Spring Inspection Method

[weisusu]

I would like to measure the outer diameter of a spring (0.130" ID and 0.030" wire thickness) at free state and measure the outer diameter again when it is compressed at 0.050". Any thoughts as to how to measure the outer diameter of the spring at compressed state? I'm interested to find out diametric expansion of the spring under compression.

 

[KENAT]

weisusu, if you must double post I suggest you put a link to the other forum, you may get red flagged otherwise.

thread1103-227624

KENAT,

Have you reminded yourself of faq731-376 recently?

 

[btrueblood]

Use a jig that holds the spring in compressed state and measure o.d. optically (e.g. optical comparator).

 

[kkg123]

dear Kenat

i am unable to find "thread1103-227624: Spring Inspection Method"

will you please elaborate the method discribed

Kedarg6500

 

[CoryPad]

It was deleted since it was a crosspost.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[KENAT]

It was your other identical post.

I think btrues idea has merit. Fundamentally have some kind of jig that compresses the spring then measure the OD.

Of course, the compressed spring may not maintain good cylindricity which you'll have to allow for.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[btrueblood]

Thanks Kenat. I had to make similar measurements to the OP's recently. The important thing is to build your jig to replicate (as best as possible) the configuration that you intend to use the spring in.

E.g - we had a piston spring for what was effectively a hydraulic cylinder. We mimiced the piston and end cap, and loaded the rod with weights below where it penetrated the end cap. We were also concerend about how much sideways deflection/moment might be created by the spring, tending to push the piston rod off-center, so we used a spherical bushing where the rod passed thru the end cap. This also allowed us to measure the sideways force required to re-center the piston/spring. Results were surprising to us...springs do not always behave as you might think.