Another vote for tin snips. Quiet, safe and accurate (once you get the hang of it).
I ended up with good ones from a the Snap-On truck that used to stop by the place I worked, when I was doing custom car audio installations a million years ago. If nobody here offers any specific brand names for "good ones", Snap-On is a safe bet.
I guess tin snips it is, since that's the unanimous view. I didn't even try them because I thought that would never work, but obviously I was mistaken.
Thanks every>> I need to cut 2 rectangular openings in an existing HVAC supply and >> return
Make sure to get the ones with the right color handles.
There are three different types with a corresponding handle color (I don't know what color goes with what). One that cuts in a clock wise motion one that cuts in a counter clock wise direction and one that cut straight. Pick the one that works the best based upon the circumstances.
Instead of tin snips ask for aviation snips. There are 3 types, one that cuts to the right, one cuts left and one cuts stright. The handles are usually color coded as to which way they cut.
I have always called that particular tool "Aviation Snips". I thought tin snips were the ones that look like heavy duty scissors. In a pinch I have used BX cutters on sheet metal and they worked well except the handles are shorter. Consequently you get less leverage with them.
Get a one inch hole saw and drill the corners out with it. Use tin snips to cut the straight lines and finish by squaring the corners with the snips. I've done this several times.
The hole saw will be dull after a few holes so dont expect to use it fir your fine furniture later.
the nice fellow had a metal tool with a V shape opening, he drilled a hole in each corner, then put the v tool in and hammered it, cutting the metal, FAST and easy, the rough edge was totally covered by the humidifier, so appearance didnt matter
For some reason, I was thinking that there would be no easy way to get tin snips into the metal and cut along the line without mangling the metal. Then I watched the video and -- DUH -- I realized that I could just make the first entry cut in the middle of the area to be removed, and then approach the actual cut line from an angle and do the cutting from there. I am not usually this dense.
Hand tool to use is sometimes called Aviation snips, or Aircraft snips. Has mechanical advantage to make cutting metal much easier. Don't get the long jaws tool. Will easily handle most duct work steel.
May leave the metal rough and edges rough. Go to Automotive store, or sears, and get auto body and fender work tools, and there are small hand held anvils, called 'dolly blocks,' IIRC. A set of body work tools may out of your price range.
Just went up to Sears, (which in this rare case the craftsman tool might be OK.) they look like are starting the holiday sales with a set of aviation snips for a reasonable price. If you go to Sears, stick with craftsman line on this. Looks like cost will be reasonable come November. Most BORGs carry aviation snips. I like brands: Wiss and Stanley. Have used Klein, seemed OK.
I make a hole in the middle of the drawn out rectangle then cut an X out to each corner, trim the end tips off the 4 "pie shaped" triangles, then fold them over into the duct to create a reinforced edge and crimp the fold with Robogrip pliers all along the way. The doubled up edge gives more material for the sheet metal screws to grab into when you are eventually screwing on the trim grate and makes the hole edge very strong and rigid. I'm not a sheet metal worker, maybe others know better, but the few holes I've made came out pretty good.
The HVAC crew that installed my new furnace last week did as others have described here. Used a hammered cutter to make a simple slit in the sheet metal, then used offset tin snips (they'll save your hands a lot of cuts) to make the rectangular opening.
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