I've recently made several mobile bases for several machines. I've used either 3" or 4" Home Depot locking casters, and they've been great. I've made the bases from 1 1/4 inch (planed down) southern yellow pine boards glued together. I've done this with a 6" jointer, a 17" floor standing drill press, and a stand for a lunch box planer. The casters are well made and roll very smoothly. Locking two casters provides sufficient staying power to use the machine. The mobile base is particularly useful on the drill press. For one thing, it raised the drill press by about 5 1/2 inches which is much more comfortable for me. I suspect these type casters wouldn't work with extremely heavy equipment, but they worked just fine with a Jet combo sander. I built a box stand for this sander. Total package probably weighs 350 pounds. I used 4" casters from Home Depot. It rolls very nicely.
With the drill press, that's kind of scary, isn't it? What I did with mine (Nova Voyager) is bolt it thru a steel plate to a Portamate 2500, which actually _lowers_ the center of gravity and enlarges the footprint somewhat. I wouldn't want this top-heavy bad boy tipping over. The working height is controlled by the table, unless I'm missing something here. The 2500 is inexpensive, and works very well.
Doug,
You've asked some good questions. My homemade mobile base is about 2 1/2 inches longer and wider than the base of the drill press. The 4" casters I used sit slightly outside the drill press base. This actually results in more stability than the drill press without the base. I don't experience any side-to-side sway with the mobile base. You are correct that the table can move up and down. The point I was trying to make (but probably not made clearly) is that the working height - that is, where I would generally be working with a standard sized work piece and standard sized bit - is higher (about 47"). I have a lower back problem. When I can work without having to stoop or bend, I am much more comfortable. I can also see the work piece better at that height.
Best wishes,
Jay
Last edited by Jay Kepley; 10-21-2019 at 4:00 PM. Reason: Add Pictures
The base I made for my old 15" drill press also sits on a base wider and longer than the metal one, similar to Jay's. Castors are out further in both directions, never had an issue in years. Randy