A quiet revolution has been taking place. A revolution in the way you can cut metal in the shop or on the job site that is. Actually, it’s not all that quiet during the cutting. Pretty loud actually, but it is faster, cleaner-cutting, and more efficient. You know what I mean. After attending Diablo Tools’ latest media event at STAFDA recently, I learned a lot more about their goal of replacing abrasive metal cutting with better methods to make metal cutting easier for the contractor or DIYer alike.
The big difference is using carbide teeth to slice through metals, teeth like those that revolutionized wood cutting blades a few decades back (mid-1980s-ish). Before carbide tooth wood blades for construction and woodworking were commonly available, there were hardened steel blades that had to be sharpened and set when they dulled. That, or thrown away. Today, quality carbide woodworking blades are worth having resharpened, while construction grade blades are usually tossed out when worn. But the big difference is that modern carbide blades withstand significantly more cutting mileage than the old all-steel blades. We take it for granted now that you can build a house or two with one inexpensive blade in your circ saw, even when clipping through nails once in a while.
Which gets us back to the point. Compared to steel or iron, wood is fairly easy to cut. Hard carbide teeth were traditionally too brittle to slice through ferrous metals, so the teeth on early carbide construction blades would shatter or break off if you ran into a nail. I remember neatly ripping a 16-penny nail down its length during some demolition work with my first carbide tooth circ saw blade. I also remember driving to the store right after that to spend 20 bucks on a new blade. I remember so well because I kept that bisected nail as a trophy of my straight-line ripping accuracy at least, not my aim. Hey, anyone want to buy a cool half-nail for 10 bucks? I have two of them!
Fast forward to now-times and newer formulations of carbide have tempered their unforgiving hardness with varying degrees of shock resistance to be able to handle harder and more abrasive materials than just wood. So not all carbide teeth are the same; there are specialty teeth for fiber cement siding, laminate flooring, plastic composite deck boards and PVC trim, and metals of all types. These customized formulations are the foundation of the metal cutting revolution, and Diablo makes its own carbide, which they say is the key to being competitive in this market.
So consider the most common ways to cut metals, ranging from the spring steel of band saw blades, to hard yet flexible bimetal recip saw blades, to bonded abrasive wheels for circ saws and chop saws, and even to longer-lasting abrasive wheels with diamond grit. Diablo is seeking to provide replacement carbide tooth cutting solutions for all of those applications. According to the company, carbide raises the cost compared to other types of blades, but it can offer up to 50 times the cutting life for that extra investment. Diablo wants to be at the forefront when various parts of the industry hit the tipping point in favor of carbide tooth cutting over the old standby methods. After all, when steel teeth were overwhelmingly replaced with carbide for cutting wood, no one ever looked back. Ever.
Reciprocating Saw Blades
Cutting metal with a reciprocating saw is a fairly common use, especially in remodeling work. Think about it. When you demo studs or blocking, you are usually cutting through the nails at the wood joint, and not much of the wood itself. That’s why demolition blades are designated “for wood with nails”. So whether removing framing or salvaging any lumber for reuse, it’s usually easiest to cut boards apart at the fasteners. And one pro tip for this kind of work is to use a finer tooth metal cutting blade to sever nails instead of a coarser demolition blade. Taking smaller bites to chew through a nail is much easier on you and your saw than trying to tear through it with large teeth. The thing to avoid is getting a nail hooked all the way inside of a tooth’s gullet. Beside the jolts to your joints, it’s an easy way to break off a tooth entirely. In my comprehensive blade testing, I have found that the skinny #8s in my test boards were responsible for breaking and distorting saw teeth, and not the much larger 16-penny nails.
Diablo has six different carbide tooth configurations for their recip saw blades. The coarsest carbide teeth I’ve ever seen on a recip blade belong to the pruning/clean wood blade with 3 giant teeth-per-inch (TPI). A bit of a departure from our metal-cutting focus, but it’s notable that these blades fitted to a recip saw are replacing chain saws in the Christmas tree corral for at least one major home center. Removing the need for novice employees to don safety chaps and figure out how to run a chainsaw sounds like a smart idea to me.
Diablo’s nail-embedded and general purpose blades both feature a variable progressive tooth pitch which changes the spacing of the carbide teeth gradually along the blade’s length. With the finer pitch at the saw’s shoe and the coarser pitch toward the tip of the blade, this configuration helps index thinner material back toward the finer teeth. The nail-embedded wood blade graduates from 5 to 7 TPI, and the general purpose from 6 to 9 TPI. The 6/9 general purpose seems numerically close to 5/7 nail-embedded blade, but the general purpose has a flatter tooth grind to work better on metal and plastics.
The remaining three blades are all designated for metal cutting only. The 8 TPI “thick metal” blades are optimized for metal from 1/8 up to 1/2 inch and the 10 TPI “medium metal” from 1/16 up to 1/8 inch. All of the blades previously mentioned have teeth individually brazed or welded onto the steel blade body. To make carbide teeth any smaller, Diablo attaches a thin strip of solid carbide to the blade body and grinds the tooth profiles into it. This is how the 20 TPI “thin metal” blade for metals less than 3/16 inch thick is fabricated.
