Cutting Fiber Cement Siding

By Michael Davis

This stuff is tough to work with, but toolmakers are finding ways to ease the pain and control the dust.

Fiber cement siding is unlike any other siding product I've ever worked with. When I won a job to hang it on several three- and four-story buildings, I knew I'd learn a ton about working with it. I set up my scaffolds, tooled up the crews, and we were off to the races. It quickly became clear that cutting fiber cement siding is the trickiest part of working with it, so we tested four ways to attack it. We used stationary shears, handheld shears, special circular saws and blades, and simply scored and snapped it.

Stationary shears. For the contractor who measures siding jobs by the square mile, not the square foot, I think the $1,150 Pacific International SS110A Pneumatic Production Shear is the Cadillac. It's got smooth roller tables and a backstop for feeding material in and out of the tool. And since you operate the blade with a foot pedal, you have both hands free to work. It's super-fast, efficient, and dust-free'a major plus. Unfortunately, the SS110A isn't very portable. The three parts (main platform with shear and two roller tables) weigh 175 pounds and take about 10 minutes to set up. And this tool only makes 90-degree cuts, so you'll need other tools for angles and notches.

Another fine'and lower cost'tool from Pacific International is the $650 SS210M Manual Production Shear. Its 24-inch-wide blade lets you turn a piece of siding in the shear and make long angle cuts for gable ends. As the name suggests, this model is hand-operated (no foot pedal) and it takes some serious muscle to make a cut, especially a long miter cut. Since the 54-pound tool is portable and doesn't require electric or air power, it's a one-second set-up. Again, you'll need other tools for ripping and notching.

Handheld shears. This is probably the most popular method for cutting fiber cement siding. Handheld shears or 'snippers' look like drill-powered tin snips and cost around $260. They come in two flavors: electric and pneumatic. I tested electric tools only. Beyond that, there are shears for cutting straight lines and wide radius work and tools for cutting scroll work and circles.

Porter-Cable's 6604 and Pacific International's Steelhead are top-quality snippers. Both make clean, fast, and dust-free cuts. And when the blades dull (after about 25,000 lineal feet of fiber cement siding), you can easily replace them for about $65. We really liked Porter Cable's built-in belt clip, especially on the scaffold. Pacific International's Steelhead is built on a dependable 7-amp Milwaukee motor; the company says it's the most powerful handheld shear on the market.

The snippers above will make wide radius cuts in fiber cement siding, but Pacific International's SS410 Whippersnapper is the tool you need for amazingly tight radius work like arches, radius gable vents, scrolls, and holes for air conditioning pipes.

Shears do have a downside: They can only cut one thickness of siding and can't cut 3/4-inch fiber cement trim boards, whereas a 7-1/4-inch circ saw can gang-cut five pieces of 5/16-inch siding in one pass. While it might seem like a no-brainer to use a saw instead of snippers, bear in mind that gang cutting is great, but the heaping piles of choking dust aren't.

Siding saws. Makita and Hitachi manufacture saws specially designed for fiber cement siding. Each tool takes a different approach to collecting and/or controlling dust.

Hitachi's 7-1/4-inch C7YA circular saw contains the dust in its extended blade guard; the blade's rotation then ejects it through a tube in the back. If you really need to settle the dust cloud, Hitachi has a dust bag (like you'd find on a miter saw or sander) that fits on the ejection tube and works well. The larger blade guard makes it difficult to see the blade where it contacts the material. The guard is adjustable but I recommend leaving it down to stop the most dust, then relying on the saw guides to make your cuts.

Makita's saws have very tough, clear plastic catch reservoirs affixed to their upper blade guards. As the blade spins up through the material, dust goes into the reservoir enclosure. When the reservoir fills up, you open a door at the back and empty it out. Like Hitachi's model, the dust-catch assembly makes it difficult to see the blade. However, the cutting guides on the saws' bases are accurate. Both the Hitachi and Makita tools work well and significantly reduce airborne dust. Makita's bearings and switch are dust-proof, which'll keep the tool running longer.

Makita offers two sizes of dust collecting circular saws: the 4-inch 5044KB and the 7-1/4-inch 5057KB. The 5044KB's small size and low weight make it a dream to use up on the scaffold. Its big brother, the 7-1/4-model, is a real workhorse which I prefer using on the ground for gang cutting.

If you have zero tolerance for dust, pair the Makita 5057KB saw with the company's XSV10 Type 4 shop vacuum, which you attach to the saw's exhaust port. This arrangement reduces your mobility, but the result is almost magical'no dust.

Score and snap. As we approached the end of 16 solid weeks of siding, an interesting anomaly developed. Every imaginable siding cutting tool was available on site, yet one of my most productive teams cut most of their siding by scribing the back of the board with a utility knife and snapping it over a 2x4. Cut this way, siding breaks cleanly as long as you scribe it uniformly.

My guys used a metal rasp to smooth any rough edges. Like the rest of the teams, they had a ground-based cut-man for repetitive measurements and special cuts around windows. Everything else they scribed and snapped on the scaffold. Their work was clean and they hung as much or more siding as any other team.

Michael Davis is president of Framing Square in Albuquerque N. M., a large framing and trim company.

Cement Siding Blades

Fiber cement siding manufacturers say you can cut the stuff with any good-quality, carbide-tipped blade. I got two hours out of a thin-kerf, 24-tooth carbide blade on my wormdrive before sparks shot out where it contacted the siding.

Despite what manufacturers say about standard carbide blade use, I think going through four blades a day is too many. You really need special blades to cut this stuff affordably and productively. These blades will reduce (but won't eliminate), dust and'unfortunately for me'they only fit on a sidewinder.

Oldham, DeWalt, Irwin, Hitachi, and Makita (to name a few) each make blades for this stuff, but long before specialty fiber cement siding blades hit the market, installers cut it with continuous-rim diamond blades like those from MK Diamond and Pearl Abrasives.

TOOLS OF THE TRADE Magazine, March/April 2002

Sources of Supply

Shears

Pacific International

Tool & Shear

800-297-7487

www.snappershear.com

Porter Cable

800-487-8665

www.porter-cable.com

Circ saws and blades

Hitachi Power Tools