cmulder

So I purchased a DeWalt 4.5 inch grinder (DWE4011) specifically to cut some concrete--I also purchased an Avanti pro 4-1/2 turbo diamond blade which the Home Depot person told me was best for this job. When I open up the box and read the instructions its says I need a Type 1 guard (add on accessory) to use this blade. Its also very confusing as to how to install the clamp nut (flat side down or up) as apparently this changes base based on the wheel. The blade came with a "ring" that fits in the one side of the clamp nut so I assume that side goes down. So do I need to that guard? Because it attaches fine with the Type 27 guard that's on there. What's the purpose of this guard? Is there another model that does not need a separate guard? I'd rather pay for a better model then but the guard.