What kind of nut is this?

rickdm · 12-25-2005, 10:15 AM

In order to pass inspection I had to have a local shop take off my Ruff euro pre-muffler and put on a Cat. Now I want to get it off and put the Ruff back on. The Cat is held on by 13mm nuts that have the standard octagonal flats, but there is then a round smooth section which has a slot cut into it running perpendicular to the length of the bolt. These things start turning just fine (no rust or anything) and then after about a turn they get harder and harder to turn until they just freeze up, and it looks like they are mangling the bolt underneath. Are these some kind of special locking nut? Is there some trick to getting them off? Any suggestions for getting them off would be appreciated.

Thanks,
rickdm

svandamme · svandamme's Garage

what colour are they? copper like?

rickdm · 12-25-2005, 10:40 AM

They are a dark blue color.

rickdm

randywebb · 12-25-2005, 10:43 AM

I think that is a locking feature on the nut. It might be to prevent removal or something tho. I've seen them in a bronze coppery metal for exhaust before.

Jim Sims will know for sure and will no doubt see this eventually. Just have some nog and wait a while...

Wil Ferch · 12-25-2005, 10:52 AM

Hard to get a mental picture of this..."standard octagonal flats"...wouldn't that be "standard six-sided flats?"

A picture describing the rest of your text could make it easier for us to help, too... hard for me to see what you're trying to say....

- Wil

ANTONIO · 12-25-2005, 11:06 AM

Turn it out,turn it in ....a lots of times,use your favorite penetrant,good luck,cheers,Antonio.

911pcars · 12-25-2005, 11:09 AM

Sounds like a lock nut. Try holding the bolt head with another wrench while loosening. Use box-end wrenches to reduce the chance of rounding off the hex.

Sherwood

rickdm · 12-25-2005, 11:38 AM

Sorry, hexagonal. I am using a box end wrench on the bolt plus lubricant. This must be some sort of locking nut because it starts out so easily and then just locks up. I am going to be rather pissed at my mechanic if he put on some kind of tamper resistant nut to keep me from taking off the cat.

rickdm

911pcars · 12-25-2005, 11:44 AM

The lock nut could be backed up by bunged up threads on the bolt. Otherwise it's lefty-loosey, then remove.

Sherwood

Wil Ferch · 12-25-2005, 04:32 PM

Look at my earlier threads that say use a 5/16" stainless bolt...1.5" long under head, along wioth Silicon Bronze nuts...even has a a nearly identical bolt head that fits a 13 mm wrench of the original ( although it's 1/2").... do a search....

Wil

Flipseat · 12-25-2005, 04:41 PM

Sounds like a split & peened lock nut. Toyotas (and some others) use these stock on some exhaust parts. Thats just what comes to mind. Sometimes they come off fine, sometimes they don't. If its just a nut and bolt (and not a pressed in stud and bolt) then try to take it off. If it breaks, so what - it comes out that much faster. Put a new nut and bolt in when you replace the cat. If its a stud & nut then that makes things a little more difficult if you aren't familiar with replacing studs & FUBARed parts. Use a wrench on both end - preferrably the enclosed end.