Removing snapped drill bit...

Discussion in 'Engineers' Talk' started by Devil's Advocate, Jun 15, 2012.

  1. So, M6 bolt had snapped off flush in an alloy head, so's I gets my stud extractors kit and drills me a 3 or 3.5mm hole in t'broken end. Until I wobbled a bit. And the bit snapped clean and flush.

    So, I have an M6 mild steel bolt with an M3 HSS core :)'() sitting in an alloy head. How do I remove the barsteward? Obviously, my other drill bits are no harder than t'embedded one.

    At the mo' I am trying to use a sharp centre punch to chip away at the 3mm drill, followed by an attack with an M5 drill (I've given up trying to extract the original bolt - I'm just goign to re-tap it M6). Repeating ad nauseam.

    Any better solution? Are there any 'super-hard' drills out there. (Hmmm, thought to oneself- how would a masonry drill fair?!)

    Ta very muchly.
     
  2. Captain Leaky

    Captain Leaky New Member

    You either need to put the head in a vice and use a pillar drill or try welding a 'stub' onto the broken stud. I have done both in the past when restoring old motorcycles. Not easy either way.
     
  3. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    I assume it's of the type where you don't have access to the bottom of the bolt ?

    Mr. HandyAndy - Really
     
  4. Yeah - no access. It's a lawn mower engine.
     
  5. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Alright, then, would I be surprised if you said the the head has not yet been removed ?

    In other words is it sheared off flush with the head cover, or sheared off below the head cover and flush with the mating plate(head removed) ?

    Mr. HandyAndy - Really
     
  6. removed 7

    removed 7 New Member

    A salutary lesson never to use cheap drill bits - particularly when drilling steel bolts in aluminum threads.



    Mr HA has asked a most pertinent question here.........


    How's your botty today, Dev's?


    Lucia x
     
  7. Mr Ha - no, the head has not been removed. The stud in question is one of the exhaust-securing bolts, and the 'other end' of the hole - which isn't actually open - is lost amongst the cooling fins. The exhaust is removed, and the stud has snapped flush. Removing the head (or whole engine) would certainly allow it to be tackled by a pillar drill, but wouldn't actaully improve access as such.


    <h1>Anyways, Looch, 
     
  8. removed 7

    removed 7 New Member

    Dev's dear:  have you considered dumping that lawnmower and buying a replacement?

    I'm just itching to get to the bottom of this matter........


    Lux
     
  9. Captain Leaky

    Captain Leaky New Member

    This thread could run and run. It may be a bottomless pit. A dark orifice of hidden pungency....
     
  10. Looch, it's Stiga Combi Pro 55S with a Honda GCV160 engine. New price circa £800

    I bought it last yaer for £46 and restored to nigh-on perfect conditon. Tried her out - and the grass just looked up at this monster coming towards it and keeled over in defeat. Awesome, man. Anti-vibe deck an' everyfink - like being gently massaged with Oil of Ulay.

    Except there was a teeny, tiny exhaust noise coming from a not quite tight bolt. Which I tweaked.

    The rest, as they say, is a foffin' nightmare.

    Replacement m'botty.
     
  11. Captain Leaky

    Captain Leaky New Member

    DA, you are the same age as me, you must have 'fixed' a fair few Honda motorcylces as a youngster. They always snapped their head studs. Take the barrel off and get it helicoiled.
     
  12. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Can you get a hacksaw in there ?

    If so, could you cut across the flange and the bolt AND the drill bit to make a decent groove for a hefty screwdriver (meaning decent strong)or impact screwdriver ?

    If you can, and try the drill bit sized screwdriver first, you may be able to 'untwist' the drill bit. If not the whole bolt.

    2mm deep groove rquired.

    Mr. HandyAndy - Really
     
  13. Cap'n, to Helicoil you need to drill the foffer out first. That is my problem.

    Mr Ha, the bolt is - snapped - flush - with - the - alloy - head. I cannie hackie the stud without foffing the ali surround too.

    What? Me tetchy? Nah...

    I'm gonna buy a score of 5mm jobbers and go at it - a pidly 3mm drill ain't gonna win over tha'. Surely?
     
  14. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    If it's the exhaust flange, a 2mm cut straight across the hole will not harm.


    Mr. HandyAndy - Really
     
  15. removed 7

    removed 7 New Member

    Of course it's the exhaust flange, Mr HA!   That's why our Dev's doctor pointed the finger at him..........



    Lucia x
     
  16. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Well I guess there's nothing worse than having a bit stuck in your exhaust flange, unable to get it out no matter how much you try to screw it.

    But a slit in your flange mating surface will not damage it or make it fart under pressure because the gas comes out of the hole in the middle and the slit need not be filled.

    Mr. HandyAndy - Really
     
  17. That's fairynuff, Mr Ha - the exahust only seals in the round 'ole betwixt t'two studs, so some damage to the bolt flange ain't a problem, (tho' I'd hate to do it).

    Howver, with the other seized & snapped stud (yeah - both went) - which I did manage to drill successfully using a 3.5mm jobbie - was then tackled with a stud extractor. No foffing way was it going to move - it was a right barsteward. So I had to drill the hole (sic) thing out to 5mm and re-tap it. That was fine.

    So, nice idea, but I'm afraid a scewdriver won't have a cat-in-'ell's chance of moving it :(
     
  18. palavaman

    palavaman Well-Known Member

    Now, am I glad I found this thread;)

    Last year, I managed to do exactly what DA has done to my (sorry, our) grass cutter. It's a Ryobi or summat with the bit that ploughs as well. It cost £495 or so from B&Q. And after 6 months, I broke it. I had no idea the screw was wobbly till it snapped? It has been sitting in the garage ever since and the missus has been calling me a lot of names as a result?
    But now, following Handy,s advice, I'll try the 2mm cut with an angle grinder & take it on from there.

    Sorry for  BUTTING into your thread DA!! Ta
     
  19. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Yer, but not with an angle grinder. You want a slot, not a chasm.

    Mr. HandyAndy - Really
     
  20. Tembo11

    Tembo11 Member

    I suspect more like a cold chisel and a lump hammer to at least start.
    If the area is heated then the head ought to expand just slightly more than the bolt as it's both alloy that does so and just fractionally bigger and expansion due to heat is a function of the original size as well. This may help to reduce the stiction between bolt and head and perhaps liberal doses of a lubricant on the threads when it is hot to get some down the threads whilst the gap is larger

    Good Luck
     

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