Finall version of stop and lock (almost)
The Morton push-button nuts arrived yesterday and their diameter of 38 mm is a hair too wide to be threaded onto the scale bolt without removing the bolt, which I did easily enough. On the Jet JDP-17MF the scale bolt is a two-diameter threaded shaft, the top portion having a 16mm-2 thread, with a flat face milled out of 180 degrees of the diameter. The short section at the bottom is turned and threaded for a 10mm nut, which secures the bolt to the seat. If anyone wanted to replace the existing metric scale bolt with a length of SAE threaded stock, he or she would need to turn down a couple inches of the bottom end of the stock to fit the existing through-hole in the seat, and re-thread it for a hex nut of choice.
Once I got the two Morton nuts installed on the scale bolt, above and below the seat, I discovered the upper nut -the one for a stop - was interfering with the edge of the hex nut that secures the "Quill set screw" to the case. For reference, the hex nut at issue if Part #55 on the Jet exploded diagram and the set screw if Part #54. I was about to take a file to the hex nut and then decided I'd look up what I was about to deface a little. I have two parts diagrams. The older one is part of the manual that came with my press and shows two 7/16" lock washers (parts #607) stacked onto the shaft of the #54 set screw and held against the drill press case by the #55 hex nut. The newer parts diagram is part of a newer edition of the manual, one I downloaded recently from Jet's Website. In that diagram, the two lock washers are completely absent.
I called the technical support guy at Jet/Powermatic and asked him exactly what the "Quill set screw" did - and he didn't know. Incidentally, what I've been calling the "quill" until today is what Jet calls the "scale bolt" - Part #613. The "quill" is actually the much larger part through which the spindle of the press is installed. Mea culpa and please excuse my ignorance. In any event, he agreed that later versions of the press were made without the two lock washers.
The reason I go so tediously at this business of lockwashers and no-lockwashers on the quill set screw, is this: when the lock washers are removed, the hex nut moves away from interference with the new Morton push button stop nut and gives 2-3 millimeters of clearance, which is plenty.
When the push button of the Morton nut is released, the threads of the nut re-engage with the threads of the scale bolt and can be finely adusted by rotating the nut. However, there is no internal provision on the Morton nut to lock it in place. It holds some degree of spring tension on the thread of the bolt but I'm not sure how it will respond to the normal vibration of the press in use. I may be overthinking this but an easy solution for me, since I already had two Ruland set screw shaft collars on hand, was to drop one of them onto the top of the Morton nut and let it ride there until I had need to set the stop. After setting the stop with the Morton, the shaft collar can be locked with its set screw to keep the Morton nut from increasing the depth of the hole, which would be the concern if the nut moved from vibration. A shallower hole can always be checked and corrected. I need and have ordered a thumb screw for the shaft collar. I'll post some pictures after supper.