A swivel base is a type of vise base that allows you to rotate the vise in a circle. Many vises come with this feature and it’s fairly simple to disassemble and reassemble. A wide variety of vises of different sizes have this feature.
Disassembling a swivel base vise
Remove the lock nuts by rotating them in an anti-clockwise fashion. Once they are off move on to step 2.
Once you have removed the lock nuts, you should be able to pull the vise off it’s base. If you look inside the outer base plate, you should see and inner base plate with two carriage bolts pointing upwards. It is this inner base plate that allows the vise to swivel.
And that’s it. It’s really that simple
Assembling a swivel base vise
To assemble the vise just repeat the above steps but in reverse.
Place the inner base plate inside the outer baseplate. Make sure the carriage bolts are all the way through the inner base plate; you may have to turn things upside down and use gravity to keep them in the right position.
Place the vise body on top of the outer base plate. Make sure the carriage bolts bolt into the vise body fully. Lock the locking nuts and you should be good to go.
If you were looking to modify a vise that wasn’t originally designed to be a swivel base vise, you should be able to reverse engineer based on the steps above. Note: most manufactures recommend against modding their vises.
If you are looking to buy a swivel vise, I review several in my 3 best bench vises guide.