What is the best way to cut a take-off hole in trunk lines?

[khe]

I am in the process of installing a humidifier and need to cut a 6" hole for the take-off adapter for the bypass duct. Would a Roto-Zip tool be the best or would compound offset snips be the best?

The Roto-Zip would get the job done but I'd be concerned with the shavings getting into the fins of the A/C coil.

The Snips would also work but would the left/right type be the ones to use or would the left/right offset type do a better job?

[NHMaster3015]

The roto zip will be a pain in the ***. I like offset snips, red handle because I'm right handed.

[plumberscrack]

The Roto Zip would be my LAST choice to cut sheet metal.

Red snips for me too :smile:

[khe]

Red snips it is! Menards has Wiss snips on sale for 30% off this week so I am going to pick up a left and right offset snips. I already have a set of straight snips.

Thanks for the feedback!

[NHMaster3015]

And a valuable and welcome addition to your tool box they will be. (pick up a pair of green handle ones while they're on sale, they come in handy once in a while)

[khe]

And a valuable and welcome addition to your tool box they will be. (pick up a pair of green handle ones while they're on sale, they come in handy once in a while)

I bought a pair of red handled and green handled offset Wiss snips and now have a complete set. I cut the hole in the duct in less than 5 minutes - what a difference the right tool makes. I like how the offset design keeps one's hands away from the metal.

Due to the location of the exhaust pipe and gas line, I did have to use the green handled snips to complete the cut.

The bypass duct is now all installed so all that is left to do is mount and wire the controller & outside temperature sensor and plumb in the water supply to the humidifier.

[Plumbfun]

Malco Tools makes a hole cutter specifically designed for cutting round holes from 2 to 12". If you are going to do alot of hole cutting its worth it.

[BHD]

I you can cut the entire circle either right or left will work nicely,

I made a set of templates out of sheet tin, use a marker and draw the circle or shape of the cut to be made,

use a flat screw driver and place on the inside of the opening, holding about 20 degrees off of square and hit with a hammer on it side, and let the edge of the driver cut the tin for a starting hole slot, take the snips and start to cut and work my way out to the drawn shape and follow the line around, until it is cut out, if there is not clearance I take the other snip and cut the other direction,
you can buy a cheap set of chinese made snips for fairly cheap and they will work for a few cuts, I keep a set in my truck for emergency cuts but if I had a lot of stuff to do I took my good snips,

Harbor Freight has a set for under $10
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=37325