Can someone explain
The best tool I've found to drill holes it sheet metal or exhaust tubing is called a "Unibit" Step Drill. You can find them in tool stores or online.
a drill. These are probably more expensive,
at least for one that'll last more than
one job. Another alternative is to drill
1/8", 1/4", 1/2" and then use a rotary
reamer to get the right size.

