Specifiying a Spring

[Gold]

It's not electronics but is audio related. I would like to replace the spring in my Neumann lathes' cutterhead susspension box. It's probably close to 40 years old at this point. Does anyone know how one would go about figuring this out? I can come up with a spare if I need to send it to an expert.

 

[bcarso]

Work hardening and crystallization may have changed the spring constant significantly. Maybe there is someone who could make an educated guess at the material and deduce the properties.

 

[josh]

compression, extension, or torsion?

-Stainless, piano/music wire, or chrome vanadium
-diameter of the wire
-# of coils
-free length
-diameter of the cylinder
-right hand or left hand wind

then for extension springs what type of end fitting
and for torsion, the angle of the legs coming out and their length

that's it my friend, your dont need to know the spring constant, it is a function of all these things I listed.
mcmaster.com will make custom springs for about 20 bucks if you cant find the size you need from stock.
or you can try Century Spring, but 1 spring from them will cost you.

 

[Gold]

Thanks Josh. It all makes sense except for the free length. It is an extention spring and I suspect it has 'streched', which is the reason I want to replace it. How do I account for that?

 

[josh]

if it's an extension spring, the free length is going to be (probably anyway) the distance from outside loop end to loop end, if it has them.
Just take it off, close it all the way so any creep or fatigue that has set it will be irrelevant if you just hold it completely closed. Take your measurements and you're off and running.
Use calipers to measure the wire diameter too.

 

[Gold]

Got it. Thanks!

 

[josh]

:thumb:

good luck