Do these nuts need lock washers?

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For an exhaust system. It's a captive washer that is free to spin on the nut.

[Linked Image from fototime.com]
 
Given the length of those bolts, I would expect a couple of tensioning springs & washers would belong on the bolt-head side.
Usually see that arrangement near a down pipe to a catalytic converter.
 
If they came with them from the factory then Yes. They probably wouldn't have used them if it wasn't necessary.
 
Originally Posted by vw7674
Given the length of those bolts, I would expect a couple of tensioning springs & washers would belong on the bolt-head side.
Usually see that arrangement near a down pipe to a catalytic converter.


No, just the only pair of matching hardware I could find in my box of used nuts and bolts of the correct diameter. Between the two flanges and a gasket, there won't be all that much threads exposed after tightening the nuts.
 
Originally Posted by bullwinkle
Those are spring washers on those nuts, they will flatten out when tightened & act like a spring style lockwasher.

+1 They are a type of Belleville spring.
 
put some high temp loctite if you are worried. Those bolts will probable rust up and make their own loctite after a few temperature cycles anyway.

The point of a lockwasher is to bite into the stationary material and bite into the nut to keep it stationary as well. in this case the screw both the nut and screw head can rotate due to vibration so you would need to essentially lock the nut to the screw. You can use Jam nuts by tightening a second nut over the first one and torque it against tie flange nut.

If it came from the factory that way and wasn't loose when you disassembled it I wouldn't reengineer it.
 
Never use lock washers on exhaust parts. Use self locking nuts.
 
It seems like most (many ??) flanged nuts like those have "knurling" on the underside of the flange that provides some locking action. Can't tell from the picture if those do though.
 
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