Compression spring design 1

[WoodRunner]

Hello,

I am designing a tool that will hold parellels against the inside faces of a vise. I am having problem selecting the right compression spring. I do not know how to calculate the required load (a machinist should be able to fully compress it with one hand) in order to deternime the number of coils or materials to use or even wire diameter. My guess is that it should be resistant to typical CNC mill coolant. What I do know is that is should fit over 3/8 inch diameter tubing, a free lenght of 8.500 inch or more and a minimum working lentgh between .750 - 1.000 inch.

Thank you.

 

[Tunalover]

Any decent machine design text will go into spring design in detail. It sounds like you want the forum to design the thing for you.

Tunalover

 

[berkshire]

woodrunner
Why don't you take this to forum 693 spring engineering?
B.E.

 

[zekeman]

If you can get a copy of "Machinists Handbook" of recent vintage, their spring design chapter is one of the best IMO.

 

[WoodRunner]

Thank you for the help. I'll look into it.

 

[TheTick]

You need to figure out the loads for yourself. From the loads, you can determine the characterstics of the spring you need. What you probably will need to start with is the force the spring needs to exert at one or two given lengths. With forces at two lengths, you have determined the spring k-factor and preload. then you can try to find a spring that delivers your forces that fits in the space you have available.

Try this calculator:

http://www.engineersedge.com/spring_menu.shtml

 

[drawoh]

WoodRunner,

I keep a spring scale at my desk. If I want to figure out how much force to exert on something, one option is to pull on the spring scale. I can exert a force I feel comfortable with, then I can put a number on it.

JHG

 

[KENAT]

While it wont solve all your problems, you might want to look at a spring catalog from someone like Lee Springs and try and pick an off the shelf spring, at least for a prototype or one off if that’s the case.

Selecting how strong a spring you want can be surprisingly tricky. A colleague and I got it fairly wrong once and ended up with a tool that once closed was almost impossible to open. Not my finest hour, and this was done with a bunch of calcs to try and find the required load, I’m guessing we made a mistake in our assumptions somewhere.


KENAT,

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

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

What is Engineering anyway: faq1088-1484

 

[John2004]

There is a free compression and extension spring design calculator at the following link that may be helpful to you...

http://wwweng.uwyo.edu/commend/