So I picked up a Baldor grinder for cheap

[Gary Herrmann]

It's a 7306 - a .5 hp grinder designed for 7" stones.

I have an extra pair of 8" stones. I'm wondering if it will significantly shorten the life of the bearings, motor etc if I swing 8" stones on it.

It didn't come with guards, so I figured I might use the stones I have.

I was also surprised that the unit is made of steel and cast aluminum rather than cast iron. I guess almost everything gets made more cheaply eventually.

[John McClanahan]

Just make sure not to exceed the speed marked on the stones, and be sure they are well balanced. With no guards, it sounds like it is a buffer.

John

[Gary Herrmann]

No, it's a grinder. The guards were just lost at some point. I have another 7306 with the guards.

[Greg Portland]

I'm confused, the "guards" to me are the cast iron pieces surrounding the wheels (7309D is cast, 7309 is pressed steel). You can't fit an 8" stone into the cast 7" wheel guard. Also, the work supports are mounted to the guards and you'll need those unless you're mounting some aftermarket jigs (lathe tool sharpening, etc.).

Personally I will not operate these tools w/o functional guards because the wheels have been known to shatter.

[Frank Drew]

Agreed; don't use a grinder with unguarded wheels, and don't grind on the side of the wheel.