Arched Moulding Glue-Ups
Advice on sawing thin strips and gluing them up for arched moulding blanks. July 22, 2013
Question
So we're finally in the arched/curved molding manufacturing business. We have clamps, forms, Mikron, etc. How do you guys rip your strips for gluing and bending? Normal table or rip saw, then plane on a small planer? What is the best sander for the edges of the bent, molded product to uniform the width and pretty it up?
Forum Responses
(Solid Wood Machining Forum)
From contributor S:
We have been making arches for about a year now so I guess I am still in the learning stage also. We rip our strips on a straight line rip and then run through our s520 planer or the Timesaver, depending on the thickness and the material. We usually only hit one side just to get the thickness even all the way through. It was a trial and error process but now we know the thickness of the strips to come up with the different final widths. The degree of the arch affects the thickness of the strips. Then we glue and clamp, plane down to a couple of thousands over our final thickness, then run through the Stegherr, put the relief in the back, and finally just hit with the Dynabrade and we are done. Also, make sure you staple a strip across the bottom so the arch does not unsparing before finishing. What kind of clamping system do you use?
From the original questioner:
For a clamping system we use a 3/4" sheet of ply/osb, 6x6x.5" steel angle cut into 1.5" pieces. We use Bessey Stairway clamps and an impact air wrench. It works well.
From contributor S:
Clamping sounds identical to what we use. On really tight radius arches I cut a plywood form and use a piece of steel banding and a banding tool. That works really well but takes two or three people to make it easy.
From contributor D:
It seems like a lot of work, bending cold and waiting. About 75% of our casing is solid, bandsawn. A typical opening gets three pieces left extra-long. The few customers who want one piece casing from veneer stock we use a PT-6 radio frequency laminater. Veneers for these are sawn with an orbital frame saw with two minute glue-ups. Bandsawing blanks takes not much longer if you've been doing it for a while. An edge sander sits next to every bandsaw in our shop.
From contributor S:
What kind of joints do you use on your three piece arches? If you have an RF press I am sure you do way more than us. We maybe do 10-20 a month and have it down to about 45 minutes to do one. I know we are not setting any records but for the quantity we do we can't afford to spend a ton of money on equipment. Our main focus is running trim through the Weinig and cabinets.
From contributor D:
We just butt joint them. Most windows and doors are sold with exterior casing applied, and interior kit is loose. We also bend one piece vinyl casing if they want it, by heating it up in long ovens. They come out limp and form easily around templates, which are just bandsawn scrap quickly stapled together on the floor. We do keep several hundred commonly used size templates on hand as well. We manufacture the most elliptical windows in the eastern U.S., but nearly all units are one-off custom for front entries.
From the original questioner:
What are you guys using to true/size your blanks after arching (either by strips or pieces), to get it to an exact width for the molder. Are you using a sander and what kind? I have a Mikron with the router attachment if it helps.
From contributor S:
I do not size, I adjust the width of the blank before gluing. Just adjust the thickness of your strips to achieve the final width you want. That is why I plane or sand them before that way the width is consistent throughout the blank. Does that make sense?
From contributor D:
We still largely bandsaw casing blanks. We have fathers, sons, brothers, etc. who are masters on the bandsaw. Some have been here twenty years and have never worked anywhere else. Jambs are now almost 100% done on the PT-6. Rare knockups for weird radii where it takes longer to program the machine get stack lammed from bandsawn stock. Contributor S mentioned 10-20 per month. In our heyday we had 40 employees. Bare minimum each had to build ten elliptical and/or segment direct set transom windows with varying jambs, casing, dimensions, etc. in an eight hour day.
