How to drill out a broken stud.

[Pete.]

Here is how I tackling the 8 broken studs on my 1996 Bandit. Forget easy-outs and stud extractors for frozen-in bolts, you will veru likely only make things much worse.

There are a couple of tried and trusted ways to remove a stud that has some thread showing.

One way is to put a nut over the stud and weld the end with a mig welder getting it nice and hot, then un-doing the nut which should bring the stud with it. I don't have a mig welder - I have an arc welder but they are much harder to get good results with since the rod is fatter and for small diameter studs it's likely the arc will wander when you try to weld in the well of the nut.

The other way is to drill out the stud. This is no easy task, starting off on the end of a sheared stud is tricky and you must be dead centre to avoid having the drill wander off the bolt into the softer ally threads. This is how I have done it - by making a drill bushing.

First, take an old 12.5mm drill and chuck it up in the lathe backwards. Drill bits are not hardened at the shank so you can drill, file and cut them but they are made from hardenable steel which is what we want. Drill the tail-end 6.8-7mm which is tapping size for a M8 bolt.

https://peterrimmer.myby.co.uk/images/drillstud1.jpg

Then drill it deeper with a 4mm drill, which will be the pilot for drilling out the stud.

https://peterrimmer.myby.co.uk/images/drillstud2.jpg

Now I set up a M8 taper tap in the lathe using the centre to keep it perfectly in line.

https://peterrimmer.myby.co.uk/images/drillstud3.jpg

And follow it with a 2nd tap and plug tap to get the thread right to the bottom of the hole.

https://peterrimmer.myby.co.uk/images/drillstud4.jpg

https://peterrimmer.myby.co.uk/images/drillstud5.jpg

After that I part it off.

https://peterrimmer.myby.co.uk/images/drillstud6.jpg

Now I need to be avble to tighten this bushing, so I file two flats in it for a 10mm spanner.

https://peterrimmer.myby.co.uk/images/drillstud7.jpg

https://peterrimmer.myby.co.uk/images/drillstud8.jpg

Broken studs.

https://peterrimmer.myby.co.uk/images/drillstud9.jpg

Bushing fitted

https://peterrimmer.myby.co.uk/images/drillstud10.jpg

I used the drill rod so I could harden the bushing for use. This involves heating it up to cherry red and quenching. Here is what I did, but unfortunately I could not get it hot enough on my gas ring to lose it's magnetism (which is when it becomes hardenable) so it remained soft - so I used it anyway. Tomorrow I will take it to work and heat it with oxy-acetylene then it will be glass-hard.

https://peterrimmer.myby.co.uk/images/drillstud11.jpg

https://peterrimmer.myby.co.uk/images/drillstud12.jpg

As you see, the drill now takes a straight path directly dwn the middle of the stud.

https://peterrimmer.myby.co.uk/images/drillstud13.jpg

Drill extension for those hard-to-reach ones. Just a bit of mild steel rod, grind four small flats on the drill you use to drill the rod with then poke it in and give it a little squeeze in the vice.

https://peterrimmer.myby.co.uk/images/drillstud14.jpg

Holes drilled, spot on - only 6 more to go.

https://peterrimmer.myby.co.uk/images/drillstud15.jpg
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[neatbik]

Awesome.
Cheers Pete, i will remember that one.

[stonesie]

This makes me want a lathe, badly.

Top work

[binge]

Where is the Awesome rating when you need it!?!

Nice one Pete! I might need to bell you up about tapping soon. I need to tap 8 holes to M10x1.5, but ideally need the thread to go all the way to the back of the hole.





Ben

[Pete.]

[grahamd1]

Fantastic, now for us mere mortals without a lathe,

HOW MUCH MISTER ?

Gotta have one
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XV1100, XV750
CD175 (Rebuild)
CF70 (Chaly - Rebuild),

[nowhere.elysium]

That's a clever workaround. Nice documentation of the process Pete. Thanks for sharing it
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'10 SV650SF, '83 GS650GT (it lives!), Questionable DIY dash project, 3D Printer project, Lasercutter project

[Vincent]

That has got to be the easiest way to remove the studs if they've left a bit exposed - which they usually do, but if you don't have a lathe, and it's thick enough, you can sometimes get away with using the flange as a drill guide.
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Space Is Deep

[kestrel]

Nice well written post Pete. A set of these drill guides manufactured from a suitable material and induction hardened would be a useful addition to anyone's toolbox.
Perhaps you should contact a certain BCF member who has recently acquired a brand new CNC machine.
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Isle of Man.........Road Racing Capital Of The World

[kramdra]

This is good. I tryed mig welding mine, no good.

my CBR6 snapped 7 bloody studs. I found a local machinist and asked him to make me up one of these, he said it wouldnt work and id be ok doing it freehanded. So I invested in some TiN coated drills and carbide burrs (awesome). I tryed and buggered the first stud.

Decided to let shop do it, cost £800 included removing head, drilling out on machine and welding the buggered hole and putting it all back.

[TomGT]

I'd buy one, as would most of BCF I imagine
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1992 ZXR 400

[P.]

Easier option.

Sell.

[kestrel]

[P.]

Thanks

Great write up Pete

[Vincent]

Alternatively, use domed nuts on the studs, I've never had one exhaust stud fitted with a domed nut shear off.
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Space Is Deep

[Pete.]

Diod some more tonight. 6.5mm drill down the middle:

https://peterrimmer.myby.co.uk/images/drillstud16.jpg

https://peterrimmer.myby.co.uk/images/drillstud20.jpg

Too small as it leaves the thread intact, though it looks pretty cool. Tapping size is 6.8 but I wanted to allow a bit of extra clearance so I went for a 7mm drill. Tapped using a 1/4" socket extension backwards in the tap wrench to reach past the frame. You need a GOOD tap to do these:

https://peterrimmer.myby.co.uk/images/drillstud17.jpg

https://peterrimmer.myby.co.uk/images/drillstud18.jpg

Both done and bolts fitted:

https://peterrimmer.myby.co.uk/images/drillstud19.jpg

https://peterrimmer.myby.co.uk/images/drillstud21.jpg


Middle ones will have to wait until I get some more 4mm drills
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Raffles]

Will you be re-installing socket cap screws?
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A good loser will always be a loser.

[Pete.]

Yes, I'll be doing that. 16 years of rot hasfrozen them in and embrittled the bolts, I doubt the bike will be around in another 16.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Walloper]

Good idea and a good example to all BCFers on how to take a bloody photograph for illustration purposes.

A Tip for drilling Exhaust Studs.

They can get hardened form heat/cold cycling and normal bits don't last long when drilling.

I got this idea from an Engineer friend many hoons ago.

Take a masonry bit.
Grind a 'cutting' angle on the top of the tungsten carbide insert. (They are flat or rounded from the factory as they do not cut but impact and mash masonry)
They are very able to take massive abuse in service so are almost indestructible.

When sharpened they whiz through the hardest steel like a hot knife through butter.

If there is concern that the tip will wander then grind the wee bits of 'clearance' off the sides to the same diameter as the shank.

And lubricate.
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W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair