Hi all,

How does one attach a photograph in Google groups?

I may have found an answer to my question. First of all, both Lee Spring and Century Spring are prohibitively expensive. I just checked their *stock* springs and they are ~~$1-~$2 a pop. No way. I'm looking for something in the range of 10-30 cents per spring.

So just for fun I drilled a stepped hole in a block of aluminum and stuck a piece of 0.188" OD spring in the hole, and used a tapered center punch in my drill press to open the spring up. It immediately collapses. In the larger part of the hole, it can fall out, and in the smaller lower portion of the hole where it's constrained, the coils fold in. No good.

But it happens that if I turn the drill press on, the friction between the
punch and the spring tends to unwind it, and it opens right up to the OD of the punch. I was able to open the spring up to ~0.230 OD at the widest. So, with a properly shaped taper (or perhaps 2 or three to carry out the operation in steps) I think I can open the spring up to the shape I want.

I have before and after pictures I can post if I can figure out how.

Dan


On Tuesday, January 12, 2016 at 1:38:28 PM UTC-5, Daniel Koller wrote:
Hi all,

I've certainly browsed here in the past and I am hoping that someone can offer me some relevant advice, and that this group is not too corrupted by all the political messages I just saw.

I would like to make a spring, actually, about 200 springs. They need to be extension springs, about 1" long and 0.25" diameter, but tapered so that they can be fit into an Approximately 0.23" diameter hole and will go only half way through. The upper part of the spring will stick out of the hole and will serve as an electrical contact for a wire just as in the electronics kits of yore.

I need these to be inexpensive (Less than about $0.20 per spring), because I need a lot of them. If someone knows of a source of custom springs that can make these, please let me know, and the rest of the discussion below is moot.

Because they need to be inexpensive, I am thinking the way to go is to buy uncut spring stock from McMaster-Carr (e.g. this stuff: http://www.mcmaster.com/#9664K47) and cut the pieces into 1" lengths.

But, can I taper them myself? My thought is to make a jig in a drill press. A 1" length of spring would be dropped into a tapered hole. I would then press a pin down the center of the spring to expand the top half into the tapered hole. I would then push a semi-circular slide into place to retain the spring and slide it off the pin as I pull the pin back up. The enlarged portion of the spring would be at most 0.5" long, though probably closer to 0.375" long.

This scheme seems to me like it might work, but I have a few questions.

1) Has anyone done something like this before?

2) I presume the taper has to be a little bigger than the desired ID of the spring, as it will spring back a little bit. How much bigger?

3) Does anyone have suggestions on a nice way to cut the spring to length so I don't have sharp edges that cut fingers?

4) What spring material is most amenable to post-forming?

Thanks, and I look forward to the group's helpful and imaginative responses.

Dan