OK, thanks. Once it is parked, it won't be moved very often if ever. I just don't want to load it up and have the casters collapse.
Pretty sure when they give a load rating for a caster its limit is the rubber tire or the axle. If it is a swivel caster, the limit may be the swivel pin, since that is typically offset from the axle. Point is, I don't think any of these are typical failure modes for tool boxes.
The sheet metal box and specifically the base where the casters attach is usually the weak link.
1) If you are intending to load every drawer to its max with boxes of nails, nuts, and shot gun shot, buy a Lista. Otherwise, normal tools, stored properly, can't typically reach the maximums on every drawer. Wrenches can be heavy, and I have maybe 50-100lbs worth of sockets. So you have to watch those drawers. I feel more comfortable with a socket drawer with at least 100b capacity if it is 40" wide.
2) I've seen boxes crumble from being overweight. The bottom buckles, the side pillars in the front cave in and the box collapses. One thing you can do for yourself is reinforce the bottom to stop the sheet metal from buckling. W
Start by reducing the point loads where the caster base plates meet the sheet metal bottom. Even if the bottom has reinforcing members around its periphery, this is usually insufficient. Start by cutting a good piece of 3/4" plywood and nesting that to the underside of the box. That spreads the load from the footprint of the casters more evenly across the bottom. I saw boxes guys in our factory use 1/2" aluminum plate (back when they had their own boxes).
Sometimes there is space above the floor beneath the bottom drawer on the inside. I floated aluminum angles in there, running front to back and attached my casters up through them. That provides an enormous amount of stiffness to the base.
3) Boxes can easily rest most of their weight on 2 casters with just a little on the third. That's why the suspension casters are best. Place shims under the wheel that don't seem to have much weight on them.
