Home>Discussions>INTERIORS>Molding & Carpentry>Trimming a Window with a Radius Top
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Ernest T
Trimming a Window with a Radius Top

I need to trim a window 48 inches wide that has a top with a 51 inch radius. I already had a flexible molding made to match the top radius and now I need to install it, but don't know what angle to use to match the side pieces to the top or how to even cut the top for that matter since it's curved.

Any suggestions?

jkirk
Re: Trimming a Window with a Radius Top

to find the angle you have to install the top peice first but you need to draw the radius on the wall along with the reveals on the jamb extension.. from there you can bissect your angle to get a good idea what it should be. as for cutting, its tricky on a mitre saw because the trim is so floppy.. a very very sharp japanese pull saw is what i typically use for the rubber wood

Gizmo
Re: Trimming a Window with a Radius Top

Place the arch casing up where it goes, then trace inside and outside of the casing putting marks on the wall and jamb about where it meets the straight casing.

Then place the straight casing in its position and mark them. Now you know where the two pieces intersect. Put the arc piece back up and mark the intersection points on the casing, then take to saw and align the blade with your marks on the casing, after you get one side correct do the same for the other. Then cut the straight pieces to fit.

Its called a Hunting Miter Angle.

You can also swing the arch on a pcs of plywood laying down on saw horses then intersect the bisecting angles. Sometimes this is much easier

If the window is a half circle and the casing was made correct there should be no bisecting miter unless you want to bevel the joints together. If its a eyebrow,elliptical arch then that's another story

Ernest T
Re: Trimming a Window with a Radius Top

It's an arch, not a circle so it looks like I'll have to figure it out like you suggest. Thanks

Re: Trimming a Window with a Radius Top

Gizmo nailed it!
well put.
-Newton Carpenters

Gizmo
Re: Trimming a Window with a Radius Top
Ernest T wrote:

It's an arch, not a circle so it looks like I'll have to figure it out like you suggest. Thanks

Arc, circle, or 1/4 circle works the same way there are intersecting points that need to line up. Why don't you tack the radius/arc trim up then hold a level horizontal across the window from left to right then scribe the top or bottom of the level onto the casing. You will need to freehand the cuts in the saw when you line up the points.

Keep your SKINNERS away from the saw blade or there history

http://www.trimster.com/installtips.asp

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