Achieve good sheet cut

Apr 03, 2024

Shears are best suited for very thin sheet metal, like a 22 or 25 ga., requiring any long, straight, and fine-line cuts. Metabo

Fabricators working with sheet metal know that some projects often include cut-outs, and in many cases precision is key. There are various hand and power tools available to help fabricators achieve this goal. Material thickness and type as well as cut-out size and shape will help to determine what tool works best.

The thickness of material to be cut is an important factor. Most power tools for this work can handle material thicknesses from 22 to 6 ga. (0.7 to 5 mm).

Is the cut-out small? Does it require tight turns? How can you cut the hole to start the cut-out? Is the cut-out big enough to drill a hole to put the head of the power tool through? Are there a lot of straight-line cuts? These are just a few questions that will help to determine the best tool for the job.

Some experienced fabricators may know exactly what they need or have a preference from one tool to another. However, for those that are inexperienced or looking for guidance, power tool manufacturers can help suggest which option might work best.

While most tools available can be very precise when it comes to cutting, much of the precision is based on operator skill. A power tool is only as good as the operator, but having the best tool for the job is a good place to start.

Power shears are a great option for fabricators looking to make straight cuts in very thin sheet metal.

"For any long, straight, and fine lines, shears are the way to go," said Terry Tuerk, senior product manager, Metabo USA, West Chester, Pa. "Some shears have the capability to make some radius-type cuts. However, this option is best suited for very thin sheet metal, like a 22 or 25 ga."

There are two categories of shears available: single-cut and double-cut shears. Single-cut shears are also known as universal shears. The double-cut shear is often referred to as a slitting shear.

"The universal shear has a fixed blade and plunger blade," said Richard Carbis, national training and product manager, Fein Canada, Mississauga, Ont. "They are great for cutting a straight line. The top edge of the material will stay flat and the bottom edge of the material that is cut away will roll. It doesn’t remove any material. Instead, the material rolls under the shear as it travels through the material."

A slitting shear, on the other hand, looks like a pair of scissors. It has a middle blade that moves up and down and two fixed outer blades. This creates a strip of material that is removed.

Slitting shears cut a maximum thickness of 16-ga. material. While they are not great for curved cuts, they offer a clean cut with limited material waste. Fein

"Slitting shears are recommended for thinner material and have a maximum thickness of 16-ga. material," said Carbis. "And while they are not great for curved cuts, they offer a clean cut with limited material waste."

Regardless of the style of shear, if the tool is not properly adjusted, it can jam and potentially deform the edge. On the slitting shear, adjustment is particularly important. If the gap isn’t set correctly, this can damage the fixed and cutting blades. If the gap is too wide, this can distort the material significantly, as it will roll the edge. If the gap is too tight, the tool will jam. This can make an unwanted serrated edge on the material cut.

"Nibblers are an extremely versatile tool," said Carbis. "They can be used to make tight turns and can even do a full 90-degree turn if needed. They tend to fit into tight corners because the head of a nibbler is quite small compared to a shear."

A nibbler acts similar to how it sounds—it chews away at material in its path. This makes it less suited for cutting fine lines than the shear.

"The nibbler will cut out a wider path, approximately 0.25 in., but it will not deform either side of the material," said Tuerk. "The fact that it removes material as it cuts can be advantageous when cutting small channels or cut-outs. However, it is important to note that while the material is undistorted, it may require clean up to remove any trace of cutting and sharp edges."

A nibbler tends to create a rough edge because the cutting mechanism is actually blanking or punching out little metal clippings. Fabricators looking for a one-and-done operation should be aware that a nibbler can require that secondary edge-cleaning operation.

"And while there are not different types of nibblers like shears, the nibbler comes in different sizes as well as different shapes of the plunger and die," said Carbis. "The punch and die of a nibbler are the only wear parts on the tool and can be replaced once they begin to wear."

For more aggressive cuts, tight radii, and intricate shapes, the nibbler is a great option.

While shears and nibblers are common options for cutouts, an angle grinder can be used for making straight cuts in sheet metal. In the hands of an experienced fabricator, it may be able to cut some curves and shapes, but that too will depend on the material thickness.

"An angle grinder is probably the most versatile tool in a fab shop," said Tuerk. "They are great for cutting straight edges of cut-outs. However, on very thin material, the angle grinder can be too aggressive. It’s also important to remember that an angle grinder throws sparks and makes a lot of dust, so that can be a limiting factor."

For more aggressive cuts, tight radii, and intricate shapes, a nibbler is a great option. Metabo

In the absence of a shear or nibbler, an angle grinder is an option that is commonly found on the shop floor.

Working with power tools requires additional safety checks. For instance, corded power tools present some extra concerns.

"For those working with electric corded power tools, always make sure that it is running off an extension cord that is sized properly for the run of the cord, the length of the cord, and also the amp or the power rating of tool itself," said Tuerk. "If you have a higher-amp-rated power tool and it’s working off a long extension cord, make sure that that extension cord is a higher gauge than the tool."

Another concern with corded tools is the integrity of the cord itself. It’s not uncommon to have cut power cords when working with power tools and sharp edges.

"Some operators don’t realize just how sharp the edges can get," said Carbis. "Power cords are often dragged across the edge of the material, which can not only damage the cord but also create dangerous electrical situations. Examining the environment and taking extra care to ensure that all cords, and body parts for that matter, are kept clear of sharp edges is important."

Carbis also recommends operators take a quick look at the tool head after cutting to make sure no debris is stuck in and around the head. Debris can jam the plunger of the nibbler, causing problems. The material being cut also should be free of debris and dirt. There also shouldn’t be any weld seams in the cut, as they will affect the way the power tool cuts through the material.

A power tool is only as good as the operator, but having the best tool for the job is a good place to start.

"Beyond being aware of sharp edges, personal protective equipment is a must," said Tuerk. "Hand protection like proper gloves can prevent cuts and scrapes across sharp edges. Also, with power tools, eye and hearing protection are recommended. It’s also not uncommon for someone using a nibbler, which creates these very sharp little clippings, to find them in their shoes and pants at the end of the day. Some nibblers have collection bags as an attachment to allow for a cleaner workshop, but for those that don’t, it’s important to be aware of where all the little clippings are flying."

Associate Editor Lindsay Luminoso can be reached at [email protected].

Fein, fein.com

Metabo, www.metabo.com

Nibblers are versatile tools that can fit into tight corners because the head of a nibbler is quite small compared to a shear. Fein