Flush cutting by bending the blade into a curve should be okay for carbide tooth blades with individual teeth, but is not recommended for blades with carbide teeth that are milled out of a strip of carbide, which can crack if bent.
Trendy Tips for Palletwrights
For all of you pallet-wood crafters out there, forget prying and pounding away at your flat little lumberyards. Surgically removing the nails with a slim metal-cutting recip blade tucked between the boards is the real way to get ‘er done. You can dissect a pallet this way in a few minutes without smashing and splitting the wood. For the nails not accessible from the outside edges, the flexibility of a recip blade allows you to curve the blade to get to the thin top boards from underneath when needed (known as flush cutting). But as mentioned above, if you are using a carbide tooth blade, make sure it has individual teeth. Teeth milled in a solid carbide strip will crack when bent sideways. For this rough work though, it might be better to beat up a more affordable blade. The best blade would probably be the Diablo DSO914BF bimetal blade with its 14/18 tooth pitch and minimal kerf thickness. A nail-embedded wood demolition blade would also work for this application, but its bigger teeth and wider tooth set is optimized for clearing wood waste and will leave more distinct tooth marks on the wood on either side of where the blade passed through.
After slicing through the fasteners, the nail heads are easy to pop out of the thin decking boards with a thin nail set or punch, but keep in mind this method leaves nails in the stringers. If you are ripping or crosscutting through them later, you may want a blade like this next one.
Circular Saw Diablo Blades
For cutting through both wood and metals with your circ saw, Diablo has new combination blades to fit 6 1/2- and 7 1/4-inch saws (priced at $25 and $22 respectively). Not only is this blade designed for nail embedded wood applications like demo work or processing reclaimed wood, but it’s also made to be used on wood or metals separately. In wood materials, the 36 teeth of the 7 1/4-inch size blade make it somewhat of a fine-tooth framing blade. In metals, the blade is specified to handle steel studs, angle iron, channel, and flat bar stock from 3/32 to 1/4 inch thick, as well as threaded rod up to 1 inch in diameter.
For more specialized metal cutting with a circ saw, Diablo added a new blade to their Steel Demon line with Cermet teeth, said to be the only 7 1/4-inch blade available with Cermet. What is Cermet? According to the brand, “Cermet (Ceramic and Metallic) teeth provide a high heat tolerance and increased hardness for superior wear and impact resistance; lasting up to 5X longer than standard carbide metal cutting saw blades”. One benefit of these specialty teeth is that the same blade can be used for both mild steel and stainless steel—materials that typically require separate blades. The new 7 1/4-inch blade ($30) has 48 teeth, and is designed to cut conduit, steel studs, and structural metals from 1/16 to 1/4 inch thick. Diablo already makes circular Cermet tooth blades in 8-, 9-, 10-, 12-, and 14-inch diameters, but they’ve added blades for smaller handheld saws in 5 3/8-, 6 1/2-, 6 3/4-, and 7 1/4-inch diameters.
Chop Saw Blades
The larger diameter Cermet blades mentioned above are for use in stationary metal cutting chop saws (aka, cut-off saws), but not all chop saws are the same and the blades aren’t compatible between the two types. Old-school saws that use bonded abrasive wheels run at a higher rpm to maximize cutting friction. If you’ve ever cut thick steel with one, you know that you are essentially melting though the steel with the abrasive and you don’t want to let off the pressure until the cut is through. Once you initiate the cut and the abrasive gets hot enough in the cut, it progresses steadily, but if you back off during the cut, the metal cools which causes a delay every time you push down again.
The huge shower of sparks made when cutting with abrasives is little molten scraps of the steel exiting the kerf. The melting action of the cutting is what makes the end of the cut distorted and too hot to handle. One other disadvantage of using bonded abrasives is that as the wheel wears, your available cutting depth is significantly reduced. Diamond grit abrasive wheels are a step better as they don’t wear down dramatically and are able to cut a variety of materials. But they are still cutting with abrasives in a grinding action instead of cutting with sharp teeth.
Metal chop saws that use blades instead of abrasives (aka dry-cut, dry-cutting saws) run at a slower rpm as they don’t need to heat up the metal to remove it from the kerf. Cutting with big diameter blades like Diablo’s Cermet tooth models leaves a cleaner cut end that doesn’t require a lot of cleanup effort. It’s simply a more efficient way to cut metal.
It’s too bad in a way. It may be counter-revolutionary, but we tool journalists love the abrasive saws. The flaming, flying spark photo ops at media events are among our favorites to take and post because they look so cool. But the metalworker in me welcomes the change. It means that someday I won’t have to drag my chop saw out of the workshop and into the yard for fear that one errant spark might ignite something flammable under the workbench. I really prefer to prevent some local newspaper journalist from getting their own cool, flaming photo op. Viva la Revolution!
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