Exhaust bolts stuck

[J4CKO]

Any suggestions, am just replacing the exhaust on my 350Z, the mid section to Y pipe wouldnt come apart so I used a cutting disk to but the bolts off, I need now to drill out the remainder of the studs but I keep nailing drill bits, whats the secret ?

[cornet]

Only drilled out a few bolts in my time however the tips I was given were:

• Use good quality drill bits (I have some cobalt tipped ones that have served me well)
• Use a centre punch so the drill doesn't wander
• Drill to slowest setting
• Apply enough pressure so it cuts but don't apply too much more after that

I suspect some of the above is wrong but has worked for me in the past.

[J4CKO]

Yeah, think you a are right, my drills are either a weedy battery one or a mains one with zero control, might nip to get some decent bits and a new cordless tomorrow.

[cornet]

I suspect a mains one with speed control is going to provide the most torque.

I've got Makita 18V cordless one and managed to drill out a few bolts, do have to keep stopping to let it cool down though.

[dblack1]

There isn't much in the way of info here... Did you try penetrating oil? Why do you need to drill it out? Did you not cut the end of the bolt all the way off? I've always used penetrating oil and heat (torch, heat gun, run the car and let it heat up the exhaust) to help loosen up bolts on the exhaust.

[CrutyRammers]

Decent HSS drill bits should go through studs with no problems, as long as they're not blunted.
Use a small size first to drill a pilot hole (3mm or similar), then a larger one to take the bulk of the stud out.
If any of the stud is still protruding, you might be better off with mole grips and plusgas, rather than drilling though.

[J4CKO]

Im fitting an aftermarket exhaust as mine had sheared at the flange between the back box and mid section, this is the studs that attach the front "Y" pipe to the rest of the exhaust, the studs seem to be hardened in some way (welded in, exhaust heat ?) as my normal methods arent working, I have though managed to get through one of the buggers and now can concentrate on the other one, am just using HSS bits, was using WD40 but am trying 3 in 1 oil and only doing a few turns and stopping, seems to be getting through but its the lack of space and awkward angle that isnt helping, still reckon another half hour my do it and I can then hear my fruity new exhaust which was cheaper than the original by a third, plus seems better quality being Stainless.

[Petrolhead_Rich]

J4CKO said:

Any suggestions, am just replacing the exhaust on my 350Z, the mid section to Y pipe wouldnt come apart so I used a cutting disk to but the bolts off, I need now to drill out the remainder of the studs but I keep nailing drill bits, whats the secret ?

good drill bits, cutting fluid (to cool the drill bit), slow and with a good amount of pressure on the drill.

oh and patience!