Making a curved face frame

[AMF]

Im working on some replica "tombstone" style radios, i.e. from the 30's to the 50's. The face frame is being made frome Oak and im having problems gluing up the 4 pieces that make the radius for the face. (4 peices joined and a 22.5* mitre)

Im having problems with consistancy, I have been using a jig to glue up and clamping with wedges but I am a bit scared that the mitres and end grain arent going to hold together while I pattern rout it. Any help is greatly appreciated..

Alex

[Don]

Hey, Alex. You're facing a challenging opportunity and would benefit from learning how to make a new joint, a spline. Learning how to make this joint will allow you to make "off angle" joints like this with ease with no worry of strength or longevity.

Visit this thread; http://www.woodworkingbuzz.com/forums/showthread.php?t=234&highlight=dodecahedron to get an idea of how to do it. You will see that this assembly has many joints similar to your project, but it was all assembled with masking tape.

Let me know if you have any other questions, I'm sure others will chime in with their solutions as well. Let us know how you progress.

http://www.internetcp.com/gallery/data/503/medium/IMG_0424.JPG

All the best, Don

[AMF]

Thanks Don, the thought had crossed my mind to use splines, but Im not sure id the customer will like the look of them, either wasy ill give'm a try. Ill try to post pics later on of the frame I am making.

Alex

[Don]

With a little planning and jigging, you can also make "blind" splines. The simple way is to postion the piece on a mark on the rip fence, then raise the blade, push the part to the opposite mark, lower the blade. Will only work if the part is long enough to allow for a decent spline.

Good Luck.

[AMF]

Thanks Don, ill keep that in mind for future projects. I realized last night that I had made my clamping jig too complicated and instead of clamping the mitres I was clamping all my pieces towards the inner "fence" of the jig. I removed the fence and the mitres are great. This along with taking special care while mitering and milling have proven successful.

Thanks again, Alex

[AMF]

Heres some picks of my latest attempt.
http://i268.photobucket.com/albums/jj5/amack_photos/DSCF2352.jpg
http://i268.photobucket.com/albums/jj5/amack_photos/DSCF2353.jpg
http://i268.photobucket.com/albums/jj5/amack_photos/DSCF2354.jpg
http://i268.photobucket.com/albums/jj5/amack_photos/DSCF2355.jpg
The main issue I am having now is making the vaneer stiff enough along the curve. I may have to try a plastic laminate as a subsrate to stiffen it, unfortuatley these are supposed to be cheap and easy to build, not true! lol.

I changed the face design a little bit, at first the face frame was glued to the sides and the "face" was removable. Now the face and face frame are one and they are removable via some cleats inside the carcase.

Alex

[Don]

Hey, Alex - nice work and pics. I misunderstood what you were trying to do, the spline method would have nothing to do with what you are doing. But . . . depending on how many of these you have the opportunity to make, a simple veneer press would make the whole carcass at once. This is how they were made back in the day. That would simplify your cleat affair considerably.

If you are interested, I could sketch up a possible serving suggestion for somthing like this. You'd have an exterior of oak then multiple anywood veneers behind it. Brush it all up with a glue like Dap plastic resin and push it all in the mold. The next day you would have a formed part. This would only be worthwhile if you had more than 10 or so to make.

Other than that, looks like you've got it figured out just fine.

All the best, Don

[AMF]

Thanks Don, never even thought about making a mold for it. Im not to sure how many I have to make just yet, possibly as many as 20. The main issue I am having is making the vaneer between the cleats stiff enough, and the vaneer is also wavy complicating the finishing. Im leaning towards putting a layer of plastic laminate then the vaneer. Any Ideas?

Alex

[Don]

Hey, Alex. Yeah, if you have 20 to make then you need to get a process that you are comfortable with. First off, I'm going to assume you are working with an oak veneer, not an oak plywood. The plastic laminate idea is not a bad one, but this intimates that your "shell" will still be thin and that means that you will have to spend time making a suitable frame for each one to give it rigidity, right?

If I had that many to make and was using veneer, and did not want to spend the time to make a mold, then there are two methods that I'd use to get the carcass sides and top all in one substantial peice.

First off there is a plywood material here called "bending grade" most of the better cabinet/lumber plywood dealears supply it to your local millwork houses. This material is like a regular plywood except the outside veneer is left off, this makes the material very flexible. You can usually find it in 1/4" and 3/8" thickness. A couple rips of that stuff, glue in between the layers, bent around a simply form and the next day you have your shape ready for the oak veneer. You'd be surprised how strong this will be.

The other method is one that I"ve used many, many times to get a curve in plywood, even plywood that has the finish veneer already on it. You simply kerf "cut" the underside of the plywood on your table say. Let's say that you start with a rip of 3/4" oak plywood about 36-48" long, enough for the length of your sides and the radius at the top. The middle 18" or so will get saw kerfs about 1/2 to 5/8" deep about 1/4" apart, you'll find that this will easily bend about a simple form to allow you to shoot in the "framing" to hold the shape. Or you can glue and cover the inside of that shape with another layer of thin plywood and the shape will be strong and self supporting. You'll have to experiment with the depth and spacing of the cuts to make sure it bends easily, but does not show "facets" on the outside.

Let me know if you need a better explanation. I can see that the way that you are doing it, you'll be unsatisfied with the radius between the front and back "ribs". It will be a bit wavy and most likely will be a bit "hollow" or depressed between the front and back ribs.

The way thay made these back in the day was simple. All veneer, glue between, sandwiched into a metal mold, zapped with high frequency current, (microwaves) popped out of the mold and just a minute or so, then it was trimmed to shape.

Let me know if you need a sketch.

All the best, Don

[AMF]

Thanks a mil Don!

After chatting with the customer (who is a radio expert) we decided to try the laminate idea, and he had some leftover formica he got from god knows where. Gave it a shot to night with 4 "trusses" like in the picture, and it is very solid. I will see tomorrow what it looks like with the face vaneer on it.

I may add that we are trying to keep the costs as low as possible until he figures out if they will work out for him and are a marketable product. After that he may want more and better understand the price people are willing to pay.

I might try that plywood kerfing Idea one day to see how it will work/look. Any refernces on depth of the kerfs, I am assuming that leaving 1 ply uncut would work best.

Thanks again, Alex

[Don]

Kerf depth and spacing take into consideration three things, quality of plywood, thickness and desired radius. It's all experimentation. To many, too close, too deep and you have no strength, too little, too far apart, not deep enough and you can't get the radius you want without faceting or breaking. I'd say that for what you are doing and if you used 3/4 plywood, 5/8" deep about 1/4" apart (leave 1/4") saw kerf about 1/8". A good starting point. Try it, you'll be amazed at what you can do.

dawjr