It's a 10mm lock nut but not sure about the thread pitch. I can tell you 
tomorrow. I have a couple in a bag
that I can check.
It should be  easy enough to find at a local 
hardware store. I wonder if the SW
has something to do with it being a
lock nut.

Bill

Sent from my iPhone

On May 8, 2013, at 9:25 PM, Bryan Feddish <uprightbassghost@HOTMAIL.COM> wrote:

> Can someone tell me the size of the nut (Item # 7 ) at the bottom in this picture?
> 
> http://tinyurl.com/cayakoz
> 
> Thanks,
> Bryan