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harlequin
03-02-2007, 09:26 PM
was drilling out broken 8mm bolt from block of motor could feel it breaking through then drill broke F&%#@* below surface of bolt tried to gently break it up & remove pieces unsuccessfully . do not have access to edm so have heard of using either alum or nitric acid to slowly dissolve the bolt time is now on my side, any one ever done this i havent any advice would be cherished thanx andy

Roughasguts
03-02-2007, 09:32 PM
Hmmm interesting you got a Die grinder like a dremmel and start grinding the bit out.

blu
03-02-2007, 09:55 PM
I'm with Roughasguts use a dremmel with a steady hand

snelly1971
03-02-2007, 10:06 PM
Do what i would do....grab a BIG BLOODY hammer and smash it.....Sorry Andy ....but thats what i would do in temper...shit like that really pisses me off.....best of luck

Stuart
03-02-2007, 10:23 PM
Drill out and insert the largest helycoil you can, then screw in the largest bolt you can and wind out slowly.

Stu

finga
04-02-2007, 05:11 AM
Don't use the acid.
Persist with the breaking of the drill or good old dremel.
I've worked and worked and worked on broken drills and eventually they come loose and pull out without further adieu and sometimes they come loose by working a narrow scribe down the flutes and working, working, working them out whilst trying to unscrew them out of the hole.
But still a bugger of a job no matter which way.
How big a drill bit is it in the 8mm bolt??
If you only used a 3mm drill there maybe room to drill another hole next to it and work form there. That usually means a helicoil is going to have to be used in the block though.

Roughasguts
04-02-2007, 07:58 AM
Heres another thought, don't like it's chances but sometimes you get lucky.

Get two jewelers screw drivers, and stick them as far down between the drill bit flutes as you can. Then get a bigger screw driver and stick the shaft between the two smaller screw driver shafts.

Use the large screw driver at 90 degres flat to the busted bit and give it a turn in both direction. If you can turn it a fraction it might just jump out.
Or proceed with screwing it out.

Grand_Marlin
04-02-2007, 08:00 AM
I'm with Snelly......

FNQCairns
04-02-2007, 08:17 AM
I know how you feel just yesterday I finished drilling and taping a couple of 8mm bolt threads into my o/Bs midsection after the bolts broke, 8mm bolts seem to have that habit.
How much meat (metal) is there around the bolt hole? You may be able to consider doing as I did and get rough with it, then get the hole welded up, a welder in my experience can get a good result.
Saves lots of brains surgery sweat!

Apart from that Gut's idea of patience and fiddling will pay of.

Use only quality drill bit's some of the stuff they sell these days is rubbish.

good luck fnq

cheers fnq

Roughasguts
04-02-2007, 09:34 AM
Yep FNQ is right the drill bits are a major player in this, On me last busted bolt I bought one of the titanium drill sets from super cheap with .5 mm steps in sizes. It took bloody ages to drill out the S/S yes 8mm Bolt, but got it eventually, with a new bit every size up, it shouldn't jam.
Also the bit needs to be as short as possible to reduce the flex and light drilling pressure.

Use plenty of WD 40 with the extension tube on it to keep washing out the hole as you go.

Then when it's time to tap a new thread put the tap in a battery powered drill, run it in till it slows pull it out, wash and lube run it in till it slows again it will take a few minutes, but the result is a nice straight even thread.

It's a bastard but if you pull some beers out the fridge as you go it gets better.

blaze
04-02-2007, 09:45 AM
used all ideas given so far (eveen the big hammer) one method I have used as a last resort is a oxy welding flame with the smallest welding tip, heat the end of the broken drill untill red and then carefully over oxodise the flame by turning up the oxy control knob this will then act as a mini cutting lance. Be extremely care because otherwise you just as well went with the big hammer and by passed this last resort.
cheers
blaze

Roughasguts
04-02-2007, 10:19 AM
Try this next time Blaze, I like making things and have all the gear to do it so it's pretty easy for me.
I might go and snap a drill bit and make this up and see if it works.

But thinking if you got a flat 8mm x 3 mm By 40mm long steel plate and run your angle grinder cutting disk down the guts of it say 10 mm, So it has a slot in the middle, That slot will go between the flutes of the broken drill bit.

Now get some 13mm steel rod and weld that to the other end so you have a T' Handle.

Then grind a round edge of each side of the steel plate, so it's around 7mm and won't jam in the hole.

Wack the gadget in the hole between the flutes of the drill bit, tap it in with a hammer, then give it a good twist.

Either you will keep snapping the drill bit or the bit will fall straight out.

Mr__Bean
04-02-2007, 12:18 PM
Not sure how much you value your engine block, but to me each of the suggestions has a fair degree of further risk assosciated.

Are you able to take it to a toolroom with a portable EDM?

These things always get worse and worse as the first concepts fail.

I have had very limited success once the drill fractures and splinters into the softer parent metal.

I have heard of guys using the old fashioned EDM hollow lances in their home welders with the water running down the centre of the lance. This would be my last attempt before taking it to be burnt out with an EDM.

