how can i make a spring

[picclock]

Hi I need a compression spring of certain dimensions (1/4" od, 0.5mm wire , 1.25" long). The spring will only be compressed by about 1/4" so I'm thinking the easiest way to get something in this ball park is to wind it myself. I'm in the UK so I'm thinking I need a supplier of small amount of spring wire so I can set it up on the lathe and make it. 

So this is really a fishing exhibition to see if anyone here has made springs, what the snags are and who are the best suppliers of raw materials.

Hope this makes sense

Best Regards

picclock

[jonesie]

i just made 2 springs about that size, i used guitar strings. you  can get them in different sizes,and they  are also spring steel. if you google making small springs there is a good site that tells how. i am at work so do not have the site. just made one for my farm boy hit and miss and i came out real good, but there are some things  you need to follow  so you do not get hurt and they will need to be annelled.i will look up the site when i get home tonight. good luck. jonesie

[stovebolt]

 I just learned a few thing about making torsion spring, haven't tried compression yet, the links below were helpful.  Some people say the term  music wire doesn't mean it's the same as music wire I don't know,  the stuff I bought was 1080 carbon steel,  also know as music wire,  see the last link, scroll about half way down, it's a US distributor I just added it for reference.
 I heated my springs to 450F  for 30 minutes in a toaster oven,  they came out fine. 

Jim     
 



http://home.earthlink.net/~bazillion/intro.html


http://firearmsdesigner.com/?p=247


http://www.mcmaster.com/#music-wire/=l6yall

[John Rudd]

Picclock..

Check out your local model shop for piano wire...
Commonly used to make sprung undercarriage for model aircraft..(not the size you need you understand...)



They may have the size you need which is approximately 24swg..(0.56mm)

[Deko]

They may be a bit too small for what you need, but a good source of small compression springs are the retractable type ballpoint pens.

Cheers Dek.

[Jonny]

I used to be a spring maker one of three in the world but not torsion or expansion springs. It might be easier to use unhardened steel rather than the already hardened and tempered stuff you need to overbend.

There will be a lot of trial and error in the hardening and or tempering all steels work different, it will either collapse or break. Most modern stuff we had to harden in water and blaze off with whale oil which burns at 150 degrees.

Probably easier having a rummage through some tools, parts etc 1/4 o/d is common.

[jonesie]

sorry guys a miss spoke i meant to say music wire and not spring steel. guitar stings are good to make small springs,they need to be drawn at 400 deg.after making.http://www.deansphotographica.com/machining/projects/springs/springs.htm.this is a good site for how to do,worked good for me. jonesie

[picclock]

Hi Jonesie

That's a great site. Just reading that has given me much greater confidence. Corrected links are

http://www.deansphotographica.com/machining/projects/springs/springs.html

http://www.deansphotographica.com/machining/projects/springs2/springs2.html

There are also some interesting other projects on http://www.deansphotographica.com/machining/projects/projects.html

Will get hold of some guitar strings and give it a go - It looks really easy now I've seen the info. Interesting that the springs reduce in diameter after the heat treatment.

Many Thanks

picclock

[Jonny]

Thats only applicable to music wire where the finished job shrinks.
Its because the wire comes hardened and tempered, although soft compared to other materials its easy to bend as in collapsing and therefore stressing.
Bend it too far it wont spring back, ok for low load intermittent use.

In annealed state V and leaf springs set to a pattern will collapse a touch when pulled up after hardening and tempering. EN42 nearest modern equivalent but a bit soft.

Your car springs are a totally different entity, hardened after then tempered.
Best one ever seen due to cost was multiple parts actually casted in several moulds then taken to a spring maker to make good.

[jonesie]

hi picclock glad that site was a help. i just made a spring for my farmboy hit and miss,it needed to be .400od 1.05 long and 7 turns of .019 wire. i used  of piece of .017 guitar sting on a 6mm dia drill rod and it can out real close. then wrapped in steel wool and heated to 400 degs. and it works real good. good luck jonesie.

