He didn't have a brush cutter, but he has a Plasma cutter...

My nephew did this with Amazon's Cheapest Plasma Cutter.

I can't decide if it's a horrible idea, or a brilliant idea.

He still needs to change the blade and put the wheels back on.

I am leaning towards the terrible side, Brush cutter blades are hinged so when they hit something they give, this could very likely bend the crank when it hit anything of substance. But you are there now, give it a whack and tell us how it goes.

Poor blade.  should have been put to rest a long time ago.

That's a really bad idea that is going to get someone hurt.  

As pointed out a brushwacker blade pivots but not just to protect the engine.  When the blade contacts something firm the hinge keeps it from fatiguing and breaking and flying in the direction of rotation.  It allows for strain relief on the back of the blade.  Imagine hitting a tree with the middle of a golf club shaft at full swing.  The shaft is going to break and the head will continue on straight ahead liberated from the centripetal pull of the shaft.   The hinge allows this energy to be momentarily disipated and then the blade can fold If necessary if it hasn't aihilated what is in its path.

No imagine that that club head is the last 3" of a lawnmower blade spinning at 3600 RPM.  How far do you think that would embed itself In someone's shin..

Thanksgiving might be a bit awkward this year in the Woody household. 

I had a D&R Field and Brush mower. Thing took out 3" diameter trees with a setup sorta like that. No hinge on the blade.

I think it's a bad idea, but if he really wants to use it I'd consider running a 14" circular saw blade backwards so that it doesnt grab and kick. He won't have much cut depth and that's probably for the best. 

To get an idea how different blade types are likely to react when they hit different things, i'd review the top 3 videos here: https://www.youtube.com/results?search_query=project+farm+brush

I clicked on this thread worried that he'd attempted to landscape with the plasma cutter directly.

Old blade + New blade + Grade 8 hardware = Winning. 

I heard of someone doing this, with a hotrodded engine, and a lot of weight added to the blade.  It was cutting through trees.

Found it!

https://yarchive.net/car/hotrod_lawnmowers.html

You outta seen the Gravely tractor from Hell we built to clear our
first yard.  We bought a HUD repo house whose yard had reverted to woods.
A friend had an old Gravely that did not run which was donated to the effort.
After welding the wheels on to replace the rusted off nuts, the hotrodding
began.  A little port work, homemade manifold, 32 mm Mikuni carb,
header and megaphone and a bit more compression on the old side valve
flathead.  And after the first attempt at starting it, a hopped up
starter motor :-)  Fuel was 20% nitro in methanol.  IN the blade
arena, the front third of the blade housing fell to the acetylene torch.
About 5 lbs of steel was welded to the blade for a bit more inertia.

This lot contained mostly bramble with blackberry thorns and
trees up to about three inches in diameter.  Procedure was to
don a set of duck  canvass ironworker's coveralls and then a
second pair, some GI boots, goggles, a gas mask and ear plugs.
Crank that sucker, set the throttle to bellow, trip the drive
clutch and let the thing wade into the mess.  Dodging the
falling trees was the worst part.  Dodging the thing when it
bounced up in the air was a close second.  When it broke through
the other  side and just before it ate the neighboor's dog, rush
up and pull the  clutch.  I cleared that lot in about 8 hours.
My wife still carries a picture in her wallet of my operating that
thing :-)

Any port in a storm...

Toyman01 (Moderately Supportive Dude) said:

Old blade + New blade + Grade 8 hardware = Winning. 

Loose bolt = losing.  Your feet.

MadScientistMatt said:

I clicked on this thread worried that he'd attempted to landscape with the plasma cutter directly.

Especially when posted by a fire fighter. I'm actually a little disappointed.

In reply to A 401 CJ :

You sure can't use cheap or small bolts. Probably pay to inspect it on a fairly regular basis for wear as well. 

A little bit of 1/4 plate across the back of the deck might be a good idea as well. 

I don't think anyone has mentioned it but with that much of the deck missing you will be launching projectiles like gravel, stones, chucks of wood and anything else at very high speeds out the front.