15 posts / 0 new
Last post
qhwang
Crown molding coping question

I learned how to cope a inside corner by a simple hand coping saw on Internet --- have a 45 degree angle cut, then cope. I did some practice yesterday, the result was frustrating. I don't know where I did wrong. Is 45 degree angle cut just for the molding with 45 degree spring angle, or for both 45 and 38 degree spring angles.
My molding is 38 degree spring angle. Should I have 38 degree angle cut then coping?

A. Spruce
Re: Crown molding coping question

A 90* corner, divided by 2 is 45*, regardless of the spring angle of the crown. You will cut the molding at 45*. Where you are probably running into trouble is proper placement of the molding in the saw when you're making the initial cut. If it is not oriented properly, then it's not going to mate up properly when installed.

I recommend adjusting the placement of your trim in the saw until you're getting the correct cut, then either draw a scribe line or install stop blocks on the saw to line up the trim perfectly every time.

Once you've got the cut right, then you cope the end with a 5* back bevel, this will give you tight face joints that stay tight.

qhwang
Re: Crown molding coping question

For a right inside corner coping, I remember I lay the trim flatly under miter saw, with up side touching the fence, then had a 45* cut. Now you convinced 45* initial cut is correct, I'll have more practice. Thanks.

JLMCDANIEL
Re: Crown molding coping question
qhwang wrote:

For a right inside corner coping, I remember I lay the trim flatly under miter saw, with up side touching the fence, then had a 45* cut. Now you convinced 45* initial cut is correct, I'll have more practice. Thanks.

No, you place the molding in the saw upside down, with the bottom against the fence and the top out from the fence at the spring angle. Watch this video http://www.youtube.com/watch?v=pvRpmpfeCr0&feature=related

If you want to cut the crown flat you need to set up a precise angle and bevel angle. For 38 degree spring, If I remember correctly, you need a 31.6 degree andgle and a 33.9 degree bevel. I personally prefer the first method.

Jack

Jack

qhwang
Re: Crown molding coping question
JLMCDANIEL wrote:

No, you place the molding in the saw upside down, with the bottom against the fence and the top out from the fence at the spring angle. Watch this video http://www.youtube.com/watch?v=pvRpmpfeCr0&feature=related

If you want to cut the crown flat you need to set up a precise angle and bevel angle. For 38 degree spring, If I remember correctly, you need a 31.6 degree andgle and a 33.9 degree bevel. I personally prefer the first method.

Jack

Jack

See this video at around 2:18. http://www.thisoldhouse.com/toh/video/0,,20056482,00.html
And this article http://www.homedepot.com/webapp/catalog/servlet/ContentView?pn=Cutting_a_Cope_Joint_on_Crown_Molding

They don't say should put trim upside down. Maybe they miss details. I'll try as you suggested.

A. Spruce
Re: Crown molding coping question
qhwang wrote:

For a right inside corner coping, I remember I lay the trim flatly under miter saw, with up side touching the fence, then had a 45* cut. Now you convinced 45* initial cut is correct, I'll have more practice. Thanks.

Laying the molding flat on the saw is not accounting for the spring angle, which is why you're not getting the pieces to mate properly.

A. Spruce
Re: Crown molding coping question
qhwang wrote:

See this video at around 2:18. http://www.thisoldhouse.com/toh/video/0,,20056482,00.html
And this article http://www.homedepot.com/webapp/catalog/servlet/ContentView?pn=Cutting_a_Cope_Joint_on_Crown_Molding

They don't say should put trim upside down. Maybe they miss details. I'll try as you suggested.

It is easy to forget an "obvious" step when you know what you're doing, so as a novice DIY'r, you can't take a single how-to process or video as gospel. It will take trial and error on your part to ferret out the process that works for you.

What I would recommend is that you forget about those videos for a second and just miter cut yourself some template pieces of trim so that you understand how to orient the material in the saw to get the cuts you need.

Set the saw at 45*. How you place the material into the saw will depend on whether you're cutting an inside or an outside corner. Cut yourself a set of inside corner and outside corner template pieces. Now, you can simply place your template piece into the saw to set it up before you start whacking away at your lengths of molding.

If memory serves, holding the material upside down at the correct spring angle against the saw fence will produce an inside corner. Holding the material right side up and facing the fence at the correct spring angle will produce an outside corner. Once you have your template pieces you'll never question saw orientation again.

JLMCDANIEL
Re: Crown molding coping question

ghwang, you might consider a $30 investment in http://www.kregtool.com/CrownPro-Prodview.html

Jack

Mastercarpentry
Re: Crown molding coping question

More suggestions:

Until you learn to cope accurately with a saw, don't cut to the edge- stay just a tiny bit shy of it, then use sandpaper, rasp, or file to get that last little bit. It's easier to control wood removed with these than with a coping saw. To find the edge you're cutting to easier, run a pencil held flat across it to make it more easily seen. When undercutting, think about how the corresponding part will fit so you can angle your saw correctly as you undercut too.

Once you understand the basics, one piece crown molding is really pretty easy till you get to corners that aren't ostensibly 90 degrees or when you're running 2+ piece crown- that stuff can drive a perfectionist to drink in a decent home and drive you nuts in a bad one!

Phil

qhwang
Re: Crown molding coping question
JLMCDANIEL wrote:

ghwang, you might consider a $30 investment in http://www.kregtool.com/CrownPro-Prodview.html

Jack

That saw looks very helpful and price is also very good. The saw I'm using is a compound milter saw borrowed from my friend. I have a good friend. We invest different tools then share. We also share diy knowledges. My inside corner is not tight enough, so I want to try coping.

qhwang
Re: Crown molding coping question
A. Spruce wrote:

It is easy to forget an "obvious" step when you know what you're doing, so as a novice DIY'r, you can't take a single how-to process or video as gospel. It will take trial and error on your part to ferret out the process that works for you.

What I would recommend is that you forget about those videos for a second and just miter cut yourself some template pieces of trim so that you understand how to orient the material in the saw to get the cuts you need.

Set the saw at 45*. How you place the material into the saw will depend on whether you're cutting an inside or an outside corner. Cut yourself a set of inside corner and outside corner template pieces. Now, you can simply place your template piece into the saw to set it up before you start whacking away at your lengths of molding.

If memory serves, holding the material upside down at the correct spring angle against the saw fence will produce an inside corner. Holding the material right side up and facing the fence at the correct spring angle will produce an outside corner. Once you have your template pieces you'll never question saw orientation again.

Practised again last night, following what I learned from you guys, putting upside down and 45* milter cut, it was much better. I did much research about crown molding installation in advance, but didn't decide coping. Two years ago when I prepared to install a hardwood floor, A. Spruce answered my questions and gave good advices. My job was decent for a amateur. Hopefully this time is the same.

Pages

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.