you say end...
is it really the edge and do you want a round over the the full thickness of the 2by???
how large is the piece??

at a guess from what you show/say you want a 1½'' radius router bit...
do you have a router??

 

yes the full thickness of the 2x4 and the image is a side view, and I've got 2 routers but can explain what a 1½'' radius router bit is and how it can help me? thanks.

 

I think I am starting to understand what you are saying. you mean I should route it from the top and let the router make the curve? that is brilliant! is that what you mean?

 

yup...
the bit looks like this....

..

 

How long is the 2x4? And you want to round over the entire length, right?

 

no the width. the 2x4 is about 3 feet long but I need just that end to be rounded. i will add dimensions to the image. this is an image of the side of the 2x4.

 

now we need more information as in details in order to help you proceed safely...

how long are the pieces???

 

I would likely cut it a tad oversize, then sand it to final shape.

 

so according to what I am understanding I will need a 3½ inch radius bit, correct? does that even exist?

 

correct..
the bit, actually a cutter, does exist but that will take a shaper to turn it... not a router..
what you are showing is the face of the 2by and the ends...
the edge is 1½'' thick...

rough cut it to size and sand to final...
an ROS will do it...
as well as a disk, belt or drum sander...
a disk sander will do the best job..
2nd choice is the belt sander...
make the tool stationary and move/rotate the wood over the sanding surface...
all w/ a little practice you'll get what you are looking for...

 

This is a job for a bandsaw (or a jig saw) and a disk or belt sander. You will NOT get a round-over bit with a radius of 3-1/2": that's a bit with a diameter of over 7". Instead of sanding you could pattern rout it. You would need a 1/2" collet router and a flush-trim bit with a cutting edge of 2". If the 4x2 is in fact only 3-1/2 x 1-1/2 you could do it in two passes: the first with the pattern and a pattern (shank-mounted bearing) bit with a 1" cutting edge and a second pass (from the opposite face) with a flush-trim bit.

Denis Lock - "Routing with Denis"

 

I think this is the end result he is after.

 

no...
he wants a 3½'' radius..
so that's edge to edge, not face to back as you show...
rotate it 90°...

http://www.routerforums.com/1673897-post8.html

 

Maybe put two boards together and use a circle cutting jig for the jigsaw. Then sand 'em. ???

 

Use a template and a pattern bit. rough cut it 1/8" larger then finish with a router either hand held or a router table.

Industrial router bits-Pattern router bits, long series-CMT tools

http://www.cmtutensili.com/show_items.asp?pars=RB~7/8/906~2~2~3

Herb