Omni Dual Saw

I've used it. It's called the twincutter? Two carbide blades moving in opposite directions? Personally, I don't like it at all. It felt dangerous - and that's coming from someone with a lot of experience with powertools. Personally, I'd use a circular saw with an abrasive blade -- easier to control, easier to keep a straight line, and more predictable in how it's going to react. Just buy a couple more abrasive blades than you think you might need for good measure.

I would urge you to stay away from the circular saw as much as possible. When cutting, the edges become very hot, this causes the paint to release and in turn you will have rust in a short time about an inch up from the cut. Have you ever used the nibbler type sheers? You can buy a set or get an attachment for a drill at most big box stores, they work very well. The only problem you might have is crossing the ridges, but it is possible.

Have you asked your roof vendor to make the rips for you? Some of them are very accommodating.

webby3650 said:

I would urge you to stay away from the circular saw as much as possible. When cutting, the edges become very hot, this causes the paint to release and in turn you will have rust in a short time about an inch up from the cut. Have you ever used the nibbler type sheers? You can buy a set or get an attachment for a drill at most big box stores, they work very well. The only problem you might have is crossing the ridges, but it is possible.

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You may be able to rent a carbide-tipped metal-cutting circular saw. I haven't used them personally, but from what I understand, these cut much cooler, and also leave a mostly burr-free edge.

Here and here are examples of what I'm thinking of.

There are carbide tip saws for just your purpose designed to run on your skill saw. they are not inexpensive though. They work very well and avoid the sparks from the abrasive type.

Be careful using one of the metal blades on a skill saw, especially when cutting steel.... Unlike wood, the chips are conductive, (and the steel chips will follow magnetic fields like found in a motor) so if they get into the innards of the saw they can do some severe shorting out... It might be advisable to use a "throwaway" type saw (HF or big box low cost model) and / or try to seal up any cooling vents on the saw and use a short duty cycle on it while running the metal cutting blade...

My personal choice would probably be shears or a nibbler as previously suggested.

Gooserider

Check out http://www.metaldevil.com. I've been using their blades for a few years now. When I cut 1/4" thick 2" wide bar stock, I can grab the cut piece right after cutting with my bare hands. Just warm...never hot. These blades make short work of sheet metal. Great for demo/reclaimed lumber work, too.

See if your local rental shop has an electric metal shear or nibbler as we call it. It has a small jaw with a bladed edge on each side and "nibbles" its way through the metal, nipping about a 1/4" strip of metal away. you run the one edge along the line you mark to cut, and it does all the work, no heat, no danger. Make sure you leave an 1-1/2" or so extra along side the cut if you plan on bending the metal over the rake edge. Or you can bend it straight up and then fab a pc drip edge to hook over it and then go straight down along the side of the rake board. You may have to use a pair of tin snips here and there if the metal is corrugated. Get the proper tool for the job and save yourself big headaches &/or medical bills.

Peter SWNH said:

Check out http://www.metaldevil.com. I've been using their blades for a few years now. When I cut 1/4" thick 2" wide bar stock, I can grab the cut piece right after cutting with my bare hands. Just warm...never hot. These blades make short work of sheet metal. Great for demo/reclaimed lumber work, too.

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Where do you find them? Ever use them on asphalt roofing materials?