Sometimes when I’m building a project I run into a problem where I can’t find just the right spring. I make the rounds of the various hardware stores and all the springs are too big, or too short, or not stiff enough. I could order some, but that’s a big delay, and once you add shipping the springs are going to be kind of expensive. That’s when it’s time to make a few springs. It’s fairly easy to wind springs on the lathe, and you can make them long/short fat/thin. I wind mine out of Piano Wire, and they work fine. commercial springs are going to last longer so for things that are going to be cycling constantly use the commercial ones, but for the kinds of things I do it’s handy to be able to make your own on the spot.
I recently had to make some compression spring for a Gong Ringing Robot, and I took a few pictures to show how it’s done. You need a way to tension the wire as you crank, so I made this little holder by drilling a #47 hole in a 1/4-20 bolt and then tapping a hole in some square stock so I could clamp that in my tool holder. I added a plastic washer and a 1/4-20 nut that could be adjusted to put some tension on the wire and put some tension on it. The whole bold floats free in it’s threaded hole so it’s naturally tracks at the angle the wire wants.
To wind the spring I just bend the end of the wire so I can tuck it between the jaws on the lathe. A somewhat acute angle is better to cut down on slip out. Then I crank the lathe by hand to put a couple of turns on the rod. Then you engage the half nut so the wire is fed evenly down the rod, just like when threading with a single point tool. When the spring is long enough you disengage the half nut and do a couple more turns to form the other end of the spring.
Don’t do this under power. A whipping piano while will cut you badly. I always wear a face shield even while doing it by hand. Clipping the piano wire with some diagonal cutters is fun because it sometimes shoot a few sparks. (I guess due to the carbon content of the wire.)
For small springs like this where the rod I’m winding around is thin, I hold the other end of the rod in a Jacobs Chuck in the tailstock. I don’t have one that rotates freely, but if you just use the normal one and loosen it up so it’s not clamped on the rod, the rod is fee to turn, but the jaws support the rod so it doesn’t deflect.
How do I crank my lathe by hand? You can of course just twist the chuck, but long ago I cast this hand crank. It goes into the head stock of the lathe, and expands to clamp in. Then I can crank away with style. After clipping the springs free, and grinding the ends flat, I usually stick them in the oven at 400 for 30 mins. That’s supposed to relieve some of the stress put into them when winding them. Here you can see the final springs just before I wrapped them in Aluminum Foil and stuck them in the oven.
Just a few final notes. Make sure not to nick the springs. That will make a horrible stress riser and the spring will eventually fail a the nick. Don’t try winding a bunch of springs in one go starting and stopping with the half nut, and cutting them apart later. That seems like a good idea, but trying to adjust things to be able to re-engage the half nut in the middle of making springs makes for sloppy springs. I made these springs form $1 worth of piano wire, and maybe an hours worth of fiddling, but that included building that 1/4-20 wire holder. I used to just tension the wire with a Jorgensen Clamp, but this way gives smoother starts/stops since the place I’m holding the wire is closer to the rod it’s winding around. Normally it only takes a few mins to wind some springs. (Not counting time in the oven)