hello Danielle

a 1/2 roundover is 1/2 radius. it will give you a full roundover on the plexi. you could also use a 3/8 or 1/4. each would have a smaller or less deep roundover. i think you would need to do this at slow speed. plexi is nasty stuff to work with in my humble opinion. i have not attempted to round it over, so these are just my thoughts. there are more knowledgeable people that can answer you. also the melting plexi is quite hot and burns your skin.

 

Hi Danielle, welcome to the forums
Remember that the bits are specified in RADIUS. This says that a 1/2" circle has a 1/4" radius. If you use a 1/2" radius roundover on 1/2" stock the profile would be a sharp edge at the bottom rounding up to the top surface. A 1/4" inch radius bit would yield a straight edge for the first 1/4 inch and a rounded edge leading into the top surface. If you ran the 1/4 inch along the top surface, flipped the work over and ran it again, you would end up with a rounded edge. I hope I'm not to confusing with top/bottom. It inverts on me using a table vs hand held.
If I just want to ease the edge of a piece of stock I will generally use a 1/8 inch roundover, and go to higher and higher numerical radii bits the more pronounced I want the arc.
I better quit before I confuse myself..

 

Try 1/8" first. If you don't like it, use 1/4". and so on.
For 1/2" material 1/8 to 1/4 would be best.

 

I have a door that requires an 1 1/2" round over on the side to allow the door clearance for a swing hinge (galley door style)

what size bit will I need to get round over?

 

1½'' RO....
Freud Tools | 1-1/2" Radius Rounding Over Bit (Quadra-Cut)
Freud Tools | 1-1/2" Radius Rounding Over Bit (Quadra-Cut)

 

Denise a 1.5" round over is a very large bit that should be run in a table only with a large router driving it. It is not normal to need a round over on a door edge to get it to open. What is required at times is a taper. The geometry of the taper is actually quite simple. When the door is fit in a frame you will have a given distance from the hinges across the face to the far edge. In order for the door to open without binding the distance across the diagonal from the hinges to the far inside edge has to be the same distance. On most doors I think it's something on the order of a 5 degree taper but guys who have hung more doors than I have may correct me.

 

If you are trying to round the edge of the door evenly so it swings both ways you need a 3/4 inch round over bit and do both edges


In woodworking there is always more then one way to accomplish something.

 

What Terry said...that gives you a hemisphere in cross-section.