what size nut on mac 12t

[rmasu]

Hi, I hope this is not a dumb question. I ordered a mac 12t motor on advice from this forum and laced it to a 26 inch fat tire rim.
The drop outs on the front fork are so wide there is a huge gap between the motor face and the fork. I currently have a stack of washers in there and it seems to be ok, but I think another bolt on the inside of the drop out would be a lot safer. I have one side locked in with a anti drop out arm bolted to the fork. I went to 3 different hardware stores looking for the same bolt, home depot lowes and a local shop. Cant find the proper size. It seems to be metric somewhere between a 13 and 14 size, I dont know what pitch. Can someone help with a size and a possible source to obtain one?
Thanks

 

[spinningmagnets]

The threads on the axle are 14mm X 1.50

I "think" it may be the same as some metric car lugnuts?

http://endless-sphere.com/forums/viewtopic.php?f=16&t=51310

 

[rmasu]

thanks Ill look into that or do a search online the 1.50 is the twist I think, most metric pitches in our hardware stores is 1.25.