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How to trim an arched window

52K views 32 replies 21 participants last post by  tccoggs  
#1 ·
I got a side job doing trim on a unfinished house but the trouble is that I haven't had to do an arched opening. The trim is to be MDF 2 1/4 ogee Base/Case. What would be the best way to try to bend it. Thought about relief cutting the bottom which would become the top to create a fan. Suggestions please.
 

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#7 ·
just make it yourself, don't try and bend it, just get a wider piece and draw the arch then cut and router it. I've made many arch pieces. one time I had to make a large one and used two pieces of the trim specified and ripped alternating pieces (to make up for the saw cut) and glued them all back together in the arch. It was getting painted so you never saw the pieces. Had to do that twice in the same house, one bigger than the other.
 
#14 ·
I tried using a piece of pvc trim for a similar window a few years back. With some effort, I got it to make the curve. The first nail caused it to explode into a million pieces. Really scary.

Started over with flex trim after learning what didn't work.
If you're bending PVC trim, you should use a heat blanket to soften it enough to make the curve, or make it out of sheet goods, like I do.:thumbsup:
 

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#33 ·
You just need one of these

Image


Leo has a thread on curved moldings you might want to look at http://www.contractortalk.com/f13/curved-moldings-74133/

Personally, I would not attempt it myself. I would refer them to someone who does custom millwork, you want them to have it done the right way.
WH is a great machine for the money but at some point you get past what it can do. Then look to a US Concepts machine:

http://www.usconceptsinc.com/archMoulder-fas-hd.cfm

Or for even higher volume, a CNC with a dedicated 10HP horizontal molding head like a Komo Mach 3 or Northwood Machinery. You can make complex profiles on just about any CNC using multipass, but the program can be complex, and it takes alot of machine time:



http://www.woodweb.com/knowledge_base_images/zp/radius_moulding_machinery_choices.jpg


I would love to find a video of the komo in action. Since it used the same corregated back knives out of a Wienig/Wadkin feed through moulder, your straight profiles always matched the radius. With a dedicated 10HP spindle, you could run 9 inch wide profiles. For paint grade we used to cut them out of rangerboard MDF, so there was no glue up time, and Azek sheets for outdoor stuff.
 
#15 ·
Here's how I do them. Just a router and a home made base for the router. I've done wall plates with 3/4 plywood the same way. 16' radius is the largest I've done so far. Just have to extend the base using 6" wide rips of plywood.:thumbsup:
 

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#17 · (Edited)
On curved trim, we usually get it made at a custom millwork shop. Just have to give them the radii and a trim sample.

I did make a few casings in my own house, very much like the window in the opening post, but I used sanitary trim throughout.:shifty:

I apologize for the quality of the pics,. I had the wrong film in the camera. These were taken the day I sold the house.:sad:
 

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#18 ·
I wondered why they didn't order a trim kit with the window.

It's just a single ogee I might attempt to make it. Flex trim dose sound like it would work. I'll do that window last but will have to address it first with the HO to figure out which way he wants to go. Oh and he needs to rent the scaffolding for me to put it in too. Thats not going in off a ladder thats for damn sure.:laughing:
 
#19 ·
Here's a video of cutting radii with a router. I only used one radius on this setup because the inside curve was the only one that mattered. You can use as many center lines as you want and change bit profiles to flute the trim, etc. These were being used to make bending forms for drywall, so I whipped them out pretty quickly.:thumbsup:

http://www.youtube.com/watch?v=f-uZRuz4P0I
 
#20 ·
Here's where the got used:thumbsup:

I also made some ramps to bend an arch across the sheets, using a combination of the router for the radius and a Skilsaw to make the straight cut.
 

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#23 ·
Hardly Working,

We're both in Seattle, if you're interested you can come over to my shop and I'll show you how to make up the jamb and trim as a joined unit. Then it can be placed and nailed off fairly easily.
Keith

I'll take that offer to stop by your shop. Your work is something to admire.

What's your location? I'm now on the eastside in Jaunita.
 
#27 · (Edited)
Hardly Working,

I'm located on West Marginal Way, near Georgetown, about 45 minutes from you.
A couple of things you'll need first.
Determine your reveal. It will be the same as all the other windows. Measure from reveal to reveal where the transition occurs from straight to curved. Next measure from the center point to the apex keeping the same reveal. You will need a piece of the molding. If it is flat then you're home free. If profiled then you will need a knife to make the profile. I have a Woodmaster, making the profiled trim is very straight forward.

I'll be in the shop most of the week, give me a call.

A number of people have asked about the shop over time. I have the beginnings of a decent shop. It's not yet finished, don't know that it ever will be... That said I've seen outstanding work come out of garage shops and crap come out of 20,000 sq foot shops. The most important part is the person who does the work.

Bconley,

My hat is off to you. I lived for several years in Tacoma, never had a single job there. Everyday I drove to Bellevue, Seattle, Mercer Island, Kirkland, etc...
 
#28 ·
use flex trim ....because the radius in your pic is more of an ellipitical than an arch they will need a template ...millwork company will come out and make or make it yourself ...take a piece of red rosin paper or any kind of paper that is as wide as opening and tall enough to catch the radius ....tape or pin the paper to each side of opening and use a pencil or crayon and just shade over the opening along the edges ...like you did with coins as a kid ...make sure you get about 2-3 inches of the leg or jamb as well as the radius ....take it to your supplier and have them send it to the numerous flex mould manufacturers and in about 2 weeks you will have a piece that matces that opening exact ...if you have multiple openings and they are the same width but different radius (even an inch or so) you will need multiple templates...
 
#29 ·
I'd rather cut the trim from sheet of PVC or MDF. Or even take the time to rip and glue the trim than pay close to $150 for a 12' piece of crap trim. Then I bank the difference for my time.
If you're really backed up on work then I'd use the flex trim. I'm not.