What is this washer?

I am sorry that it may not directly relate to PLC.
I have this "washer" from an automation machine (which is controlled by PLC )
Two of these washers were put together (face to face) and connected to a pneumatic cylinder. Would anyone please tell me the name and the functions of this washer?

Also, would anyone please suggest me some website/forum which may discuss automation machine other than just specifically PLC like this one?

Thankssss

"Nord-Lock" washers, used in high vibration applications.

http://www.google.com/#sclient=psy-...48,d.cGE&fp=d3c2e672e36ecc9b&biw=1582&bih=807

http://www.youtube.com/watch?v=mgwmuZuJ02I

Tofo said:

... please suggest me some website/forum which may discuss automation machine other than just specifically PLC like this one?

Thankssss

Click to expand...

Broad category. Are you looking for general info on the industry?
Machine shop forum.
Automation World Magazine.