Drilling high tensile bolts?

[predator]

Have a bit of a problem.

Took my cat converter off.. because I am installing catback.. snapped 3 of the 4 bolts due to being old unfortunately, and also very out of shape (heat I assume).

Now I went down and got what looked to be the most hardy drill bit available...a cobalt one, that was recommended for "high tensile steel, stainless steel, etc" (i.e. the heavy stuff).. $15 for one drill bit was a bit excessive, but I thought it would do the job so worth paying. But no luck Gave it a try and the thing is not even looking like it will drill through. Its pretty much as useless as the other "designed for wood, metal, etc" bit I tried. My drill is a fairly strong electric one, so I don't think the drill is the problem.

I assume the bolts in there are high tensile, and pretty tough, but there must be some way to get them out.

Any suggestions?? and no I doubt ezyout, etc will be strong enough to budge these, they are really fused in there. I think drilling is the only solution

You don't want to know how its all held together right now, but it is actually working

[51jay]

You don't mention what size bolts they were or what size drill bit you bought.

if the bolts were ...say...9mm diam I would start with a 3mm or 3.5mm drill bit and go through with that then enlargen the hole with a 6mm then finally 9mm. you need a fairly slow revving drill my preference being around 600 or 700rpm and lean on it as hard as you can without breaking the bit. High revs and not enough pressure you just produce heat and blunt the bit.

[predator]

9mm bolts.. and used 8mm bit.. I did try slow at first (drill does have adjustable speed), but that didn't seem to help. It has a handle, and applied whole body weight on it..snapped 3 cheapy bits that way, and they were the 2mm or so ones, but I was kind of getting angry at that point.

so that is probably the problem? sounds like I need to buy about 3 good drill bits at $10 a pop I could still be at it for 2 hours getting them all out bit by bit.

maybe i should just go bite the bullet and buy a new highflow cat instead.. less farking around!

[51jay]

It comes with practice mate bits shouldn't cost more than $3 or $4 for smaller sizes... check out your local Bunnings.....just DON'T get made in China. Ordinary high speed steel is good enough.

Idea is to put enough weight on so the bit bites in instead of just spinning.....a bit tricky with a 2mm bit

[predator]

ok, thanks for the advice.. will buy some new bits from bunnings and give it another try..

[CrAzY-BoY]

also try getting some cutting compound... that will help stop the bits getting blunt

[Bl4cK32]

and lean on it as hard as you can without breaking the bit.

Thats bs....its best to let the drill and drill bit do the work. Gentle pressure is ok, otherwise it could get ugly...ive seen some dodgy work practices in my time i tells ya....

Hows the new exhaust sound by the way? :uh-huh:

[GTRgeoff]

Pred, I use the suttons viper bits. Slowest speed and lightest pressure possible. Start wit 3-4 mm then the 8 should go through. Also consider an angle grinder and just remove the captured nuts, then use a nut and bolt to put it together as you can replace as necessary. Captured nuts on exhaust are just stupid.

[predator]

Viper are the bits I'm using.. I gave it another try on Sunday, and the small bits went through properly. Then the medium 4-6mm ones.. now its the large ones, and getting out to that final 9mm hole that is causing me the grief. Saturday morning, its time to buy some new larger bits (think the others are blunt now) and I think I can finish the job 3rd time lucky

Angle grinder was used to remove the outlying pieces already

Its not worth spending the time that I am spending on it, but I think I will get there thanks to all the advice!

Hows the new exhaust sound by the way?

errrr, kind of loud as its held together by one proper bolt and 3x g-clamps, as I *had* to get it together to get around to work.. yes, very dodgy.

[GTRgeoff]

Pics or Ban mate

[someonestolecc]

I love these kind of threads

Good luck with your zorst I know how sometimes the smallest things can often take the most time and cause the most frustration - but then reward

[predator]

Well its fun to read ...painful to have do when you're in the position!

anyhow, tonight, after a lot of stuffing around, finally got them all out. Got a couple of new shiny bits. Found that the bigger bits don't actually "cut" that well into the metal.. I think its just because the tip is not really designed to cut in itself. I actually found that using the skinnier ones I kind of rotate the drill in circles to cut through a bit better. So I was cutting into the sides of the hole, rather than directly down. Could just be my drill, I don't know. But it got there.

Anyhow, got some some high tensile bolts, and can fit her back up in the morning. What a stuff around though! Boring obligatory pick attached

Pics or Ban mate

lol. unfortunately it was dark when I got home so didn't take a photo before I pulled it off. G-clamps don't work the best though to give it a great seal, as it was squirting out carbon all over them Better than no exhaust at, but only marginally! It did hold up for 3 days without falling off though, so they did enough.

[predator]

All done! Happy with the final sound of the exhaust too, nice and quiet during everyday driving, with a good sound (but not massively loud) when you step on it Looks nice too. Just what I was after.

Nice and professional in the end.. got a couple of new gaskets too to give a nice and tight seal. If anybody is interested, the ones for a standard cat are ACL JE931 (can buy from Repco for $4 each)

[GTRgeoff]

Good one mate. Was hoping to see the clamping effort too.

Looking at the first pic.....Oh the butchery

[Bl4cK32]

glad your happy Exhaust done me well in the time i owned it, good to see it went to a loving home