The shield press
I wanted to make several shields, and decided that the first thing I needed was a shield press. I already had plenty of 2x4's and plywood leftover from a previous project and this is what I came up with. It works very well, and makes short work of bending a couple pieces of 1/4" plywood. This will makes shields up to 26" x 47" (you could possibly go wider but I have not tried this and it may be hard to bend).
I must admit this may seem more complicated then some of the other shield press projects I have run across and I will agree. My goal was to make a press that made very even bends, did not impart waviness to the edges, and produced a truly circular curve to the shield. It is simple to use and produces consistent shield blanks. This is not to say, that my shield press is better or worse, it is just what I came up with and it works well for me. They all pretty much work the same way, hold the plywood pieces in a bend until the glues dries.
This project shows how to build the press and how to make the shield blank. For instructions on actually building the shield you can go here:Shield Project page.
I attempted to come up with sort of snazzy clamping system, but after trying some different ideas, I went with
tie down straps. They work very well, and make short work of bending the plywood. I use 4 of them. I also use 5
pieces of 1x3 4 ft long to give the straps uniform pressure on the plywood. I can glue and clamp a shield
in about 15 minutes.
You may notice that I have already drawn out the shield design on the plywood before I bend it, much easier!
The plywood you want to use is a standard AC or BC 1/4" plywood. Do not attempt to use a hardwood plywood, such as birch or oak, they will just not bend much as they are much stiffer. When the two 1/4" pieces of the plywood are glued together they make a pretty tough piece of curved 1/2" plywood.
This is just another shot of the press while clamped down. At this point the straps run all away around the press,
but it would easy enough to figure out a way to permanently attach the tie downs to the 2x4's on the side.
You can also see some good construction detail here. The board you see here with the screw holes is the 1x3 side clamp, which has a 1/2" spacer beneath it.
The two pictures above show the finished shield press. I include these so you can compare them to the plans below. Hopefully with
these pictures and my plans below you will be able to put this together without too much trouble. (Note: I have since
increased the size of the ribs from 4 1/2" shown, to 6 1/2" for more bend, the rest of the plans here reflect this change).
Steps to build
The first thing you will want to do is to cut the 2x4's and assemble them. You will need to cut 2 of them 48" long, and then 6 2x4's 24" long, this will give an overall width of 27". I actually like using screws to pretty much assemble everything, I seem to get more accuracy, and of course, less "pull-apart".
You will now want to cut out the 7 curved ribs. I used 3/4" x 1x8 pine board for the ribs. I used a long string nailed at one end, and a pencil tied at the other end to get the radius.
Next you will need to cut out a piece of 3/4" plywood that will serve as the base for the bending boards and the base of the 2x4 frame. This piece will need to be cut to 27" x 48". If you happen to already have a 2'x4' piece of plywood, you can use this and add another piece 3" x 48" to finish up. If you look closely at mine you will see that is what I did.
Now you will attach the curved ribs to the plywood base by screwing into them from the bottom. Be sure to pilot drill
first so you don't end up splitting the pine ribs. I also used glue here. Just make sure they are somewhat
After you have all the curved ribs attached to the plywood base, you attach the plywood base to the 2x4 frame using screws.
Whew!.. almost done! The last step is to attache the 1/2" spacer and the 1x3 side clamp board. I used a piece of oak here for strength. The plans below and pictures above should show where and how this goes on.
Ok, you now have your own shield press. You will also need about 4 or 5 1x3's for clamping support that are 48" long, and some ratchet type tie downs..
You will need 2 pc's of 2x4 1/4" plywood and some wood glue (I use titebond II). Even though plywood is made up of
different layers of grains running opposite directions it still has "grain" to it. Plywood bends more easily in
one direction then it does in the other. If have to cut a piece or get one cut make the top grain runs as shown
To spread the glue it nice to have a short bristled brush. I just make my own by getting some cheapie bristle paint brushes (1 1/2" brush) and cutting off all but about 1/2" of the bristles. This makes a nice stiff brush to spread the glue.
Most plywood has one good side and one bad side. You will want to have the good side on each piece of plywood to the outside. It is much easier to draw your shield design on the plywood while it is still flat. For best results do not design the plan so that it goes all the way to the edges. In other words I wouldn't make a shield any larger than 23" x 47" for a piece of 2' x 4' plywood. For some ideas on actually building the shield you can go here: Shield Project page.
The picture below shows 2 shields drawn on piece of the 2' x 4' plywood. These measure 22 wide by 23 tall. They don't quite follow the 3 to 1 unit method mentioned in the shield building project, but they are close enough.
I always use my press sitting on the floor. I go ahead and have the straps wrapped around the press and ready to go before I start the gluing.
Next you will want to spread a coat of glue to both insides of the plywood pieces. You don't want to spread the glue paper thin, but it doesn't have to be a really thick coat either. The below, left picture shows the glue applied to "bad" side of the plywood. After the glue is applied to the first piece of plywood go ahead and place it in the press. You may notice that I have tucked some wax paper into the grove. This makes sure that I don't glue the shield to the press.
The picture, above left, shows the second piece of glued plywood place in the slot and on top of the first piece I had already inserted.
I know place the clamps around the plywood and snug them down a bit. I then insert the 1x3's x 4' under the strap and space them evenly around the plywood. I now ratchet the clamps until they have almost pulled the plywood into its curve. You may need to adjust the 1x3's again. The last 1x3 (opposite of the slot), will need to be hammered a bit so that it overlaps the edge of the plywood a bit. Now finish ratcheting the clamps until the plywood is bent to conform to the curved ribs. I always tighten them evenly as I ratchet them. The picture, above right, shows the press all clamped and ready to sit for a couple of days.
Check out the two graphics below for some more detail.
The picture above shows the clamping action up close. As you can see the curved ribs cause the plywood to curve very evenly. No lumps or waves!
Below is a picture of the plywood removed from the shield press after they have dried. They are now ready to be cut out. Be careful when cutting across the grain with the jig saw. Go slow so you don't splinter the wood.
To see more detailed instructions on building a shield go to my shield project page
|Home||Projects||Photo Gallery||Contact Me||About Us|