& thats why the exhaust manifold to exhaust pipe bolts on a car get easier to remove as the years pass=NOT!
Cylinder heads aren't stovepipe, exhaust manifold bolts aren't rivets and the threads of an exhaust manifold bolt are not exposed to the temperatures in a stove flue.
There is a reason for different types of fasteners whether you are cognizant of that fact or not.
Basically, you pop off like you know something and have no clue how ignorant you are. A fool really doesn't know he's a fool though so don't be offended.
You are unteachable and you got an anti-rep today.
However, since this is important and I fully realize there are people here that wish to learn, I will explain for them.
Inside a flue pipe, a horizontal cut of the cross section of flue pipe will reveal the temperature is not uniform in the pipe. The exhaust temperature is cooler at the outer edges of the pipe. This is what is known as a boundary layer. The boundary layer is dependent on surface finish of the pipe, but can be quite thin. It is a layer of turbulence which does not move as rapidly as the center portion of the pipe simply due to the friction between the flow and the wall of the pipe.
Putting a pipe together with sheet metal screws can cause the screw to penetrate the boundary layer and be exposed to gases much hotter than the wall of the pipe. Since the screw is metal and metal is a good heat conductor and the sheet metal screw has limited contact with the pipe, the sheet metal screw expands at a rate higher than the pipe because it does not have the surface area to conduct heat into the stove pipe.
The hot and expanding screw either 1) enlarges the hole in the pipe or 2) deforms the screw. Either way, when the pipe and screw cool down the sheet metal screw will no longer be tight in the hole. Repeated thermal cycling will compromise the screws ability to fasten the stove pipe together.
Rivets otoh may not stay tight, but will not compromise the stove pipe connection.
I graduated too. And learned how to spell.
