Reader: “How flat does my workbench need to be?”
Me: “Flat enough to work.”
Reader: “But how will I know when it’s not working?”
Me: “You will know.”
And really, that is all there is to say about the topic that is meaningful. But as this is a blog, I am going to add some more words so you feel you are getting your money’s worth.
Workbenches don’t have to be all that flat to function well. Even if you have significant low spots that you can detect with your hand or eye, the bench can still be perfectly functional. Why? Several reasons.
We don’t use all of the benchtop surface for high-tolerance work. Consider the areas where you handplane things. That’s your “special place.” It needs to be flatter than the areas you don’t use. Example: I don’t have a tail vise on my oak workbench, so I don’t care about the extreme right end of the benchtop.
Second: The wood we work is stiff. So even if your special place is wonky, a typical 3/4”-thick board will behave just fine there. (Plane an 1/8”-thick board there and you will have a different experience; but I don’t plane 1/8”-thick boards on a benchtop.)
Last week, my oak workbench stopped functioning. My special place was in disarray. What had happened was this: The top had shrunk, and so the end grain of the front left leg was interfering with the planing stop. I knocked down the end grain of the leg with a jointer plane in less than five minutes, and my special place was ready for work. But because I am mostly Teutonic, I was compelled to dress the rest of the top.
It took four passes with a jointer plane to true the top back to a state that is overkill.
I also had a small gap appear up near the planing stop. This has happened on many slab benches I’ve built before. I pushed some epoxy into the gap, a procedure I have covered many times over at my blog at Popular Woodworking.
Total elapsed time: About 45 minutes.
But that’s not the end of the story. During the summer I brought my daughter’s slab workbench back into my shop to use it for photography for “Campaign Furniture.” I haven’t flattened its benchtop for three years. It has been working fine, but I became curious and picked up a jack plane…
And now this blog entry is too long. I’ll finish it later. I have a date with a creepy janitor.
— Christopher Schwarz