Spring mandrel size

[fabricator]

Hey all, I am going to be making several .007 ID springs on the lathe from .080 music wire. Is there a general rule of thumb for calculating mandrel size?

 

[Asm109]

Empirical results will be most useful and real. ID of coil is 7 mils? is that a typo?

 

[fabricator]

Oh crap yeah it is, .700 is the ID my lysdexia is acting up I guess.

 

[Kevinb71]

Here is a link to Porter Spring. There is a 62 page pdf on making springs here. Hope it helps. Advance Car Mover Co. manufactures quality tools in the USA - Powered by Network Solutions.

 

[fabricator]

Wow, excellent! Thanks a lot!

 

[fabricator]

Here is a link to Porter Spring. There is a 62 page pdf on making springs here. Hope it helps. Advance Car Mover Co. manufactures quality tools in the USA - Powered by Network Solutions.

I checked the site map and I don't see the pdf.

 

[Steven Green]

Oh crap yeah it is, .700 is the ID my lysdexia is acting up I guess.

Machinery’s handbook gives 0.599 mandrel for 0.875 OD spring with 0.080 wire. You’re wanting 0.860 OD so I would try between 0.580 to 0.585.

 

[fabricator]

Thanks, I'll try it.

 

[chucketn]

Fabricator, try here: http://educypedia.karadimov.info/library/springs.pdf

 

[fabricator]

Just what I was looking for, thanks.

 

[kquiggle]

You might try my web page here (go to the link and search for "springs"):

https://sites.google.com/site/lagadoacademy/useful-links

 

[fabricator]

There is a lot of useful stuff there, thanks for the link.

 

[Richard Hed]

I checked the site map and I don't see the pdf.

iT's in smaller print at the end of a line which says something like "Here's some useful information"

 

[fabricator]

Ok thanks I'll look for it.

 

[fcheslop]

Thanks for the link Chuck
There is some useful info on making springs on Deans site
http--www.deansphotographica.com-machining-projects-projects.html

 

[Master]

Needed 10 springs for my Edward Radial rocker arms. Past experience making springs on my lathe have been inconsistent. Decided to make the spring winder by Dario Brisighlla in Issue #19 of Model Engine Builder. Had to experiment with the adjustments, but all ten came out perfect.

 

[TSutrina]

Spring back, the spring wound on a mandrel will upon stopping the coiling of the spring and releasing the end will uncoil a little and become loose on the mandrel, diameter increases to the final diameter. Not found a formula for determining this spring back. The bending process requires that the metal exceed the yield point. For metal the force and deflection of the steel is linear until the stress, force related to size and shape, reaches the yield point. Force flattens and the deflection from this point on is permanent which is added displacement on top of the linear displacement. Remove the force and the linear displacement removes.

 

[retailer]

I recently made a few springs with 0.125" ID, I tried a variety of wire diameters from 0.021" to 0.027" the wire came from a local family owned spring making business, they had no issues selling me a few meters of each wire size, I spoke to the guy in charge of the workshop about spring back allowance, he said there is no hard and fast rule, he works on around 10%, it will vary slightly with spring diam. and wire gauge and experience here does help. He suggested I use 10% as a starting point, if the spring back is too great then go down a bit on the size of the mandrel. They use cheaper carbon steel spring wire, rather than piano wire for all of their coiled springs, the springs are all normalised/heat treated after winding.