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Sheet Metal Products - Ductwork Demo

legacy - Feb 25, 2008 - 11:32 PM
Post subject: Ductwork Demo

We have a job that involves demoliting some very large duct that has had water dropping on it for many years now. The duct is 144" X 72" and is very rusted on the top and bottom panels. I believe it is all 18 gauge and the joints are Gov't lock. The duct must be cut into smaller panels to be reomoved from the mechanical room.

For past jobs we have always cut duct up with sawzalls. We have tried using hand held plasma, but it does not really work so well, we constantly have lost cut due to varying reasons. I purchased a small electric 12" Bosch abrahsive demo saw with hopes of safely speeding up the cutting process. Anyone have any other ideas for making the cutting process move faster?

jm413 - Feb 26, 2008 - 04:00 AM
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hey legacy, we bought a milwaukee 8" Metal Cutting Circular Saw, it actually works really well, youll definetly need some safety glasses and maybe even some long sleeves cause the little metal shavings can get hot. whoever you have using it you have to make sure works smart. i found that on heavier metal like, 1/4 inch, it can bind up and over heat sometimes also. you can see a picture of it on this website www.coastaltool.com if you have any other questions about it dont be afraid to ask, by the way the notcher still running like a champ Thanks

aramage - Feb 26, 2008 - 04:06 AM
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We always use a zipcut for that size of duct. We have a Bocsh grinder with zipcut disks. It makes a lot of sparks, and is loud, but does the job.

danski0224 - Feb 26, 2008 - 04:25 AM
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I would use electric double cuts for the bulk of it and cut the corners with a recip saw. A step bit would make a nice starter hole.

legacy - Feb 26, 2008 - 07:41 PM
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Thanks for the replies.

Those metal cutting saws look SCARY. Similar to the cold saw that we have in the shop for cutting ductmate. How long do the blades last?

I assume the zipcut discs are the very thin grinder wheels. I have used these before, but they seem to wear out after curtting about 5 or 6 feet of metal.

We wil be usuing the double cutters for some of the wide open flat areas to be cut.

I just bought 200 sawzall blades from one of those annoying telemarketers that call the shop. Bosch 4" 18 tpi for $1 a blade. Better than HD at least.

I'll let you know how it goes, were starting the job today.

locklin - Feb 26, 2008 - 11:48 PM
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I'm hoping this answer will help,but I'm not there. Take a set of Milwakee Double cuts and remove the biggest sections you can on each side,4 sides,tha take a portaband and cut the skelaton out,meaning pittsburgs, then open the govt. locks with a pair of u bangees made by vise grip, or a nail puller(flat about 1 1/4 inch wide. That should do it!