TORSION SPRINGS

This chapter will tell you how to make torsion springs. Before you start, read the section on The Setup, and have your setup done (spring coil diameter correct).

Don't forget that torsion springs come left-handed and right-handed. Be sure to make your setup for the correct hand. If you're making a left-handed spring, remember that the setup and the motion of the chuck and arbor will be OPPOSITE to what is described.

Wire length

When you're ready to start coiling, the first thing you need to do is figure out how much wire you'll need to make your spring. Here's how:

Take the outside diameter of the spring and multiply it by 3.3.
Take the result of this and multiply it by the number of coils in the spring.
Figure out about how much wire you'll need to form each end. Allow a couple of inches on each end to grab onto when making your bends. Add those two numbers together.
Add together the results from steps 2 and 3.
Add in a fudge factor (about 10%, but not less than 6").
Write the result down. If you're WAY off, you can save yourself a lot of wire by cutting it closer. By writing down what you think you'll need, you'll know how much you can change this figure and still have a margin for error. When in doubt, err on the side of safety and plan to use more wire, rather than less.

Coiling the First Trial

Now you're ready to actually start.

Cut yourself a piece of wire to the length you figured out above. Be sure that anyone else in the area stays out of danger while you do the rest of this. Also, get your oven heated up.
Put the wire into your setup. Let the "front" end of the wire stick out beyond the pickup pin for as much as you need to form the SHORTER of the two ends.
It may be that your short end will need more wire than will clear the ways of your lathe or (if you're using a hand winder) your workbench. If this is the case, you can bend the wire by hand so that it will clear and then straighten it out by hand once the coiling is done.
Move your wire guide to the left as close as you can to where the pickup pin is, but not so close that the pin will hit the wire guide as it comes around on its first pass.

Your setup should now look like this (these diagrams will show both a hand-held wire guide and a tool post-mounted wire guide):

READ THE NEXT STEP ALL THE WAY THROUGH BEFORE YOU START IT.
Start your coiling. Move the chuck DEAD SLOW until you have completed your first full coil. When you have your first coil laid down on the arbor, you'll then need to do two things at the same time.
1. First, bring the wire guide a little to the left. You want there to be a gap between the first two coils as the wire lays down on the arbor, but you don't want the gap to be big. In fact, the smaller, the better, as long as it's always there. The gap should look like this:
2. Second, start counting your coils. Count "one" each time the pickup pin passes top dead center. Stop winding when you've wound one coil MORE than your spring should have when finished, or when you run out of wire. DON'T LET THE "BACK" END OF THE WIRE PASS THE PIN ON THE WIRE GUIDE!
When you've stopped coiling, mark the top of the chuck with a chalk line, and write (on the chuck) the final coil count. You can rig up a pointer out of tie wire that will indicate when the chuck reaches the exact stopping point as marked by the line.
Back off the chuck SLOWLY until the spring is loose on the arbor. Don't let the pickup pin or one of the jaws of the chuck catch on the front end of the wire and start to "unwind" your spring! When the spring is loose, slide it off the arbor and cut the excess off the "back" end, leaving yourself what you need to form the longer of the two ends.
Put your spring into the oven and relieve the stress. For this trial, you can leave it in the oven for half an hour: all you want to do is make sure you have the right diameter.

The process of baing out the stress in the wire may change the dimensions of your spring. Stainless steel coils will generally expand slightly when heated: music wire coils will generally contract slightly.

When you've finished this process, let the spring air-dry and measure it to see how close you came to what you want. Check the diameter first. If it's not OK, don't bother going any further: you'll need a different arbor, which will change all the rest of your dimensions.

If the diameter is OK, count the number of coils in your spring. You should be pretty close: if you're only making one or two springs, being an eighth of a coil off either way is OK - you can always strip out or add a small amount of coil by hand. If you're more than an eighth of a coil off, figure out how much more or less you need and change the chalk mark on your chuck so that the next time you wind a spring, you can stop coiling at the right spot.

Lastly, look at the coils themselves. They should all lie flat against each other, all the way out to the ends of the spring body. If you see gaps in the body of the spring, that means that you let the wire guide go too far to the right while you were coiling. If you see a gap at one end (usually the "front" end), that means that when you started coiling, your wire guide was too far to the right of the pickup pin.

Finally, set this spring aside to use in setting up for bending the legs. If needed, repeat the coiling process again until you get what you want. At this point, you're ready to begin work on the ends.

Torsion Spring Ends

When you coil your springs, it's a good idea to wind up a few extras so you can practice making whatever bends you need to the legs. When you have one spring that's exactly what you want, bends and all, stress relieve it again, doublecheck all your measurements, and, if possible, test it where it'll be used. Then, make all the bends in as many springs as you need.

Take the extra springs to figure out how best to form the ends the way you want them. There are a million different ways to form the ends of torsion springs, so what this section will tell you is general principles to follow.

Start with straight ends. If you're using light wire, the curve of the coil will probably make the ends of your springs curved. The curve is called "cast". You can straighten it out by running the wire over your thumbnail or by bending the wire in the direction opposite to the cast by hand.

Heavy wire usually doesn't have this problem, unless it's stainless steel. To straighten heavy wire, secure the spring in a vise and use a pipe for leverage, straightening the wire by hand a little at a time.

Make your bends gradual. This is the difference between a gradual bend and a sharp bend:

A sharp bend may cause the wire to break when a load is placed on the spring. As you figure out how to form your ends, keep this in mind. The best tool to use for light wire is round-nose pliers.

Always relieve the stress in your springs again after you form the ends. A second stress relief won't likely change any dimensions, but it will allow the bends in the formed ends to stay in the shape you put them in when they're under load.

Easy Bends:

Here's a quick way to make torsion spring ends. It's not too precise, but then again, maybe your spring doesn't have to be, either.

Find a rod that you can use to make the bend. Try not to have it skinnier than twice the diameter of your wire.

Mount the rod in your vise, along with a pickup pin. Put the end of the spring between the pickup in and the rod. Measure the distance so that when you're done, it comes out right.

Using a wire guide or a bending pipe, bend the end the way you want it. (With very light wire, you can do this by hand.) If the spring slips as you bend the end around, put some pressure on the coil body so that the pickup pin grabs it solidly.

If you're just making a few springs, you can probably get away with doing each one by hand.

If you want to make a lot of the same kind of spring, go ahead and make a more sophisticated bending jig - see the section on tooling for how to do this.

Extended hooks

If you're making an extension spring with extended hooks, like this:

you'll need to treat the ends as if the spring was a torsion spring.

The first step in forming extended hooks is to make sure that the ends of the wire are straight. Having done that, the next step is to lay the ends over. Here's how you do this:

Take the narrow plate with the knife edge that you made when you were making tooling and shove it in between the coils of your spring, like this:
Put a spacer plate the same size as your wire across the bottom of your spring.
Put the layover plate you made across the end of the spring, a little below the center of the coil. At this point, the spring and the three plates should look like this:
Chuck the three plates - with the spring, if possible - up in a vise.
Using your hand (for light wire) or a pipe (for medium wire), bend the end of the spring down over the bending plate. While you do this, hold the spring down with your other hand so that it doesn't pop off the knife plate. You'll need to bend the wire MORE than 90 degrees to get a 90-degree bend.

The two most common bugs that happen when doing this are A) the end comes up outside the coil and B) the end hooks in toward the center of the spring.

To fix these errors, A) raise or B) lower the spacer plate.

This procedure will give you ends that come straight off the ends of the coil, and fom here you should be able to form hooks or loops, as you wish.

Forward to Finishing.