Compression spring info

woodchucker

woodchucker

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I would like to make my own compression spring, I have made many before, but never this big. I am struggling on this one.
I am going to do as in https://www.hobby-machinist.com/threads/clausing-8520-vibration.115667/post-1188818 but much bettter I hope. I see issues with that one.

So the ID of the spring will be 1.31, I have 2 coils of music wire .041 and .035. The rest of my music wire is 36" length sticks. I tried using the .041 to make the compression spring and it does not seem to hold the bend. I think because it's too thin for the size ID/OD that I need. It has worked in the past for small 1/4" id springs. Am I correct in my assumption?

I am sitting with the Machinist's handbook and don't understand it. I think it is just glossing over compression too lightly.
Also my music wire is precision brand and it's got a chart on the back that really is reverse of what I thought wire gauges would be.
I thought 3 aught would be very heavy, but the precision chart shows it to be extremely fine. The Machinist handbook, looks like a 3/0 is very heavy and requires a coarse thread.

The length of the spring will be 4.1 Inches and as I said 1.31 ID.. I only want about 3-5lbs of force.
So I think using a heavy gauge wire would be too much. McMaster has a spring in near that size but it's 127+lbs of force if I remember from the other day.

Small springs easy peazy.. large springs... :rolleyes:
 

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Totally off subject, but in times past before the advent of high-end laser levels we used piano wire at work not only to make springs, but also to level and align equipment. Depending on the overall length of the finished packaging line we would use different gauge wire. A set of known height bars would be anchored to the floor parallel to the planned location of the equipment.

The proper size wire would be selected and run between a turnbuckle on each post. It would be tightened until it achieved the proper note. We actually used a tuning fork to be sure the wire was tensioned properly. Then we could use a transit to be sure the equipment was parallel to the wire. Each piece of equipment also had a plate on either end at a known height. Once properly aligned the equipment could be leveled using the music wire and a certified 1 meter, or 1.5-meter ruler. The accepted accuracy was usually within .015" for a 60' span.
 
How are you holding / tensioning the wire as you wind? I'm thinking you're going to need a fairly tight angle between your tensioner / feed and the large mandrel in order to get the wire to take a set. So the wire is making a roughly 90* bend between tensioner and mandrel. 1.031" is a pretty precise number - be prepared to experiment with a lot of mandrel sizes if you need that precision.

GsT
 
GeneT45 said:
How are you holding / tensioning the wire as you wind? I'm thinking you're going to need a fairly tight angle between your tensioner / feed and the large mandrel in order to get the wire to take a set. So the wire is making a roughly 90* bend between tensioner and mandrel. 1.031" is a pretty precise number - be prepared to experiment with a lot of mandrel sizes if you need that precision.

GsT
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Not 90, I have an aluminum block that I drilled a hole just to the size of the wire, I allow a burr on the wire when inserting and that opens the hole I guess like a screw, it's a tight fit, plus I hold back using pliers behind the joint, where there are flats with serrations that are able to guide the wire.
it's always worked for small springs. You think I need a 90 before it goes on the mandrel?

Edit: that's the size I want, it may not be the size get. A little smaller or lager will be fine.
 
You might not need a full 90*, but I think it's going to have to be a pretty good bend. As spring diameter grows, so does spring back, so you might need a substantially smaller mandrel. You might try a 0.75" for a few coils just to see what your finish ID is. That should start to calibrate your setup.

GsT
 
GeneT45 said:
You might not need a full 90*, but I think it's going to have to be a pretty good bend. As spring diameter grows, so does spring back, so you might need a substantially smaller mandrel. You might try a 0.75" for a few coils just to see what your finish ID is. That should start to calibrate your setup.

GsT
Click to expand...
right now, in my test last night, it was not close to staying like a spring. So that's why I got the idea that my mandrel might be too big for the wire size. I'll play with it. I may have to up my wire size by a bit to make that large an ID.
 
So I think I was correct, the wire was too thin for the size mandrel. I went to a 1/2 rod and it took a set.
It also loosened back up to maybe 3/4 of an inch..
So size does matter guys. :laughing:

So when I was trying with a large mandrel, I noticed the length of music wire was over 6 ft to get what I wanted. So my short 3 ft length of .071 is not going to work. I got to thinking, and remembered I saved a garden hose strain relief. I mounted it and it seemed promising. But still too small on ID. So it had a lot of idle turns. I stretched them out for a test. Very promising. But it confirmed why the size needs to be very large id because I was not able to lower the quill as it bottomed on the coils too early to make it worth while. But I got data. The wire size of the garden hose strain relief was .076.. so I know where around I need to be.. A little larger would be fine.

PXL_20250102_025429896.jpg
 
When winding oil springs, there is always spring back so the mandrel you are winding on will necessarily be a smaller I.D. than the spring.

I used to make springs on the lathe by mounting an appropriate mandrel in the chuck and inserting the spring wire past the mandrel and between two jaws on the chuck to secure the end. To wind the spring, I would stand back three or four feet and pull the wire taut with a pair of Vise Grips. I loosened the belt on the lathe so it would slip if pulled hard enough. I made serviceable springs in that fashion. A better way is to use a tub with a small orifice at one end , The tube is mounted in the tool holder and the orifice is brought close to the mandrel. a brake pad can be used to put tension on the spring wire or you can use the Vise Grips. I also made a larger one with the brake pad and can wind .125" stainless with it.
 
My go-to for spring data is the Lee Springs catalog. I have a hard copy but they have a on line catalog. You can get data on literally thousands of springs in carbon steel and stainless.Their prices are high unless you order quantities of 50 or more but there is enough information that you can design custom springs to meet your specs.
 
That was very helpful. It got me to the data I needed about wire size. I can order the wire I need from MC for about $12, then form it.
Or I can order a spring from LEE for $18... or $30 depending on rate/inch
I'm going to have to think on that one. I like that they give you number of turns per spring.
 
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