I had to make one of these for my DSC project. It's just as easy to make half a dozen as it is one, so I have 5 of these to offer. These are 1/2" 13 UNC bolts, 2 1/2" long. Threaded portion is 1 1/2" long, unthreaded portion is 1" long. The bolt heads have been drilled to accept 1/4" encoder shafts and have also been drilled and tapped for a locking setscrew (nylon thumbscrew also included). These bolts screw into a 1/2" 13 UNC nylock nut that has been welded to a steel plate that can be secured to the underside of your groundboard using four wood screws supplied by you. This makes for a very secure anchor point for the bolt. The nuts have also been drilled and tapped for a setscrew to lock the bolt in place if req'd.
These pivot bolts work for a Dob with a 3/4" groundboard, with 1/8" teflon pads and a 3/4" thick rocker box bottom. "The bushing and encoder in the picture are NOT included", they are for my application. Bushings or bearings can be easily obtained at industrial retailers for your application.
These bolt sets are sold AS IS for the nominal fee of $10.00 each plus shipping, which usually runs around $5.00 from up here in the Great White North. PayPal preferred.
Thanks for look'n and have a Great Holiday Season.