Asimo]

I have had a broken tap spark eroded from an aluminium part. Expensive, but in the last resort........

[bunglebus]

Off topic a bit, but bI had a guy in a motor spares/tools shop insist left-handed drill bits didn't exist, when I'd been using them for years at my first job at a wood machine tool manufacturer. I've tried welding, drilling, easy* outs, all pretty much without success over the years. 

[sierraman]

Go to your local engine rebuilding place and ask them to do it. Strip off as much as you can to make it easier and cheaper . They are doing it all the time and don't charge as much as you think and certainly not as much as another head .

 

I have a chap near me that does loads as homers and only charges about 20 quid . Any critical or bastard ones I get him to do them now . Amazing watching him work too - all freehand but drills holes like a bullet from a gun .

Sound advice.

[cobblers]

Watching someone good do it makes it look so easy. I'm far from great but when I told the apprentice at work to drill the head off a screw today he made me realise how much skill it takes to actually do a half decent job, and that's the best I can muster.

 

Drill bits don't actually put much torque on the part, there's no point in left hand ones. Just like easy outs, they'll just snap before they actually wind out a properly siezed in stud.

You need to get a good center drill on it, open that out in stages til you just break through and then pick out the remains.

Helicoils are incredibly quick and easy so don't spend too much time trying to preserve the original thread.

 

Like twosmoke says, if the part is very valuable, the best thing is to take it to a place that does this stuff all day every day.

 

Removing a 100ish pin ecu main socket is a nightmare for anyone to do at home, even with the best "home" tackle   you can imagine.

I do it in a ten minutes at work without thinking twice. Not because I'm a god or owt, I just do it all the time. Even the apprentice who can't drill the head off a screw can do it.

[lexi]

Any time I find it difficult to get a weld on a stud with mig, the stick welder with a rod bent to shape can get in better. Your head may be delicate mind.

  My other weapon was the oxy/acy jewelers torch with the tiny pencil flame, but very hot and direct.

[matty879]

ive been here more times than i care to mention,i have a snap on(sometimes snap off) extractor set with the left hand drills,ive had some success with the bit simply winding the stud out while drilling,never on a manifold though,i would order a head set,get an engineer to remove the stud then deckoke the head and give it stem seals.better than wrecking the head.

[OwdChina]

Yo........I do a lot of these.

 

First you need a dot punch and hammer, and put a dot right in the middle of the stud.

 

Then a pilot drill (3mm) making sure you are in exact center of the stud and following its path/angle. You'll need to go gentle because don't want to drill through the stud and then start drilling the alum head. Half inch deep will be plenty.

 

Then a 5mm to open the hole to accept an M6 LEFT hand tap.

 

Now you need a M6 left hand Cap head screw.............sometimes known as an allen screw 20mm long. If you've drilled through the stud you'll need to lock the screw to the depth of the stud.

 

Cap screws are very strong and your stud will come out. Sounds a lot of work but it really only takes a few minutes.

[Guest Hooli]

I tried buying a left handed machine screw the other month, can't order them anywhere. Not even the local nut n bolt specialist!

 

Where can you buy such things?

[Mally]

http://www.ebay.co.uk/itm/M6-M8-Grade-8-8-Carbon-Steel-Left-hand-Thread-Hex-Socket-Head-Cap-Screw-Bolt/282273258656?_trksid=p2045573.c100507.m3226&_trkparms=aid%3D555017%26algo%3DPL.CASSINI%26ao%3D1%26asc%3D45398%26meid%3Df26d2a5cd7714311b0dd9a8934397553%26pid%3D100507%26rk%3D1%26rkt%3D1%26

[tooSavvy]

Off topic a bit, but bI had a guy in a motor spares/tools shop insist left-handed drill bits didn't exist, when I'd been using them for years at my first job at a wood machine tool manufacturer. I've tried welding, drilling, easy* outs, all pretty much without success over the years.

 

When I did my engineering apprenticeship I never saw/used/needed a LH drill.

 

I understood LH threads for rotational security (spin on/tight) and lathes etc.

 

It was only when we got a film [yes, that old] about 'the war & mass production' and a comment referred to large drilling machines having spindles counter rotating (basically a set of interlinked cogs) in a 'box'. The film clearly showed drill flutes rh/lh/rh/lh...

 

Jeeze... Things you remember/Things you don't

 

 

TS

[Mally]

When I did my engineering apprenticeship I never saw/used/needed a LH drill.

