On Sun, 6 Jul 2003 07:54:16 -0400, "Joe Odom"
wrote:

I need to replace the vent pipes for my hot water heater and furnace-
they're 3", 4" and 6"diameter and made of sheet metal. The duct assembly is
held together with short sheet metal screws-- and I'm not sure how to start
the screws in the new vent system.

I always thought sheet metal screws were self-tapping but doesn't seem like
you could push very hard to self-tap without bending or crushing the pipe-
especially the large diameter ones. Do I need to drill a pilot hole or what?

Joe

You need a pilot hole. Pop rivets work well too.