Extracting broken studs

[OwdChina]

Sometimes extractors do work, these came out.

 

 

 

 

 

Sometimes they do not because I have a limit on just how much force I will use on a extractor before I stop and put a left hand thread up the hole and use a L/H cap screw to get the bastard out. Breaking an extractor is going to cause a little job to turn into a bloody big one. 

This is the other bank with the same problem, back pot exhaust studs snapped. This one aint coming out with the extractor. Problem was I'd left the M6 L/H tap in England and didn't have time to wait for a replacement. Helicoil was my only other option..........just as good.

 

 

 

Increasing drill size from 5 to 8mm to accept the helicoil tap. Keep everything square

 

 

 

 

 

[vaughant]

I bought a set of cobalt drills from machine Mart t'other day for about 30 sovs and they've been immense, I've been using them in work and they fly though thick steel etc with no issues at all.

 

Ok you can get a standard set for half the price but these things have saved me so much time and effort, stuff I've had to gently use a pillar still on recently I can now drill in place with a cordless saving me hours of time.

[richardthestag]

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.

 

This ^^

 

and when the tap snaps off because it is too brittle for the job and too hard to drill out you will need to break it up with a very fine centre punch and extract in 1mm chunks at the time.

 

Cheap and China and ebay have caused me way more issues that it should have done.

 

I am always on the lookout at car shows etc for boxes of old school used unf unc taps. Collection is steadily building, Mrs thestag always asks "what are you buying that for you already have one?" my answer is along the lines of "yes but it is a British made 3/8 NC20 bottom tap and it still feels sharp"

 

</fnarr>

[John F]

This ^^

 

and when the tap snaps off because it is too brittle for the job and too hard to drill out you will need to break it up with a very fine centre punch and extract in 1mm chunks at the time.

 

Cheap and China and ebay have caused me way more issues that it should have done.

 

I am always on the lookout at car shows etc for boxes of old school used unf unc taps. Collection is steadily building, Mrs thestag always asks "what are you buying that for you already have one?" my answer is along the lines of "yes but it is a British made 3/8 NC20 bottom tap and it still feels sharp"

 

</fnarr>

 

Soz, my mistake - the tap's coming from the UK, the cap screw is coming from China (there were no UK ones listed for some reason).

[richardthestag]

perfect, the screw will be a lot easier to remove should it fail.

 

Alloy and steel has caused me bother other the years, especially anywhere near the water jacket. no amount of welded nuts etc are going to work! RV8 and Stag V8's are very very good at this scenario

 

Left hand extractors will just break, left hand drills will just chew the remains up, a left hand bolt threaded in will probably just break!

 

Sometimes I have to just accept that the thread is just too seized to the alloy, if it is not flush then I wind a nut on to help me centre the drill, if it is flush then I glue a nut over the thread for exact the same reason. flap discs are good at getting the broken end flat and centre punches are invaluable.

 

Then I have to drill progressively larger and larger holes, as big as I dare and use a centre punch to try shift the thread around. I particularly like JayW's sacrificial masonry drill bit idea. 

 

If no water jacket is nearby then I have had some success with extractors and grippers but more often than not some local heat and Stilsons will get it out.

 

My stag block had to have one of the slant studs spark eroded out, even engineering shop was worried about it as the thread was NOT perpendicular to the block face. £150 please. effective but expensive

[John F]

It's a stainless steel screw ffs, and it's the only one I could find at the time, stop trying to jinx this job

[Guest Hooli]

This reminds me, I need to buy a new tap wrench.

[Talbot]

I've done several snapped-off bits of steel in various locations over the years, and the main advice I would give is take your time.  If you try to rush, it will absolutely and catagorically get worse.

 

9 times out of 10 I can get a centre drill into the stud, then drill it out progressively to the root diameter of the threads, and then you can just pull the threads out with a pair of needle-nose pliers.  Extremely satisfying to see them come out.

 

Differential expansion due to heat will also work quite well, but just don't use more heat than anything nearby can cope with.  Made that mistake just the once.

[richardthestag]

It's a stainless steel screw ffs, and it's the only one I could find at the time, stop trying to jinx this job

 

stainless steel - tensile strength of warm butter 

 

[John F]

stainless steel - tensile strength of warm butter 

 

 

Ah fuck it, I'm just going to scrap the engine...

 

[richardthestag]

still at least the stainless steel will drill easily when it does seemingly melt under the slightest strain.

 

You doing it  on the bench or is the engine still in the bike? If the bolt just snapped without turning I would defo have it on the bench.

 

Drill right through it and soak it in coca cola (full fat)

 

if all else fails the head can always visit your local engineering shop or even be replaced with one that has good threads

 

not sure I can wait for your chinese stainless leftie to arrive the suspense is killing me

[twosmoke300]

Stainless is indeed weak as piss but can be a cunt to drill -lots of pressure and low speed to stop it work hardening

[Mally]

Personally I would never trust the strength of a stainless screw.  