- Darren

i wish
04-02-2007, 12:36 PM
ok heres my 2 bobs worth disconnect battery remove all fuses, find a nut thats fits over( sligthly bigger than bolt )and using either a mig or stick welder weld the nut onto the bolt,allow too cool,with a good fitting spanner slightly do the bolt up this will break the seal on the thread then undo bolt slowly (bout 1/4 a turn at a time and just like tapping a thread go back the other way0then undo again and so on until the bolt is out trust me this works have done it a thousand times ps weld the inside of the nut onto bolt ive used this proceedure on farming equipment for the last 10 yrs in my trade as a welder anyway good luck will be reading thread to find out how u got on

i wish
04-02-2007, 12:51 PM
forgot to tell u this proceedure will remove the bolt and drill in 1 go nut might break off on drill bit but keep going just fit another nut onto bolt so u will end up with the origonal thread been intact the only reason the nut will come off is because of the differnt metal structure (drill bit high carbon and brittle) keep away from heli coils and die grinders on a job like this ,when u fit ur new head stud coat it with anti seize this will make sure it will come out next time and do your other studs or bolts too ,preventative maintance you cant beat it

Roughasguts
04-02-2007, 01:19 PM
Mate that would work I have done it. The only problem with a stick weld is the aluminim block. That will melt and blow a bloody big hole in it before the welding of the nut on the stud takes place.

Just one of tha many mistakes I have made.
But it was on a lawn mower so couldn't give a rats arse about it.

harlequin
04-02-2007, 05:35 PM
well had a go at it today the original drill that broke was 2mm dead centre so went round the outside with 2 & 3 mm and the dremel with 1 diamond bit one silicon carbide bit ended up destroying them both but got it all out in 5hrs what an ordeal dont ever wanna do tha again the other 3 bolts broken in the block were removed successfully after buying some quality drill bits and going in 6mm with 2mm bit then giong in 4mm with 5mm bit in a stepped fashion so as to leave a detent for the 2mm bit to follow but relieving any excess prassure on it this is what i should have done to the first one. but thats hinsight wanna thank every one for their advice as it all helped the acid wouldnt have worked because marine ally has 5% magnesium and nitric would attack it apparently it may work with some of the other series ally.will make sure it is all put together with plenty of grease & will be stripped down yearly so it will not happen again am going to see if there is a chromate conversion coating or etch primer to recoat hte corroded surface inside of the head water cover exhaust cover where the coorsion occured so thanx again all advice is of value and appreciated gonna have some beers now

tigermullet
04-02-2007, 06:58 PM
And boy o boy have you earned one. Great work!

rick k
06-02-2007, 10:58 PM
Harlequin, well done, what a job! And others, fascinating read.

A mate likes to use left handed bits (P&N, probably others) to drill out broken bolts/studs. Claims they often come out while drilling the holes.
Never seen it done, could be BS (not the left handed bits, seen them), but despite being a fisherman he is usually reliable on non fishing related issues.

I broke a stud removing the head from my old mq, with a few feet of water pipe and a good 10mm hex head key. The iron block allowed the luxury of oxy to heat the remains, which had the good manners (or design)not to snap off flush. Came out nice and easy then. I hate torqueing down those stretchy head bolts. Nerve wracking.

Reef_fisher
08-02-2007, 08:00 PM
Well done mate, now use antisieze before anything goes back in. Never ever use helicoils on any thing like head bolts, you may get lucky , but helicoils are only good for 75-80% of the original strength of the original hole.

Roughasguts
08-02-2007, 08:40 PM
Helicoils, never used one.

But I do wonder about the strengh of a re tapped thread, under close examination they aren't particually as sound looking as the original thread you would see.

Spaniard_King
09-02-2007, 05:20 PM
Dynamite may work as well

:P

Eagle
09-02-2007, 06:14 PM
It's impossible to drill a drill bit out with another drill made from the same material which in nearly every case is High Speed Steel. The Titanium drills, the gold coloured ones, are still High Speed Steel. The Titanium is just a coating on the surface and only serves to alow the chipps to slide up the shank more easily as the Titanium has a very low coeficient of friction. It WILL help the cutting edge to penetrate into the steel because it is a bit harder than the material the drill is made from. The reason the drills jamb and break is that the cutting edges have too much clearance and will dig in fiercely when breaking thru. If the clearance is reduced by careful (?) grinding, the drill will still work with the properties of a fully coated drill. To reduce the clearance you MUST know how to correctly sharpen a drill to enable the geometry to be changed to suit the occasion. Not an easy task for a non-tradesman and can be difficult even if you are. If you use a Tungesten Carbide drill you would be VERY lucky to get the drill to cut where you want it too as it will run off into the softer steel, ie, the bolt.
A realy great way is to use the dremel or similar high speed tool but dont use a small grinding wheel. Use a 3.25mm diameter DIAMOND coated cutter (or a size to suit). These "cutters" are actually a grinding "wheel" in the form of a straight rod. The diamond grit covers the rod for about half its length and the smooth end goes into the Dremel chuck. These "cutters" come in diferent diameters and shapes and will cut faster and easier than any conventional standard grinding wheel. Those that have diamond grit on the end will alow you to penetrate into the material but the diamond will quickly dissapear, Use the side of the cutters. They will fly through High Speed Steel but must be run at mediun to high speed and use a lubricant/coolant. WD40 or similar or water soluable oil will work very well. I would use the water soluable oil as a first go becaue it will cool the cutter faster. Dont drive the cutter too hard but let it cut at its own speed, ie, dont press too hard. If you use too high a rev setting, you may knock all the diamond grit off the shaft. You will soon find the ideal setting. The diamond cutters WILL work and they do a fantastic job. You should be able to find them Super Cheap or a similar supplier.
Good luck, patience and diamond cutters will work wonders.
Eagle

