Intro: Scroll Saw Jig for Cutting Jump Rings
My son volunteered to teach a basic chainmail workshop at a family camp. He had two hours and wanted to give the students ready made rings - but it's no fun to cut so many rings by hand. A search online showed many variations on cutting jump rings with a jeweler's saw and variations on using a rotary tool/flexshaft with a circular jewelry blade and some kind of jig to hold the coils steady for sawing. Well, we don't have a jeweler's saw or small, very thin rotary blades... but I have my trusty RBI Hawk scroll saw. Mmmmm. Here's what I came up with using stuff from the garage: This is faster than handsawing jumprings, but not as fast as a dedicated rotaty saw jump ring cutter.
2 x 4 inch lumber scraps (2 x 2 inch or similar also works)
drill bit gauge
fine toothed scroll saw blades (varies with gauge of wire used, but something like 40 - 60 tpi should work - thinner kerf is better)
metal rod to use as a ring mandrel - I used 1/4 inch metal rod and 3/16 inch brass rod
non-ferrous metal for making rings - I used 17 ga. aluminum wire for electric horse fencing - $22 for 1/4 mile spool of wire.
drill press or hand drill
drill driver to help speed up coiling the wire
small wood dowels or skewers the same size as the coil mandrels.
Wire of your choice: Any non-ferrous (no iron or steel) wire should work, but test a small sample before you coil up tons of rings.
Standard SAFETY warning: be careful when using sharp tools and power tools.
Step 1: Wrapping the Wire Coils
There are many ways to get wire coils, you can find lots of ideas online. Here's a summary:
1. Hand wind wire around a rod of the desired size - you can use metal rods, metal hole punches, plastic pen barrels, knitting needles etc. Wood dowels and skeweres don't work that well because tightly wound wire can crush the wood and get stuck on the dowel.
2. Hand wind wire on a crank style mandrel - this is easier on your wrists.
3. Insert rod into the check of a and electric screw driver or drill. Wear gloves to protect your hands and guide wire onto the slowly spinning mandrel. Use scrap lumber with a hole drilled in one end to support one (or both) ends of the mandrel as it spins. My son has strong hands and loves to use the cordless drill driver to wrap coils - I like to hand wind coils.
Step 2: Make Your Cutting Jig
1. Determine the outer dimension of your coil - this varies with mandrel size and wire gauge. You can use a calipers to measure, but I find it easier to use a drill gauge and stick the coil trhough holes in the drill bit gauge. Find a hole that the coil just fits through - this is the size drill bit you will use for your jig.
2. Draw a line about 1/8 inch away from the edge of wood - along the longer side of the wood. Mark spacing for coil holes - this varies depending on size of coils. You want at least 1/8 inch between the EDGES of the holes. Mark the centers of the holes to drill. You can eyeball this , or calculate and measure (center spacing = diameter of hole + inter-hole spacing;
3. Measure thickness of wood, subtract at least 1/8 inch = depth of holes to drill. Mark hole depth on the drill bit with a pieces of masking tape, or use the depth gauge if you have a drill press.
4. Drill holes on center marks. Make sure you do not drill all the way through the wood!
Drill screw holes if you want to have a bolt on top to secure coils in the jig while you are sawing. I used machine screws and thumbnuts.
Step 3: Cutting the Rings
This method works best for 'score and bend' ring cutting. Cut the rings almost all the way through the coil, remove from jig and snap the rings off at the scoreline. (If you cut the rings all the way through, they can jam the scroll saw blade in the jig and bend or break the saw blade).
Cut coils to fit into the jig
1. Insert coil into the jig hole and press it down into the hole
2. Take a utility blade and insert it one coil above the top surface of the jig
3. Carefully bend the coil to the side.
4. Remove coil and cut the measured part of the coil just below the bend. Trim edge flush to the top of the coil.
5. Insert coil into the jig hole and make sure it sits almost flush with the top.
6. Repeat for all holes.
Screw top down using thumbnuts. OR use masking tape to secure wood to hold down the coils OR use a nail or metal rod to hold the coil down while you cut the coil.
7. Insert fine tooth metal blade into the scroll saw (40-60 teeth with as small a kerf (blade width) as you can find.
8. Start from the outer edge of the coil and make a straight cut towards the center of the coil. The first time you use your jig, you will cut through the wood before you reach the metal coil - see the marked lines in the 3rd picture below.
9. Make sure that the coil is secured so it doesn't bounce up and down as the scroll saw blade moves up and down - the coil should be held down by the wood cover, or maually held in place using a thick nail or piece of metal.
10. Saw almost all the way through one side of the coil.
Note: Thinner gauge wire may need to be supported by a wood dowel or skewer placed inside the coil.
Saw SLOWLY, applying a smooth, even pressure - go SLOW and let the blade do the work of cutting, do not push hard or you will snap the blade.
Step 4: Snap the Rings Apart
1. Remove coil from cutting jig
2. Firmly grasp coil in your hand, bend the top ring out (away) from the coil, until it snaps at the saw line. Stiffer wire will snap better, while soft metal may twist and kind of tear away from the coil. Use a pliers if you need to do grasp the rings.
If your saw cut is not deep enough, you may need to 'help' the ring come off the coil - use a fine wire cutter as needed.
3. Inspect the rings and make sure there is no sharp burr on the end of the ring. If there is a burr, you can file it away, or tumble all the rings in a rotary tumbler with steel shot and a little soap.
4. Make stuff with your rings.
If you really like making chainmail, explore faster ring cutting methods, such as the Jump Ring Cutter http://www.contenti.com/products/saws/400-125.html