I'm building a crosscut sled and want to ensure my fence is properly squared to the blade. I used three 3" wide strips of 3/4" Baltic birch plywood for the fence, about 32" long, and I glued them together with Titebond II, clamping them against a level. After checking for flatness with a straight edge and feeler gauges, I found a 0.007" gap in the middle. I'm wondering, before squaring the fence, does this amount of flatness really matter? Am I worrying too much about that 0.007"? How will any slight bend in the fence affect my ability to achieve square cuts? I'm particularly concerned about how this might compound as I work through the project, but if this was a final product, I'd be okay with it.
4 Answers
Just for perspective, 1/32" is 0.03125 and your gap is much smaller than that—less than a quarter of it. I wouldn’t stress over those 7 thousandths!
How straight is your reference surface? If you're using a reliable straight edge, like a 50" aluminum one that boasts a tolerance of 0.003", that should give you more confidence in your measurements. It’s essential to have a good reference to ensure accurate readings!
Yes, you're probably overthinking the 0.007" gap. It's pretty common in woodworking to allow for some minor imperfections. Most professionals consider anything under 0.010" to be acceptable for flatness, especially since it usually won't lead to larger compounding errors in your cuts.
In woodworking, that last digit on a micrometer isn't even a concern. You're within acceptable tolerance levels for furniture or general projects. Don’t let the small number push you to worry excessively.