[picclock]

My apologies for revisiting this, its just that I am having some trouble with maths. I'm using a spring program http://www.efunda.com/DesignStandards/springs/calc_comp_designer.cfm#calc which should make everything easy but I'm struggling with the concept of a spring constant which is expressed in Newton Metres. I remember from my schooling days Hookes law about the force on a spring being a function of the length. So I want my spring to have a force of 13gms per mm (2mm=26gms etc). I just can't seem to get my head around how to convert that to Newton Metres - its the wrong type of unit (at least my head says it is) 

I'm clearly missing something here - perhaps an expert could point (simply) to the path of enlightenment ?

Best Regards

picclock

[Lew_Merrick_PE]

My apologies for revisiting this, its just that I am having some trouble with maths. I'm using a spring program http://www.efunda.com/DesignStandards/springs/calc_comp_designer.cfm#calc which should make everything easy but I'm struggling with the concept of a spring constant which is expressed in Newton Metres. I remember from my schooling days Hookes law about the force on a spring being a function of the length. So I want my spring to have a force of 13gms per mm (2mm=26gms etc). I just can't seem to get my head around how to convert that to Newton Metres - its the wrong type of unit (at least my head says it is)

I'm clearly missing something here - perhaps an expert could point (simply) to the path of enlightenment ?

Pic -- Be very careful with the stuff posted at efunda.  It is not that well vetted!  I have seen a couple of major disasters when people depend on equations coming from efunda.  Their units are often screwed up.

A spring constant is the force/deflection the spring supplies.  It would be given in N/m or lb/in, not N-m (that is either energy or torque).  In conventional engineering terms, the spring constant is designated by the letter k and the deflection of the spring (from its free length) is designated by the letter x.  Thus, the force applied by a (linear force) spring is F = kx.  The energy supplied by a (linear force) spring is E = 0.5k(x²).

Does this help?

[picclock]

@ Lew

Yes, that makes perfect sense, or at least lines up with my world view. The reason for using that site was that plugging in the numbers is likely to get me to a closer result more quickly, but from the look of it its just not that useable. I really wanted a program where I could enter the wire type/diameter, spring diameter, number of turns, length etc which would then tell me the spring constant (in a form I could understand). 

Thanks for the swift reply

picclock

[mklotz]

When I look at the page in the original URL, it lists the units for spring constant properly as N/m or lbf/in.

[picclock]

Hah - was just trying it with lb/inch and the site blocked me and wants membership and payment. Oh well it was an interesting visit while it lasted.

Many thanks for your assistance

Best Regards

picclock

[Lew_Merrick_PE]

Pic,

A coil spring is a rather complex device.  The (active coil) length of the spring is a torsion bar -- so you are dealing with polar geometry deflections, stresses, and strains rather than linear ones.  This is then complicated by the curvature of the coils (represented by the Wahl's Correction Factor).  The actual allowable stress in a coil spring is further modified by the material's Bulk Modulus.

The worst part is that I have a 1950's vintage (something like) Designer's Guild to Springs I used during my apprenticeship.  It is buried in the 100-150 unpacked boxes of my technical library.  The spring manufacturer's association used to give such things out for free to encourage people to use springs.  Now they charge more than $150 for that (now) proprietary intellectual property!

[AdeV]

Tutorial here: http://madmodder.net/index.php/topic,2734
and here: http://madmodder.net/index.php/topic,2747

[bob ward]

A lot of good info in Spring Design and Manufacture, #19 in the Workshop Practice Series

[Lykle]

Hemingway Kits make a nice little spring winder.

http://www.hemingwaykits.com/acatalog/Universal_Spring_Winder.html

It comes with various pieces of wire to make springs.

I know I want one.

Lykle

[Lew_Merrick_PE]

I took a minute and I believe this is a pretty nice site...

http://www.planetspring.com/pages/compression-spring-calculator-coil-calculator.php

[Fergus OMore]

Rolson Tools is where mine came from but Screwfix stocks boxed sets.

[Lew_Merrick_PE]

Here are two files (PDF's) you may find useful.