[Verboten]

Hello,

If you need it to be exactly perpendicular to the ground and the other parts of your machine then you might want to consider making it adjustable.

This might sound like a lot of work but it goes fast:

You could buy a larger piece of thicker plate to bolt to the ground (say 1/2 or 3/4 x 8 x 8) , center your smaller plate and tack the two together pretty good. Then you could drill 4 holes through both near the corners of the smaller plate (say 5/16 ths to tap the bottom with 3/8 nc). Then mark the pieces with a punch or something so that you know how to assemble the parts then seperate them. Now you can thread the bottom plate and drill it with 4 more holes near it's corners to bolt it to the floor. Then enlarge the holes on the smaller piece.

Then you could decide if you wanted to use shims to adjust or you could drill and tap the smaller plate twice more per side for setscews to use for adjustment (probably wait until after welding to tap). Then weld on the pipe as straight as you possibly can (most likely it won't be "perfect") and assemble.

I like ESjavik's suggestions - magnets and clamps can only hold steel straight until you start welding after that its technique.

Good luck with your project.