harlequin
09-02-2007, 10:18 PM
yeah had a set of recoils on hand just in case but really didnt want any more dissimilar metals and after reading fnq response if it happens again i will get rough then weld it up retap it, but it wont happen again i will do more regular maintenance. you quite right in what you say there eagle these second set of drills were cobalt and web thinned or split point have a shallower cutting angle and less clearance/relief angle these work a treat but still need upmost care. my head bolts, its a yam 90hp are steel and have a heavy chrome coating very magnetic positive they arent ss. i will take the crappy drills in to work and do some hardness readings on them as well as some better quality hss and titanium coated, also want to take some of me plate ally in 5086 beat shallow dishes in it put in some broken drill and bolt left over from head put some nitric in and see how much it eats both and ally away. at the moment i am trying to get hold of alodine 5l cost $86 from where you guys are brissy but because its dangerous goods it will cost $170 to freight it here sa. cant source it here any where when you tell em its hexavalent chromium they think the film erin brokovich and freak. i have sand blasted the head and covers will alumiprep it then alodine it then final coat either heat resistant epoxy or blackcote por15 product need to arrest the corrosion as much as possible as the anodised surface has been detroyed by corrosion both galvanic and electrolosis so i wont be on the water for a week or two. bye all andy

BilgeBoy
09-02-2007, 10:32 PM
Tea Tree Oil...if you have time. This is a great tip for all of you who may be restoring older stuff. I have used this for years in the mechanical trade and it works great where dissimilar metals that have reacted. Especially old Truimph stag heads....when the steel bolt has corroded and swollen into the alloy head. We would just poor on the Tea Tree Oil...and let it do its thing. Can take days, but it somehow wicks its way and breaks the bond...Magical stuff!!!

Not real good if you want to go fishin same day....but a tip none the less!!

Roughasguts
10-02-2007, 08:14 AM
Interesting tip there Bilge boy, will keep that in mind for next time I play with seized bolts.

Something I got can be plenty of time, no hurry to do nuthen lately.

harlequin
10-02-2007, 01:25 PM
never knew that bilgeboy use to cut & distill that stuff when i lived in bungawalbyn south of coraki amazing shit, killed leaches and affected the anticoagulant stopped the bleeding killed fleas on dogs stopped fungi growths but dont put it on ya private bits without being diluted. will certainly remember that tip thanx

tigermullet
10-02-2007, 03:04 PM
Tea Tree Oil...if you have time. This is a great tip for all of you who may be restoring older stuff. I have used this for years in the mechanical trade and it works great where dissimilar metals that have reacted. Especially old Truimph stag heads....when the steel bolt has corroded and swollen into the alloy head. We would just poor on the Tea Tree Oil...and let it do its thing. Can take days, but it somehow wicks its way and breaks the bond...Magical stuff!!!

Not real good if you want to go fishin same day....but a tip none the less!!


Thanks a million for that tip. It might be just what I am looking for. The aluminium cabin door on the boat is almost seized around the hinge pins.

The hinges are aluminium and the pins are stainless steel. It would be a real bitch to drive out the old pins. I was thinking of drilling a couple of holes through the hinges until the stainless steel pin was hit and then trying to squirt in deagreaser or some other substance and then follow up with lanolin spray.

Do you reckon that Tea Tree Oil would work on that combination of aluminium and stainless steel if I can inject enough with a hypodermic syringe?

BilgeBoy
17-02-2007, 11:28 AM
It would be worth a try tigermullet...have never tried it with stainless myself so I would be interested to hear how you get on. We would hang the engine in the air by the head with a tyre under the sump...and in about 2-3 days the engine would drop away from the head.

BilgeBoy

1975fflh
17-02-2007, 01:56 PM
Hi
Ever heard of an easyout, you drill a small hole and insert the easy out it is really a tapered reverse thread tapered bolt you screw them in anti clockwise and as the bite it will twist out the old bols or drill bit they come in different sizes, i bought mine years ago from a discount tool store in wollongong, they used to be common, I bet bunnings has them or gasweld, I have used them on all sorts of motors and bikes over the years, sometimes you have to swing on the and think they are going to break but they are high tensile.

They should only cost about $20.00 for a good set.