1. Aviation tin snips will do most anything you could imagine. A bit of a learning curve, and the cuts may need some subsequent file work.

2. A pilot guided,flush trim, carbide tipped two or three flute router bit will work in a router or better, an air die grinder. Smooth, though slight scalloping may be seen on edges, depending on skill of operator. DO NOT use these on steel!

3. 1/4" shank carbide burrs work very well in a die grinder. They eat steel.

I don't have the time to type out 15 pages of why this is potentially hazardous. You realize anything sharp could cut you, anything rotating has its own dangers, you shouldn't run with scissors, it WILL put your eye out! tiny sharp copper swarf will fly everywhere with rotating tools ( which is why air powered is superior here, no motor armature, brushes etc.) If you don't clean up or contain, the chips will be EVERYWHERE.

Different snips and a collection of files could do all you want at a peaceful quiet pace.

I will try snips and files. Bondo is on hand for errors in the second project. Thanks for the safety warnings. I will also get a metalworking kit for my Dremel and a pair of safety goggles for the first project.

Many thanks.

I routinely do fairly intricate cuts in galvanized steel sheet metal in gauges ranging from 20ga (0.0396") to 8ga (0.1681") and as Alphonse said earlier, my primary tools of choice are aviation snips.

Having said that, it must be noted that not all aviation snips are created equal, and you can expect to get what you pay for.

In the sheet metal trade the aviation snips of choice are made by "WISS". You can expect to pay about $15 to $20 for each snip but they are well worth the cost.

When examining aviation snips you will note that there are three colors on the handles, RED, GREEN & YELLOW.

Red snips are properly called "Left Hand snips" because they are designed to cut straight or a curve to the left.

Green Snips are properly called "Right Hand snips" because they will cut a straight line or a curve to the right.

Yellow snips cut a straight line.

If you are right handed you will find the RED's (left hand snips) to be the tool you use most often because it keeps your guideline on the left side of your hand where it is easier to see. (If your left handed the Green's would be easier to work with).

When working on ductwork we often have to cut through a folded seam that may be as much as 4 layers of the sheet metal. In this case we use a pair of "Bulldogs" which look like a pair of Red's with short stubby jaws.

The real secret to quality cuts is a fine layout line. Traditionally a metal scribe or Scratch awl is used to
mark your layout line by making a fine scratch on the metal.

Generally in the trade we don't use the Yellow snips much because both the Red's & Green's will cut a straight line.

A nice precis on snips, that.

As far as the smoking fireplace, that sounds like your house is too tight and the smoke is rolling out. Try cracking a window while burning and see if that stops the problem. If so you may want to consider installing an outside air intake for yout fireplace.
Dave