Monday, July 16, 2018

On precision...

On precision...  Do you know the best way to gauge the alignment between two pieces of wood?  This need comes up frequently in woodworking, and getting alignment wrong means (at best) a lot of sanding and (at worst) discarding a piece of work.  So what's the best way to determine whether two pieces of wood are lined up exactly?

Most woodworkers already know the answer, either from a mentor early in their woodworking efforts, or through hard experience.  I'm in the former camp, myself – my grandfather (father's side) taught me this simple technique.

Most non-woodworkers don't know this technique, and if asked to speculate, will usually come up with answer involving a known straight edge and squinting at how it sits across the joint that is supposed to be lined up.  That technique is difficult and quite error-prone – and isn't all that accurate anyway.  The best way actually involves no tools or instruments of any kind – just your finger!  All you do is run your finger across the joint to feel if there's a difference in height between the two pieces of wood.  Really!

A study five years ago determined that fingertips can detect surface details as small as 13 nanometers ( about 0.0000005 inches).  No instrument within reach of an amateur woodworker or cabinet shop can measure anything that small.

Your fingers are a marvel of texture-detecting design – better than anything mankind has ever been able to make...