The desire for a straight knurl on a small part led to borrowing one wheel from my regular diamond knurling setup for temporary use in this holder.  The bar simply has a flat machined with a tapped hole for a shoulder bolt.  The thick washer on top might not have been strictly necessary.  In use the bar is inserted into the boring bar holder of the quick change tool holder.  It's rotated to bring the grooves from the diamond knurl into the horizontal plane.  I'm not sure if this is the RH or LH wheel, but it's whichever one will work correctly in this position.  Okay, if I'd pulled off the other wheel I could have simply rotated the bar in the other direction.  Works like a champ.