Cutting Sheetmetal With An Air-powered Nibbler

A nibbler takes nibbles(notchs) out of the SM, usally 1/4" wide x 3/32" long depending on how fast it's fed SM. We use them for heavy gauge SM, 14ga and up. A nibbler will feed it's self if balanced correct therfor can be hard to control when self feeding. Although it will cut circles it takes alot of experience to control. Following straight lines is no problem but that is the trade I served my apprenticeship in, sheet metal worker.

A Uni-Shear slits SM. Can be used upto 14ga. They make two sizes, one thats cutts upto 14ga and is larger in unit body, and one thats smaller in unit body that cuts too 18ga and is easier too control but best used with 20ga an under. Will cut circles easy and takes little practice to cut well. Will not feed it's self so very easy to control. If the blades are not adjusted correctly, gap adjusted, they will be hard too feed and a person will fight the cut. The uni-shear also has a balance point, to the rear of the handle, that when in balance cuts extreamly well as the balance causes the upper cut sheet too slip on the cutting head and binds when too forward. Single cutting blade.

Double Cuts is a shear that removes a continous strip of SM 1/4" wide. These are really nice as the will cut round pipe without being center split. Center split= long ways as in snap lock pipe joint before it's snaped together. Cutts larger circles very well and cutts duct work extreamly well. Has a little problem on tight round curves as in small diameter pipe or smaller round prestressed SM. Double cutting blade.

Hand Shears all single cut blade:
The bull shears or bull dog(sm slang) (Wiss W16, or Pexto Brand if you can find them) about 16" in overall length with 2.5" jaws and good for upto 20ga, 22ga if you want them to last 35yrs like mine. Great for hand slitting sheets, general fitting work and larger cutting circles.

Small bulls M5, size like left and right cut hand shears, good for upto 18ga small straight cutts as jaws are 3/4" cut depth. Wiss or Kline being the best brands.

Left M1 and Right M2 cut hand shears. As the name says one is for left hand cuts one for right hand. Again Wiss or Kline. Wiss was starting to become cheap made the last pair I bought 20yrs ago. I still use my orignal Wiss snips I bought new in 1969. Klines were just to expensive for an apprentice wage but looking back now they were not expensive.

T_Bone

Good things about nibblers.

Unlike a shear, it doesn't need to roll up one of the edges to get clearance and it doesn't tend to leave a sharp distorted edge. It will 'walk' into blind areas, and follow curves or complex cut lines easily.

Bad things.. bouncy and doesn't have any inherent tendency to cut straight. Like one of the other folks posted, you may need to clamp a straightedge to get a straight cut.

Another thought.. a GOOD metal-cutting saber saw with a fresh blade will do a remarkable job if the steel isn't too bouncy. Our sheetmetal shop had a purpose-built Bosch that was really good at jobs like you're describing. I often use my Milwaukee Sawsall for stuff like this.

Like most of the other folks here, I want to get a plasma cutter.. someday.

PS. Northern Tool has 'refurb' DeWalt cold-cutoff saws for $229.

Rod