 

 

 

 

TS

 

When I did my engineering apprenticeship one of the instructors had a 3/8" LH drill.

He used to give it out now and then when you needed one and watch to see how long it was before you realised.

If you were clever you put the drill in reverse, drilled the hole and gave it him back without comment.

[John F]

meowdchina, on 05 Aug 2017 - 03:19 AM, said:

Yo........I do a lot of these.

 

First you need a dot punch and hammer, and put a dot right in the middle of the stud.

 

Then a pilot drill (3mm) making sure you are in exact center of the stud and following its path/angle. You'll need to go gentle because don't want to drill through the stud and then start drilling the alum head. Half inch deep will be plenty.

 

Then a 5mm to open the hole to accept an M6 LEFT hand tap.

 

Now you need a M6 left hand Cap head screw.............sometimes known as an allen screw 20mm long. If you've drilled through the stud you'll need to lock the screw to the depth of the stud.

 

Cap screws are very strong and your stud will come out. Sounds a lot of work but it really only takes a few minutes.

 

That sounds like an excellent method, I've ordered in the bits to do it.

 

I've gone for a 16 mm allen bolt though, I don't know how much length there is on the stud.

[OwdChina]

I tried buying a left handed machine screw the other month, can't order them anywhere. Not even the local nut n bolt specialist!

 

Where can you buy such things?

An engineering supplies should be able to get them no problem. I used to use "Able (abel) Fasteners" when I was in Rugeley and "AT Engineering supplies" when I lived in Lancaster. No idea what's in Doncaster though.

That sounds like an excellent method, I've ordered in the bits to do it.

 

I've gone for a 16 mm allen bolt though, I don't know how much length there is on the stud.

If it is the manufactures stud there will be a gap between the bottom of the hole and base of the stud. But to be honest you wont need to go that deep, 10mm should do it. A good spray of plus gas never goes amiss too.

[Guest Hooli]

Yo........I do a lot of these.

 

First you need a dot punch and hammer, and put a dot right in the middle of the stud.

 

Then a pilot drill (3mm) making sure you are in exact center of the stud and following its path/angle. You'll need to go gentle because don't want to drill through the stud and then start drilling the alum head. Half inch deep will be plenty.

 

Then a 5mm to open the hole to accept an M6 LEFT hand tap.

 

Now you need a M6 left hand Cap head screw.............sometimes known as an allen screw 20mm long. If you've drilled through the stud you'll need to lock the screw to the depth of the stud.

 

Cap screws are very strong and your stud will come out. Sounds a lot of work but it really only takes a few minutes.

 

Only one thing I'd add to that.

 

Grind the top of the stud flat before you start, or you'll never get the hole accurate.

[John F]

It's fairly flat anyway, but the centrepunch should give the pilot drill something to bite on.

[OwdChina]

It's fairly flat anyway, but the centrepunch should give the pilot drill something to bite on.

The centrepunch will give you a starting point, but you can move the drill position around a fraction by gently drilling slightly out of square in the direction you need to move the dot and at the same time bringing the drill into square then stop and eye up where the starting point of the drill bit mark is regarding the centre of the stud. It needs to be spot on in this case because there is very little room for error.

Because I do a lot of these I nearly always use 6mm..................nearly always.............on reflection in this case before you start drilling John maybe a 5mm tap and screw is a better option.......just a thought. Got some pics of a helicoil job I did on the truck which I posted to this site somewhere, i'll look for em and put em up.............may help.

[John F]

meowdchina, on 06 Aug 2017 - 8:23 PM, said:meowdchina, on 06 Aug 2017 - 8:23 PM, said:

The centrepunch will give you a starting point, but you can move the drill position around a fraction by gently drilling slightly out of square in the direction you need to move the dot and at the same time bringing the drill into square then stop and eye up where the starting point of the drill bit mark is regarding the centre of the stud. It needs to be spot on in this case because there is very little room for error.

Because I do a lot of these I nearly always use 6mm..................nearly always.............on reflection in this case before you start drilling John maybe a 5mm tap and screw is a better option.......just a thought. Got some pics of a helicoil job I did on the truck which I posted to this site somewhere, i'll look for em and put em up.............may help.

 

Yep, I'll make sure the drill is central.

 

I did order a 5 mm drill bit for the M6 tap and screw, the tap's coming from China though so it'll probably take a month or so to arrive.