Often wondered about using a blade on a weed eater. Seems like there would be a lot of kickback.
Depends on the weed eater and the blade mass. If the power head has enough weight to horsepower ratio, it isn't too bad, IF the blade is used correctly. It's more a sidekick/twist, but it will usually stall the speed pretty quickly with most blades. It takes a little longer to accelerate the mass of the blade than a string trimmer (for obvious reasons), meaning it also takes a bit more to stop it. It WILL toss a lot more larger grit/gravel debris back at the operator because they typically don't have a guard like the string trimmers do, but they're intended to use for cutting brush above the soil line. They don't have much draft, meaning they don't pick up loose material so much, but they have a very high tip speed which means they'll typically shatter small rocks and turn them into shrapnel. Blades are pretty rough on the bearings and gears in the cutter head. Lots of severe impact. They also dull very quickly. Pretty amazing how tough those little buggers are, though. I typically start seeing grease leaks in the gear boxes after using a blade for a while. Blades are what I started clearing my property with. Just watch out for seasoned pine knots and rocks. The shards/chips hurt when they hit, even through thick jeans. I've picked more than one sharp splinter out. I've also seen some folks use table-saw blades on them. I can't think of anything that would be much more dangerous. Blades normally require some sort of adapter as well as some work to remove the string head. I bought a second head for mine at one time just so I could leave the blade on. I don' t use the blade anymore because I found something better, and a lot less dangerous.
As an experiment last year, I decided to try out my hedge trimmer attachment in the thick grass and brush on the ditch banks that run across my property. I was more than impressed at the performance. That thing made cleaning ditch banks a breeze, and it's a LOT faster than a string trimmer at laying down heavy grass on flat ground. Unlike a string trimmer, it doesn't wrap around small brush and beat the line off, it just cuts down the small brush. Since it uses overlapping shear blades, it'll clip anything up to about 1/2" diameter like hot butter; green, dry, doesn't matter. Lower engine speed makes a tank of fuel last a longer too. Being able to vary the angle of the hedger head also eliminates some of the wrestling with the power head weight, i.e. makes it a little more ergonomically friendly. Most blade attachments are no more than about 8 inches diameter. A hedger bar is 20+ inches, and doesn't throw stuff at ya. Hard to beat it for laying down brush in places you can't get with a mower. I haven't used a blade since. I stand on top of the ditch banks and just reach over the side because the hedger gives me a lot more reach. I also have a couple 3' extensions which are meant for the pole saw, but they work well for the hedge trimmer, too. Just like a blade though, ya gotta keep it outta the dirt/rocks if you want to keep it sharp. I use a round file to doctor mine up if I find a piece of steel wire or something harder than the teeth. The hedger head is pretty heavy, but a slight adjustment of the handle on the shaft remedies the balance issue pretty quick.
Look into some of the Trimmer Plus attachments from Troy-Bilt if you have a power head that will accept different attachments. I'm thinking there is a separate blade attachment in the Troy-Bilt line of attachments that I know will fit on a Stihl power head. My son has one of the 4-cycle Stihl heads, and all my attachments work just fine on it.
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