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[firemoth]

Hi. Changing back and middle sections of exhaust (2.2dti estate). The bolts bolting middle and cat section have both snapped. I've tried drilling them out (admittedly my drill isn't great) but it's hardly making a dent. Any other ideas?

Couple of pictures to give an idea





I've just put new section on for now but obviously not connected up

[tunnie]

Get better drill bits, been here on our V6's.

What makes it worse is when a drill bit snaps, then you have to drill that out 

[RobG]

Cobalt bits

[firemoth]

So I'm thinking along the right lines then

[Andy B]

So I'm thinking along the right lines then

Yes. Assuming a 2.2 uses M8 bolt the same as a V6, then you can either try drilling a tapping size for M8 ie 6.8mm (17/64'') and re-tap M8 or use a clearance drill ie 8.5mm & just use a nut & bolt. 

[terry paget]

It's tricky, so it's worth while trying to get the old bolts out whole, using lots of heat first, then much patience. Some still break off, so need drilling out. I've done a few. this is my technique. Others may know better.

First, buy some good new HSS or cobalt drills. I now buy packs of three (£1 ish) 1.5mm, 2mm 2.5mm, 3mm. File the broken off bolt flush with the pipe end, then centre punch a dent in the centre. Gently drill into the dent with the 1.5mm drill, oiling bit occasionally. When in 5mm or so, enlarge hole with 2mm, 2,5mm 3mm drills. Then use 1.5mm drill again to make more progress, again using other drills to enlarge the hole,and so on until you break through, but be careful as you do so that you do noit break the drill off. Once through, enlarge the hole with successive 0.5mm bigger drills until hole is big enough to accept bolt.

Make cuppa, tell wife how clever you are.

[firemoth]

Wife already thinks I'm a plonk. To be honest I'll probably just drill straight through dand nut / bolt it. Can't see any disadvantage from doing that (in fact I think it's better) then I don't have an issue if I decide to de cat at later date

[Nick W]

Are you drilling through from the back?

And are you trying to do the whole 8mm in one go? If so, swap to a 4mm bit, then the 8 or more likely 8.5/9mm bit to clear the remains of the stud. I  don't bother trying to rescue the tapped thread in such simple cases as it's rarely worth the effort.

Oh, and high quality branded, sharp drillbits are essential.

[biggriffin]

Wife already thinks I'm a plonk. To be honest I'll probably just drill straight through dand nut / bolt it. Can't see any disadvantage from doing that (in fact I think it's better) then I don't have an issue if I decide to de cat at later date

way to do it.

[ronnyd]

Try to get hold of some TiN coated drill bits, tougher than cobalt bits, but more expensive. 

[Andy B]

.....
Once through, enlarge the hole with successive 0.5mm bigger drills until hole is big enough to accept bolt.

 ....

Each to their own, but in my experience, going up a size as incremental as that is more likely to end up with the drill snagging ..... better for the drill to have something to cut.  I'd do it in one go 

[firemoth]

I agree with staging up, but only 2 sizes. 0.5mm probably a bit excessive unless trying to keep the thread. Which probably wouldn't work with me anyway. I'm going to see if I can utilise works workshop tomorrow. They do HGV repairs, I'm sure they can manage this

[Andy B]

..... They do HGV repairs, I'm sure they can manage this

I'm sure they can 

[Nick W]

I agree with staging up, but only 2 sizes. 0.5mm probably a bit excessive unless trying to keep the thread. Which probably wouldn't work with me anyway. I'm going to see if I can utilise works workshop tomorrow. They do HGV repairs, I'm sure they can manage this

In that case stop pissing about with drills, and use the oxy-acetylene. You heat the broken remains of the bolt to red hot, and puch it out with a drift and big hammer. Takes longer to move the welder to the job than it does to do.

[firemoth]

It's not a given they'll do it or even let my car in. I know I've got a quiet day tomorrow so will be sat in yard for a while. Going to give it the "can I borrow a bay and some tools" and hope they say "chuck it there, I'll get them out give me 2 minutes".