I need help to cope a inside 45 on crown molding

Practice on a scrap piece. Trace the pattern on the back as usual. Then set a jig saw to 45 degrees and cut it, and see how it looks.

Google is your friend. Found this
this old house article

There are easy ways that involve turning the molding upside-down and treating the fence and base as if they were wall and ceiling.

The first piece of crown goes square into the corner. The second is inside mitered at 45 degrees. If you visualize the fence as the wall and the table of the miter box as the ceiling, place the crown in the miter box just like it gets installed. ("In-postion" cutting) You may have to put the piece of crown "upisde down" in the miter box so you get the proper miter for coping. Your going to cut the piece in a reverse 45. Just like if you were to miter your inside corners. You then cut the "waste" area the miter. Use a coping saw, its much eaisier than a jig saw. (unless you have a Collins coping foot) When you cope the miter, angle the coping saw almost at a 45 angle opposite the angle your coping (back cutting the miter). This makes your coping line sharp and eaiser to match against the profile of the other piece of crown. Hope this isn't too confusing. Depending on how new your miterbox is, do you have a compound miter saw? The saw goes right & left but also the blade tilts? If so, you should have set indentations on the saw for crown moulding cuts on the "flat". That's another lesson.

I have installed a lot of crown moulding in my house. It is a cheap way to add a touch of elegance.

When possible, I try and use corner blocks as I a have a hard time getting a coped joint to fit. The tips from the other guys are wonderful and I will use them the next time I do a coped joint.

And, remember, caulk is a carpenters and painters best friend.

Good Luck, Dan

Carpenters Don't Caulk, Painter Do. Lol.
The First Piece Is Cut Square To Square The Second Piece Will Be A Long Point To Square, If You Left Handed You Need Work To The Left Side Of The Room , If Your Right Do The Other Way, Reason Being This Will Alow You To Cope With Your Good Hand, I Want Explain The Actually Coping Since It Has Been Done. Good Luck Nichols Trim

Thanks for people who are trying to help by posting an answer to the question.

I hope that people posting an answer to this have noticed the date on the original post.

I would think that the original poster has probably already found an answer to their question.