Advice on "welding" two pieces of plastic together...

Sorry I took so long to get back to you.

You have several options

If your window pillar is thick enough (and you line it up PERFECTLY ) you should be able to drill a hole into each end of the break. I belive a #80 drill bit should work. Once you have the hole drilled insert a small bit of wire into one side then press fit the two pieces GENTLY into their position. Use a liquid cement to "weld " the to pieces together.

A kind of iffy fix would be to cut a small piece of clear sheet styrene( the thinner the better ) and glue it to one side first leaving a little overhang Once that dries you can glue the other end of the piller to itself without having to hold it right at the glue joint. (Work from the inside not the outside.)

There will probably be some sanding and if your like me ... some glue to remove from your fingers.

You can also line up the parts and cut a groove accross the break. Then insert a piece of plastic in the groove like a splint and glue one end at a time.

If all else fails you can cut the entire pillar off the car and line it up on the workbench. then glue it back onto the car.

This last bit of advice is sugested as a "last resort" 

I find that screaming helps.......  sometimes. 

I'd second the recommendation of using wire or a pin---if possible---to give the repair some extra strength. But rather than gluing and puttying, I'd suggest trying one of the "5-second fix" -type products, one of my new favorite tools for such problem areas. When cured (instantly) the resin is virtually the exact hardness of styrene, very easy to shape and sand smooth without any 'feathered' edge showing. (Also seems to take paint well.) Give it a try.

Good luck.

Thank you for all the replies.

The thick (gel) CA will fill some gap- as much as a sixteenth of an inch or so, and still give pretty strong joints.