I am in the process of putting an exterior window in my attic space. The siding is aluminum and although most all of the cut edges will be covered with J channel flashing a small portion will be exposed. My question is which tool will allow me to make the cleanest, straightest cut. I have tried tin snips, skil saw and a sawzall (not exactly the cleanest). My thought was maybe a jigsaw with a metal blade, but I am worried about a reciprocating blade really screwing over the siding. Thoughts? Grinder with carbide or diamond blade?

Carbide tipped skill saw blade should do a good job. Remember, there will be some sort of sealant to cover the rough edges. So they should not show at all.

I agree with 450donn, and the finer the tooth the better.

Sorry guys I totally disagree with 450 donn and ballengerb1
I don't know what some sort of sealants is for putting J channel means or is for installing J channel. All new construction since siding came out never use any sealant on J channel or really anything it would defeat the no maintenance factor of what its biggest selling factor was and is. Sealants can fail in time
Feedandseed. To put your J channels in you don't need sealant
(I'm showing my age here now in construction)

The best and cheapest way to cut aluminum siding is the cheap very fine tooth plywood blade and they don't make those in carbide.

Put it in your skill saw backwards. It makes a VERY SMOOTH cut. This is how we did it back in the 70s and still do it today. It basically a cut/grind .

ANY tooth blade in the saw in the reg direction will tear up the siding, carbide or not and (Pull) out with its teeth and can make your saw want to jump around and possibly ruin your siding.

I'm the left over generation before vinyl generation but we still cut our aluminum soffits that way today. And every old siding for my chimneys and widows on rehab.
Feedandseed be sure to really concentrate on your widths for the finish opening of the J channel to the window edge/ brick bldg. and keep in mind the thickness of the actual metal and a tiny flare in the J channel.
Feedandseed I posted a tool you may need and it usually is at the big box stores is a Zip Tool and you made needs this in case a piece on siding Pops while putting in the Jchannel I tried to post the picture didn't work but here's the site and some good tips for you

http://www.rd.com/17738/article17738.html

Signed 21 Boat

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How about a roto-zip with a cutting blade. Seems easier that holding a circular saw to the side of a house.

Tgr

How about a roto-zip with a cutting blade. Seems easier that holding a circular saw to the side of a house.

tgr

Hi treed01 Welcome to AMHD... This is an old post. Happens all the time in the beginning.

Just on a side not a roto tip tool has no control for cutting siding. The Plywood blade back wards is still used to cut soffit and metal siding for J channel for new chimney which I did back in the 70s and still do it today not to mention how slow a roto zip would be...

Thanks for this tip of using the blade backwards. I will try it this evening. I was trying to cut aluminum siding away from my windows to install j-channel and 1x4 trim. The skillsaw with the aluminum cutting blade in the forward direction was making me nervous as it jumped around. 1st floor is going okay. I am just scared of doing this while on an extension ladder for the 2nd story.

If you are trying to cut the siding without taking it down and up on a ladder I suggest a multi-tool. It should cut the siding reasonably fast and you have a lot more control, only need one hand to cut.
You can pick up a corded version at Harbor Freight for a few dollars. Don't mess with Harbor Freight blades. Get a set of Bosh blades.

I think you will find the multi-tool a lot easier to handle up on the ladder than the skill saw.

Your cuts should be well within the accuracy needed for a cut covered by J channel.

I was thinking of using a grinder with a cutting blade. Mark a line and cut. Wouldn't that be easier?

I was thinking of using a grinder with a cutting blade. Mark a line and cut. Wouldn't that be easier?

Note this original post is 3 years old.

I see that this thread is a couple years old, hoping people are still here.

I have to cut a round duct for a range hood straight through the wall... through wood siding covered by lath and stucco covered by aluminum siding. Any suggestions?

I see that this thread is a couple years old, hoping people are still here.

I have to cut a round duct for a range hood straight through the wall...through wood siding covered by lath and stucco covered by aluminum siding. Any suggestions?

Draw a circle, bore a pilot hole on the circumference, use a medium tooth blade in a sawzall. Make sure blade is long enough to go through the wall. Going to be messy.