Cutting dies are expenive to have made professionally for a custom application, and oftentimes it just seems easier to cut with an exacto knife than get a die made, especially if you will be making an unknown quantity of items. Depending on the complexity of your design and how precise your dimensions must be, making your own die can save you quite a bit of time and effort. If you must have ultaprecise dimensions, this method is not for you, but if being off by 3/32 won't cause the sky to fall, making your own cutting die is a straightforward process.
This die is designed for cutting paper. If you want something that you can put in a press and stamp thin sheetmetal with, you will need to use a different source for the blades (actual sheet or flatstock, not just the trash from last night's chili), and you will need to set these blades in wood or metal. If it's metal, tacking them in place with your arc welder is a good idea, but you will need to run a full bead (or braze) before you apply 12 tons of force. If you are building a press die, you will also need to get a small square, to make sure you have your blades at the right angle. For just cutting paper, it's nowhere near as tough, and that's what we'll be doing today.
Don't be an idiot like me and forget to sharpen all your blades before you bend them and stick them in tight corners. I have not actually sharpened this die yet, and if/when I do, I will update this with photos. Until then, you get a verbal description of what to do. It will work.
Step 1: Get your materials
-- You will be needing a block of floral foam large enough to fit your whole pattern on.
-- One or two metal food cans (empty them first. Yum)
-- Tin snips (don't just try big scissors
-- Gorilla glue
-- Needlenose pliers
-- Leather gloves (optional, but there will be edges ranging from kinda sharp to razor sharp)
-- Dremel tool or handheld drill (no drill press), or even a bench grinder if you are so lucky
-- Clamps or a vice (to hold things while you sharpen)
-- Grinding/sharpening attachment for your electric spinny thing of choice
-- A flat object big enough to fit over your entire pattern
-- Ruler or calibrated eyeball
-- Time and the patience to use it
Step 2: Cut up your can
You want to cut your pieces about 3/4 inch wide, and however long you need for that section of your pattern. Try not to have a junction between blades in the middle of a curve, but if it's unavoidable, it can be done cleanly with a little dilligence.
Step 3: Sharpen your pieces
This is the step I forgot.
You want to get these exacto-knife-sharp. Put your blade (before you do any bending it might need) in the laws of a vice. Get out your grinder/sharpener and grind a sharp bevel on one side of the soon-to-be blade. You want a very low angle, not a wide one like on a chisel. If you have an actual exacto blade, use it as an example.
Do your grinding with little pressure, and make sure you don't stay in one spot too long. The last thing you want is a hot, soft blade. You could try warming it with a torch and tossing it in used motor oil, but I never saw the need.
When you're done, take a whetstone (or fine-grit wetsanding paper in a pinch) and run your newly created blade across it a couple of times, beveled side down, then flip it over beveled side up and do the same thing. Sharp endge leading. Now test it on some paper. If it cuts more like an exacto than a steak knife, you're ready to move on.
Step 4: Start laying your die
You want to start laying out your pattern (wearing gloves!) in your floral foam. You really don't want to make a hole and then have to remove the blade and make another hole with it, so make sure it'll be square and located correctly.
Start from a good reference point. In this case, I started with the back wheel, because that tells me where the axle is, and therefore the limits of where the corner of the car can be. I had to cut the piece for the wheel a little longer than I expected I would need (then sharpen, right?), and cut it to length until I had the right radius. Measure twice, cut once, unless you're flying by the seat of your pants, then just keep cutting tiny bits till it works. If you cut too much and run out of can metal, go eat a can of pears and watch NASCAR.
Note: do not use Busch's baked beans cans for this application. I know, I can see the disappointment on your face. As great as their products are, they put what looks like some sort of emamel paint/coating on the insides of their cans. This keeps the tinny taste out of the beans, but it also is a very stubborn coat of non-metal. I use these cans as storage, not scrap metal.
And no, I don't send my cans to get melted. I make all sorts of things out of them.
Step 5: Bending your blades
Depending on your design, you might need to do some serious bending to make a section of your die. If the corner is going to have to be sharper than the nose of your needliest neddle nose pliers will allow, you are gong to need to make two blades and have them meet at the corner of this sharp joint.
An example of this is in the intake stacks on this hot rod. Since this is stylized design anyway, I wasn't too concerned about precision (or even mounting the engine straight), but you can see where I made the 135 degree bend, then for the sharper corner of the slashcut, made a new blade. You can see that from the firewall to the radiator, the engine is made of three separate blades.
This is a V8 Chevy small-block. The middle exhaust ports are siamese, remember? I'd have put a Ford in a Ford, except I didn't want to make four header pipes!
Step 6: Set all your blades to the same height
This is ultra-high-tech. Set your large flat object on your newly created die and lean on it. Be careful of pressing the blades too deep, and make sure it's parallel to the foam surface.
Step 7: Glue
Not that much glue. Seriously, less than you think. No, even less. A little... no... there you go. That should be plenty. Really.
You want your Gorilla glue to expand and harden your foam, as well as reinforce the blades from every angle possible, while keeping at least 1/8th inch clearance between the sharp bits and the rapidly expanding Blob. Unless you a are a master Gorilla Gluer, you won't quite get this right. That's okay.
If you have put on too much glue, don't do what I did and start paper toweling off the foam as it expands and threatens to swallow the table. You think I'm kidding. I wish I had photos (or even video of my panic as the glue just wouldn't stop), but I was covered in glue and didn't want my camera to share that fate. Wait until it dries and rout it out. Do this with a Dremel rotary tool if you have one. If not, that's okay, but the dremel is a heck of a lot faster because of its higher rpm.
Forget what your junior high woodshop teacher told you about routing with a drill. Embrace what your high school shop teacher told you: "go ahead, kid, try and rout with the drill press, but don't come crying to me when it doesn't work right." Maybe you never succeeded in your quest to hand-CNC a 3D B-52, but that doesn't mean you can't use a regular drill bit as a straight-cut router bit in a pinch. Use the maximum speed setting. Be aware of the bit catching a blade and kicking things around (no, shards won't fly). Go slow and gentle and you'll be fine.
Step 8: Cut
Do this on a soft rubber pad, like the underside of your average mousepad, or that craft rubber mat stuff that they have on papercutting tablets. Set your paper down, set your die on it gently, and lean on it. Make sure you've got pressure everywhere. Lift and check the results. Any spots that didn't get cut are either from a somewhat dull blade, or a gap in your blades. If it's a small gap, you can just keep an exacto on hand to cut that little spot easier than you can fix it. If it's a dull blade, there'll probably be a crease left in the paper where it should have done some cutting. Get out the ol' sharpener and fix it.