Cutting to the chase
No matter whether you regularly install ductwork or metal roofing, tools are probably a vital part of your work.
Choosing the right product depends on the specific application, the material being cut and to some extent, who's doing the cutting.
The following guidelines will help ensure that when contractors need to cut something on the jobsite, they have the right tool to get the job done. Special tools for forming sheet metal are also discussed.
There are two fundamental snip designs for cutting sheet metal: "tinners," which resemble scissors, and compound-leverage aviation snips. Each type is available in various cutting patterns and several blade styles.
Traditional tinner snips do a good job of cutting a variety of materials found at a jobsite, ranging from heavy, hard-to-cut materials such as sheet metal, to vinyl and aluminum siding, flooring, asphalt roofing shingles, gutters, flashing, metal roofing, canvas, carpet and other lightweight materials.
The decision of which type of tinner snips to use is based on the type of cut you need to make. Regular or straight-blade tinner snips cut straight and wide curves in sheet metal, while "duckbill" or circular tinner snips are easier to maneuver and cut tighter curves in sheet metal.
Tinner snips come in a variety of sizes - commonly 7-, 10- and 12-inch lengths, but they range in length from 7 to 16 inches. The larger sizes are capable of cutting heavier materials and have longer cut lengths.
Compound-leverage ‘aviation' snipsWhile traditional tinner snips have been in use for decades and still get the job done, "aviation" snips, which employ compound leverage, do everything a traditional tinner snip does, but require the operator to use less hand pressure.
Compound-leverage handles provide the power needed to cut heavy materials or make it easier to do a lot of cutting, while being much lighter and more maneuverable than traditional tinner snips. This is particularly true when cutting heavy metal such as 18-gauge sheet metal or multiple layers, while tinner snips capable of making the cut are large and heavy. Aviation snips can also reduce operator fatigue compared to using traditional tinner snips.
Aviation snips come in two general blade patterns: regular and offset. They are also available in "bulldog," long-cut and double-cut blade patterns. Regular- and offset-blade snips come in three cutting patterns, which are designated by grip color: red for left cut, green for right cut and yellow for straight cut.
The terminology can be confusing - Snips with red handles cut to the left, but are not for the left hand. In fact, a left-cut snip is best used in the right hand because it is much easier to cut across, rather than away, from your body.
Many sheet metal workers prefer offset aviation snips, while regular aviation snips are the most common type sold overall, since casual users such as homeowners and general contractors prefer them. Offsets are preferred because the blade design moves the material away from the blade as it cuts, making long cuts easier. Offset snips also cut tighter curves than regular aviation snips.
The offset design also offers extra safety, since they move the users' hand up above the material being cut.
‘Bulldogs'For cutting, notching or trimming very thick materials such as 16-gauge steel or cutting multiple layers of material such as seams or drive cleats, a bulldog snip is required (either a tinner or aviation snip bulldog).
Double-cut snips, which cut a curled strip of metal from the path, can be used to produce a very straight cut with clean edges in round pipe or duct. This makes joining pipe easier by avoiding ragged edges.
The replaceable-blade tinner snip is another very handy tool, which features lightweight handles and a long cut length. Available in various sizes, these are good for cutting a variety of materials and are much easier to use than a heavy forged-blade tinner snip. For example, they are easier to use when working from a roof or ladder because they are lightweight and easy to carry. But only lighter-weight sheet metal, such as 24 gauge, can be accommodated.
Cut length is also an important factor when choosing a tool. If a lot of extended straight cuts are needed, snips with a longer cut length, such as long straight aviation snips, replaceable-blade snips or larger tinner snips, are good choices. Longer blades cut thin materials, such as vinyl and aluminum siding, with fewer strokes, which makes a straighter cut, and with less chance of scarring the material when the snips "re-bite" on each cut.
Forming aidsIn addition to cutting metal, contractors sometimes need to form edges, folds or corners in ductwork, roof flashing and fascia. They also need to construct ductwork and join sections. There is a wide array of tools available to form - bend, flatten or straighten - sheet metal, ranging from powered or manual hand brakes, used in sheet metal shops and large on-site jobs, to specialized hand tools.
Among the most common hand tools are "seamers" and folding tools. Seamers come in various widths and with either straight or offset handles. Seamers typically feature compound-leverage action, which helps grip the material you're bending.
A traditional seamer tong is another option. It's often more durable and can withstand striking, since they have massive forged-steel jaws. Offset tongs provide added leverage.
Folding tools (available in 12-, 18- and 24-inch widths) can bend seams, normally either 1-inch wide (for joist panning, register boots or end caps) or 3/8-inch wide (to make drive cleats).
A variety of specialty tools are designed around common tasks for HVAC professionals. They include hand notchers, snap-lock punches, duct stretchers, hole cutters and crimpers.
Notchers make a "V" cut in sheet metal, while snap-lock punches raise a shaped projection in the metal, used to lock into the rolled edge of the sheet to be joined. Duct stretchers aid in joining two pieces of duct by pulling them together to drive-cleat installation. Crimpers come in models that make longer, shallower crimps to produce tight fittings, and those that make a deeper crimp for uses such as downspouts.
(This article was supplied by Midwest Tool and Cutlery Co., a Sturgis, Mich.-based maker of tools and other equipment.)