Another way to go with an old lawnmower blade! We have tons of these around the farmhouse and a blade like this is always handy.
Make yourself a nice sheath and you have something for ATV!
Knives and All Things in the Making of Knives
Making a knife or machete from old parts This a great idea and lots of fun to create. Found this on Instructables, and it worked like a charm in the thick brush and forest areas. You can modify it to suit your own needs very easily.
Learn more here: http://www.instructables.com/id/Lawn-Mower-Blade-Knife-and-Wooden-Handle-and-Sheat/
Great way to get started making your own knives. Easy to make, adjust and modify. I started with this one, still use it. Great tool for those starting out!