exhaust nuts

[g zero]

Looking for 5/16 -18 nuts for the exhaust flanges . The std type use a 1/2 wrench , I am looking for ones that use a 7/16. Seems that the high temp lock nuts that Air Spuce sells are fine thread.

Thanks. Merry Christmas.
Tom

[rocketbob]

Grade 8 nuts from your favorite home supply place work fine, with a star lockwasher and a flat washer to keep the flange from being nicked by the star lockwasher. I use nickel antiseize on the threads, goop up both sides of the blo-proof gasket with red RTV. Don't torque blo-proof gaskets unless you're absolutely certain you will not take them off, they are not supposed to be reusable.

[yakdriver]

Aeroinstock has them. They are stainless and use a star washer so you can get them off when you have to. Don't use the self locking nuts as you might not get them back off.

[g zero]

I took a 1/4 20 grade 8 nut drilled it out with a F bit on the lathe and taped a 5/16 18 thread . Looks like it should work just fine.

[fehdxl]

Originally Posted by rocketbob

a star lockwasher and a flat washer

I don't understand this? The star-washer's teeth are supposed to bite into the nut and something non-rotatable (is that a word?) so that the nut won't vibrate/heat-cycle loose, right? If you put a flat-washer between the star-washer and the flange, what's keeping the flat-washer-star-washer-nut assembly from rotating along the flange?

Just seems to me that the flat-washer is defeating the purpose of a having a star-washer in the first place.

Thanks!

-Jim

[fehdxl]

...and to further confuse me, just after replying below, I looked at AC43.13B and it says this:

7-87. LOCKWASHERS (AN935 AND
AN936). Lock washers may be used with machine
screws or bolts whenever the selflocking
or castellated type nut is not applicable.
Do not use lock washers where frequent
removal is required, in areas subject to corrosion,
or in areas exposed to airflow. Use a
plain washer between the lock washer and
material to prevent gouging the surface of the
metal.

So I still don't get it?

Thanks!

-Jim

[Guy Prevost]

Originally Posted by fehdxl

...and to further confuse me, just after replying below, I looked at AC43.13B and it says this:

7-87. LOCKWASHERS (AN935 AND
AN936). Lock washers may be used with machine
screws or bolts whenever the selflocking
or castellated type nut is not applicable.
Do not use lock washers where frequent
removal is required, in areas subject to corrosion,
or in areas exposed to airflow. Use a
plain washer between the lock washer and
material to prevent gouging the surface of the
metal.

So I still don't get it?

Thanks!

-Jim

The lock washer maintains joint preload (to a certain extent). That way when the nut loosens a small amount, it's not free to rotate off the rest of the way. It still has the friction generated by the lock washer. You use a flat washer under the lock washer so as not to tear up the expensive parts underneath.

[noelf]

...posted a "Hints for Home Builders" video on just this subject, including exhaust gaskets, nuts, washers and lock washers, how and when to use them and how to torque.

Last weeks video was on how to care for the spark plug copper gasket.