I have long relied on a steel straightedge to assure that anything that needs to be straight or flat is indeed straight or flat.
I have treated this steel straightedge very well, keeping it from direct sunlight to avoid warping and storing it where it would not be bumped or abused.
Today I was having a very difficult time leveling a fretboard. This is usually a straightforward task; I check the fingerboard with the straightedge and mark any high spots and plane them down.
I follow up the planing with a remarkably scary sanding block. The block is trued by planing and it’s straightness is also checked using the straightedge.
Once the fretboard is dead flat I plane and sand a bit of relief into the fingerboard. I check the depth and curve of the relief by placing feeler gauges between the straightedge and the fretboard.
After several failed attempts to get the fretboard dead flat I was perplexed; perhaps I was having a bad day, perhaps my sense of perception was off.
And then I thought that possibly “old reliable,” my trusty straightedge may have made the transition from accurate tool to annoying metal object.
And it had!
Both edges are no longer truly straight. They both have a bit of a wave to them. I don’t know what caused this to happen.
The mystery was solved but what to do now?
I have a 3 foot level that I have assumed was fairly true. I checked it and found that one side was dead-on straight! It’s a bit flimsy so I have to be careful not to flex it when using it as a reference.
The straightedge was expensive.
The level wasn’t.
When I bought the level I looked for the straightest one by placing them all against each other till I found one that seemed the flattest and most true by eye.
I think I got lucky!