Making it Mobile (but Stable)
After I bolted the top to the stand, I encountered a problem: the bench was solid, but it wobbled. Three legs touched the floor, but one hovered slightly above it-not by much (less than 1/8"), but enough to be annoying.
No problem, I thought. I'll just trim the longer of the two front legs. So I made a little jig to support my router so I could use a flat-bottomed straight bit to nibble off the end.
That didn't take long and worked very well.
I flipped the bench back over and patted myself on the back. The wobble was gone. But… I moved the bench back to its storage location. It wobbled worse than before. I know I don't plan to work on it there, but still, I don't want it to wobble. That's embarrassing.
At that point, I realized that trimming the legs was useless, because different legs would need to be trimmed by different amounts depending on where the bench was. I needed another solution, but I decided to worry about it later, and concentrate on adding the casters so I could move the bench around more easily.
I've seen a variety of mechanisms for making workbenches movable:
I decided to go with a variation of the first design. I thought it offered the best combination of solidity and simplicity. I started by making the caster boards flip to the outside of the bench, as in the Schwarz videos above. That worked well. I placed the casters so they were directly under the legs, where they are most stable. I didn't think I'd need the latches featured in the second Schwarz video. I thought the bench looked a little goofy when parked, with the caster boards and casters in full view, but I left it like that while I revisited the wobble problem.
I know that the simplest (and cheapest) solution to the wobble was a shim or two, but I didn't want to use (and keep track of) shims. I wondered about thick rubber pads under the legs. Maybe they'd allow the bench to conform to uneven spots on the garage floor. But then I found these Heavy Duty Lifting Levelers
at Rockler and decided to try them. The best things about them for me were that they were relatively compact, could mount on the side of the legs, not under them, but still had a lip that would curl around under the leg (for strength). You adjust the height with an Allen wrench that fits into a socket on the end of the leveling bolt.
The levelers would fit on the insides of the legs, under the shelf, but it would be hard to get an Allen wrench in there to adjust the height. So I decided to change the casters to flip to the inside and put the levelers on the outside. That would look better.
To make that work, I had to move the casters away from the ends of the caster board so they would clear the stretchers. I worried that that would make the bench less stable when I moved it. It did, but it wasn't too bad. But now I encountered another problem. Any time I rolled the bench along its length, the caster boards would collapse inward, and the bench would fall to the ground. Not good… I'd need latches after all. I remembered seeing latches for sliding patio doors before. (One piece mounts to the door, the other to the jamb, and a U-shaped bar slides into holes in both.) I was able to find them at Home Depot.
Here's how it all turned out. I used screen door hinges to mount the caster board to the insides of the legs. I offset the hinges so the knuckles would rest on the floor when the caster board was folded up. (I still don't understand why Schwarz had to cut notches for the knuckles in his implementation.)
This photo shows how I had to move the casters closer together to clear the stretchers.
I had to cut shallow notches to mount the levelers. I used my router and a 1/2" rabbet bit for that.
Before moving the bench, I flip the caster boards down and slide the locks into place.
When the bench is parked, the sliding U-shaped part of the lock hangs there unobtrusively.
I'm happy with how it all works. The funny thing is that I don't need to use an Allen wrench to adjust the levelers. I can just rotate the bolt with my hands (it never has to move very far to contact the floor). So I could have left the casters so they flipped out and mounted the levelers to the insides of the legs.
I still think it looks better now, but I'm not sure I'll be able to use the bench in "tall mode" with its wheels down and locked due the the close spacing of the casters. Oh well…
If I had to do it all over again, I might opt to use very low-profile ball casters
and still make the caster boards flip to the inside. Then I don't think I'd need the sliding locks at all.