Hey Mr. J.M.Scott,
I tried to PM you, but I haven't had much luck with that on this forum for some reason. Can you explain in more detail how you make the "mini-jack" with the bolt coupling? Thanks
Here is a jack that is made of 1/2" pieces. You will need one made with 3\8" because the small end on your pin is a hair smaller than 1/2". If you haven't already, drive the swivel jaw retaining pin out From the side. I would also clamp the swivel portion down so if the pin is stuck in the top part it will push it apart from the main housing and put pressure on the inside mating shoulders and possibly break them. The swivel could come out with pin still stuck in the top part. Good Luck !!
This issue has been talked about more then once so I dug out a Prentiss swivel Jaw vise that is a # 20, it actually had a stuck pin and this is my first choice on getting these stuck Swivel Pins out. First I add a plate that covers the dovetail nut support, you do not want to put any pressure on any cast with a small bolt head. My picture is fuzzy but there is a 1/4 flat plate held in by magnets. The next picture gives a view from underneath the swivel pin, the hole goes all the way through the Static Jaw Support. A 3/8 bolt fit pretty good in the clearance hole.
<a href="https://visejaws.smugmug.com/Vise-Repairs/i-ksR8nJW/A"><img src="https://visejaws.smugmug.com/Vise-Repairs/i-ksR8nJW/0/S/Pushing%20a%20Swivel%20Pin%20%281%29%20-%20Copy-S.jpg" alt="Photo & Video Sharing by SmugMug"></a> <a href="https://visejaws.smugmug.com/Vise-Repairs/i-KLp8xLR/A"><img src="https://visejaws.smugmug.com/Vise-Repairs/i-KLp8xLR/0/S/Pushing%20a%20Swivel%20Pin%20%283%29%20-%20Copy-S.jpg" alt="Photo & Video Sharing by SmugMug"></a>
Then I made a set up like GETRIDAONE did. I like the coupling type nut to give more strength and adjustment in the threads, fit the sawed end so you get as much threads for adjusting.
Then use two wrenches to push out the swivel pin, mine popped pretty easy.
<a href="https://visejaws.smugmug.com/Vise-Repairs/i-5WbVNSK/A"><img src="https://visejaws.smugmug.com/Vise-Repairs/i-5WbVNSK/0/M/Pushing%20a%20Swivel%20Pin%20%286%29%20-%20Copy-M.jpg" alt="Photo & Video Sharing by SmugMug"></a>
You can see some rust on the pin which is mostly the reason these pins get stuck.
<a href="https://visejaws.smugmug.com/Vise-Repairs/i-cHqHDRk/A"><img src="https://visejaws.smugmug.com/Vise-Repairs/i-cHqHDRk/0/S/Pushing%20a%20Swivel%20Pin%20%287%29%20-%20Copy-S.jpg" alt="Photo & Video Sharing by SmugMug"></a>
You might have to apply heat to the swivel jaw and Static Jaw Support if not successful. Do not heat the pin, heat the casting, you want the casting to grow not the pin. Yes the pin gets hot but for a minute or two the casting will grow some.
If this does not work then drilling the largest hole possible that is a little under size the clearance hole where the push pin is. For my vise a .390 hole drilled in the center of the pin would be the biggest I'd use and it would relieve some pressure. If this still doesn't work then a slide hammer welded to the top should do the job. Good luck reivertom, let us know how how you did.