As usual, click any photo to bring up a larger version.
I have a pretty compact basement shop. In order to make that work with my tools, I need to be pretty creative with storage, but even more importantly is that most things need to be mobile.
My jointer is on a mobile base. My bandsaws are mobile also. My planer and miter saw share a fliptop tool stand And of course, my tablesaw also needs to be mobile.
I built this mobile stand about three years ago and it has been an amazing asset to my shop. It adds a huge amount of storage to my compact shop, while maintaining the mobility of the saw. Finally, it does all that without increasing the footprint of the saw. I posted some photos and details about this stand last year on this webpage.
With that lengthy introduction out of the way... I have a problem with my mobile tablesaw workstation. The front horizontal rail is twisting, which is interfering with the bottom drawers.
Here is a closeup of the front rail, on the far right end. I have placed a small square on the rail. As you can see, the top of the square is touching the drawer front, but at the bottom of the square there is a gap of at least 1/4" in size. This is because the 2x4 which makes up the top rail of the base has twisted.
I'm very puzzled as to the cause of the twist. I do not believe that the weight of the mobile workstation is the cause, and here is why:
Here is a closeup of the back rail. Again, I have placed a square on the rail and it shows that there is no twist at all affecting the back rail. It is still showing a pretty good 90-degree angle between the top rail and the cabinet that it is carrying.
The top rail on both the front and the back are identical to each other. They were cut at the same time. The front and back of the mobile base are built in the exact same way. As well, the front and the back rails are carrying the same amount of weight. The workstation is not really weighted toward the front or the back.
I'm left thinking that this was just a "weaker" 2x4 than the back one. Perhaps this tree grew differently, perhaps there was more space between the growth rings (which would make it weaker, I believe) or perhaps it was just how the growth rings were oriented in the 2x4. I really just don't know.
Fortunately, I built this workstation in a modular fashion. I built it so that it could easily come apart -- either if I were to move, or if I were to wanto make a change to one part of the unit. Therefore, I set about taking the workstation apart. I saw two possible solutions. I could try adding some triangular angle braces along the front of the workstation. Or I could replace the bad top rail with a new piece of wood. I elected to replace the front top rail with some hardwood.
After removing the drawers and cabinets I "walked" the tablesaw out of the left side of the base, and then tipped it up to get it completely free of the base.
Back when I built the base, I glue the top rail to the vertical rail, in order to make it as strong as possible. However, I did NOT glue it to the plywood base. This was on purpose, just for this specific situation of having to take it apart.
However, I then added this sub-base on the right side, a sort of torsion box assembly, for a few reasons. This, was screwed to the front rails by means of some pocket holes from the inside. So I had to use a sledgehammer to "pursuade" the base to come apart. Here I am gluing in some new blocks, beside the inner torsion box ribs, so that I had fresh wood for later screwing the base back together. The original plywood was chewed up a bit by my disassembly.
Because I'm cheap, I did not want to use some of my nice large pieces of hardwood. Instead, I made use of two narrower pieces of ash, which I ripped down to pieces a bit over 1-1/4" wide. I then flipped these on edge and glued them up. By doing so, the grain lines were all oriented vertically. This would also hopefully help with the strength of the top rail, helping to prevent any vertical sag.
This piece was then jointed and planed to make it roughly the same thickness as a spruce 2x4, and trimmed to length to match the piece that it was replacing.
Here is a closeup of the end, showing how the grain lines on the end of this glued up piece are now oriented vertical.
And then it was time to put it all back together. Again I attached the vertical/horizontal rails to the plywood base only with screws, so that it could be cleanly disassembled in future.
This time I screwed into the torsion box platform part of the base from the outside!
As you can see in the photo, I decided on a "belt and suspenders" approach. Or to put it another way... I wanted to be absolutely certain that I had fixed the problem, so I added four diagonal braces on BOTH the front and the back of the base. So I added them to the section I repaired with hardwood, and I also added them to the other section (which still had a perfectly straight 2x4). I don't really think they were necessary, but it was an easy modificaiton to just help it a bit more.
And finally here it is back together.
What follows are some detail photos of the finished unit.