Equally as said, its a bastard to drill.

Therefore I wouldn't use it to try and remove a broken stud in any circumstance.

[John F]

The engine's out of the bike but I can't get it under a pillar drill (I don't want to remove the head if I can avoid it). The bolt snapped off at some point back in the mid-1990s, I can't remember whether it happened during the accident that lunched the original bike it was in, or whether I snapped it off while removing what was left of the exhaust.

 

OK then, since I'm apparently crap at selecting the right screw for this job (in my defence, I'm not a trained engineer & I've not tried using this method before) - can someone post a link for a leftie M6 x 16 mm cap head screw that WILL do the job?

 

Thankyouplease

[richardthestag]

the thing for me is, you are going to lots of effort to drill a hole dead centre of the offending stud. why not continue to drill until the thread is all but a sliver. if you are working to m8, drill to m6 and attack it with a masonry drill bit in reverse. or hammer a torx bit in gently so as not the stretch the now hollow bolt remains

 

If that fails, keep going until m8, tap and fit an m8 helicoil.

 

why make it difficult?

 

http://www.ebay.co.uk/itm/DRAPER-Helicoil-Type-Metric-Thread-Repair-Kit-Set-Choose-From-M5-M6-M8-M10-M12-/291439254410?var=&hash=item43db221b8a:m:myj2iUcBUcpZNQpGVPYcMBA

 

edited to add, maybe the m6 lefty tap will wind out the remains? dunno, the issue is that if it breaks you into a world of pain

[twosmoke300]

Make it really easy and pop it in the boot of your car and take it to someone that is doing it everyday

[John F]

richardthestag, on 07 Aug 2017 - 7:01 PM, said:

the thing for me is, you are going to lots of effort to drill a hole dead centre of the offending stud. why not continue to drill until the thread is all but a sliver. if you are working to m8, drill to m6 and attack it with a masonry drill bit in reverse. or hammer a torx bit in gently so as not the stretch the now hollow bolt remains

 

If that fails, keep going until m8, tap and fit an m8 helicoil.

 

why make it difficult?

 

http://www.ebay.co.uk/itm/DRAPER-Helicoil-Type-Metric-Thread-Repair-Kit-Set-Choose-From-M5-M6-M8-M10-M12-/291439254410?var=&hash=item43db221b8a:m:myj2iUcBUcpZNQpGVPYcMBA

 

edited to add, maybe the m6 lefty tap will wind out the remains? dunno, the issue is that if it breaks you into a world of pain

 

TBH I liked meowdchina's idea & thought I'd give it a go. I'll probably end up drilling it out if that doesn't work, though.

 

twosmoke300, on 07 Aug 2017 - 7:50 PM, said:

Make it really easy and pop it in the boot of your car and take it to someone that is doing it everyday

 

Are you on the right forum? lol.

[mat_the_cat]

can someone post a link for a leftie M6 x 16 mm cap head screw that WILL do the job?

 

Look for a grade of 8.8 or even better 12.9, which relates to the strength of the fastener. No link, sorry!

[John F]

mat_the_cat, on 07 Aug 2017 - 11:45 PM, said:

Look for a grade of 8.8 or even better 12.9, which relates to the strength of the fastener. No link, sorry!

 

Thanks Mat, that's helped me find the bolt I need (black oxide coated EN 1.7220 equiv., strength class 12.9).

 

[John F]

Time for a quick update.

 

Here's a pic of the broken manifold stud - which, due to a measuring fuck up (otherwise known as a bad guess) by yours truly, is actually an M6 and not an M8. But never mind.

 

 

 

 

It hadn't broken off as flat as I first thought, but the centrepunch did give enough for a pilot drill to bite on.

 

My mate Josh did the actual drilling 'cos his eyes are way better than mine, and guess what happened?

 

 

 

 

Yesss! The broken stud wound out nicely with the 5 mm left-handed drill bit, as originally hoped!

 

I'm dead chuffed with Josh's accuracy at drilling the pilot hole though:

 

 

 

 

And here's the front of the stud, showing where the 5 mm left-handed drill bit into the stud:

 

 

 

 

Job's a good 'un

[richardthestag]

love it when a plan comes together

[John F]

I found another flush-broken fastener today, one of the screws that holds the signal generator cover on:

 

 

 

Out it comes, same method as before:

 

 

[Exiled_Tat_Gatherer]

Result!!! - Excellent reading too.

*touches wooden head* - never had this problem happen to me so far, been extremely lucky I suppose - but this is now bookmarked for future reference in panic mode!!!